Pseudomonas aeruginosa infection in cancer patients.

Cancer Investigation, 10(1), 43-59 (1992)

INFECTIOUS COMPLICATIONS OF CANCER Ronald Feld, M.D., Editor

Cancer Invest Downloaded from informahealthcare.com by McMaster University on 01/08/15 For personal use only.

Pseudomonas aeruginosa Infection in Cancer Patients Kenneth V. I. Rolston, M.D. and Gerald P. Bodey, M.D. Section of Infectious Diseases Department of Medical Specialties The University of Texas M. D. Andersan Cancer Center Houston, Texas

INTRODUCTION

are also becoming increasingly important, particularly in patients with cancer. This review, however, will be limited to infections caused by P. aeruginosa.

Pseudomonus aeruginosa was first isolated in 1882 by Gessard, first recognized as a pathogen by Charrin in 1890, and is the most frequently implicated species of the genus Pseudomonus in human infection. Uncommon before the introduction of the sulfonamidesand penicillin, P. aeruginosa is currently the fourth most common cause of gram-negative bacteremia in the United States (1). It is responsible for approximately 10-12% of bacteremic episodes that occur in community-based hospitals, while in large tertiary care centers it accounts for about 15-25 % of such episodes. Among certain debilitated patient populations such as burn victims and patients with neutropenia, P. aeruginosa has been a leading cause of infection and is associated with significant morbidity and mortality in the immunocompromisedhost. P. aeruginosa causes a wide variety of diseasesranging from superficial infected wounds and bums, urinary tract infections, to such deep-seated and disseminated infections as bacteremia, endocarditis, meningitis, and osteomyelitis. These organisms are occasionally isolated from the skin and feces of humans and are frequently isolated from moist environmentalsou~cesincludingthe hospital environment. Infection can therefore be either exogenous or endogenous in origin. Other Pseudmnus species such as P. putida

EPIDEMIOIDGY Pseudomonas aeruginma is an obligateaerobic, motile, gram-negativebacillus. It elaborates fluorescentpigments that may produce a characteristicgreenish color at infected sites such as bums and wounds. It has been isolated from soil and water, and, in fact, thrives in moist environments. It has been shown to survive in water for up to 300 days and has the ability to proliferate in d i d l e d water (2). Because of this ability it has been associated with epidemics caused by Contaminatonof ophthalmicpreparations, aerosols, soap solutions, shampoos, humidifiers, and of equipment such as respirators, faucets and sink drains, shower stalls, hydrotherapy tanks,and water pitchers. Recognition of these potential sources of contamination has led to the formulation of careful guidelines regarding sterilization procedures, which have helped reduce their importance as major vehicles for the spread of infection. Pseudomnus aeruginosa has also been found to contaminate fresh vegetables before delivery to hospital. 43

Copyright 0 1992 by Marcel Dekker, Inc.

Rolston and Bodey


44

In one study the organisms were cultured from cabbage, carrots, celery, cucumbers, endive, lettuce, onions and mrnatoes delivered to hospital kitchens (3). Approximately 80% of the tomatoes were contaminated and it was estimated that a patient eating a standard portion of tomato salad would ingest 5 x lo3 P. ueruginosu organisms. The clinical significance of this observation is unclear since studies have demonstratedthat intentional ingestion of less than 103 organisms did not result in their detection in fecal material. Since antibioticprophylaxis or treatment can alter endogenous microbial flora this might facilitate colonizationby ingestedpseudomonas organisms in contaminatedfoods. However, the recommendationby some authorities, of denying neutropenic patients fresh fruits and vegetables seems rather harsh, and documentation of the adverse effects of eating such foods should be demonstrated before this dictum is universally accepted. Only 6 1 2 %of healthy individuals aR carriers of P. uerugirwsu, whereas 40-50 % of hospitalizedpatients may become carriers. The carrier state depends upon several factors including the nature of the patient’s illness, the duration of hospitalization and the pressure of antibiotic therapy. In a study conducted at the Baltimore Cancer Research Center, 190 patients with cancer underwent twice weekly surveillance cultures from various clinical sites including the nose, axilla, gingiva, urine, and rectum (4). P. ueruginosu was isolated from at least one site in 30%of patients, with colonization being highest in patients with acute leukemia and other hematological disorders. Pseudomonas septicemia was more common (21%) in patients who were colonized than in those who were not colonized (7 %). Also, 42%of the 29 colonized patients who were neutropenic ( c lo00 neutrophils/mm3) became bacteremic compared with none of the 28 who were colonized but were not neutmpenic. The role of antibiotic administration was demonstrated by the fact that 32 % of patients receiving antibiotics developed septicemia compared with only 10% of patients who did not. In another survey done at the M.D.Anderson Cancer Center, of 87 patients hospitalized with leukemia, P. uerugirwsu was recovered from throat or stool specimens of 25 % of patients on admission, and from 47 % after 2-4 weeks of hospitalization (5). Of the colonized patients, 26 % developed pseudomonas infection, in contrast to only 13% of patients who were not colonized. These data indicate that the risk of infection is significantly greater in colonized patients. There is also evidence to indicate that the longer a patient remains in hospital, the greater is the likelihood of colonization with P. uencginosu and other gram-negative bacilli. In addition to this, patients

colonized with P. ueruginosu are at particular risk of developing pneumonia if they require a tracheostomy or the use of a respirator. Patients with cancer who are most likely to develop infection with P. aeruginosu are those that are profoundly neutropenic as a result of their disease such as acute leukemia or as a result of antineoplastictherapy. In one series of 67 patients with underlying malignancies who developed bacteremia with P. ueruginmu, 81 % had an absolute neutrophil count of < 1000/mm3(6). Although profound and prolonged neutropenia occurs most often in patients with hematologic malignancies and recipients of bone marrow, patients with solid tumors are also being treated with increasingly immunosuppessivetherapies which render them neutropenic and at risk for developing pseudomonal infection. Pseudomnus infections are also becoming increasingly common in cancer patients who are not neutropenic, presumably because of selective pressures exerted by the extensive usage of antimicrobial agents in cancer treatment centers (Table 1).

Virulence Factors The pathogenesis of pseudomonas infections is complex. Like other gram-negativebacteria P. uerugiiwsu has a cell-envelope structure consisting of an outer membrane, a peptidoglycan layer, and an inner cytoplasmic membrane. The outermost layer is a polysaccharide layer of slime. These different components produce a number of virulence factors with invasive and/or toxigenic properties that help propagate infection and by producing

Table 1 Conditions Predisposing to Pseudomom Infection in Patients with Cancer Condition

Most common infection(s)

Neutropenia Leukemia Chemotherapy

Bacteremia, perirectal infection, typhlitis

Cancer

Pneumonia, bacteremia

Tracheostomy/respiratory lavage

Pneumonia

Vascular catheterization

Suppurative thrombophlebitis, bacteremia

Urinary catheterization

Urinary tract infection, bacteremia

Antibiotic usage

Bacteremia, pneumonia

Pseudomonas aeruginosa in Cancer Patients

Tabk 2 Virulence Factors for Pseudomas aeruginosa Biologic effect@)

Extracellular f i t o r s Exotoxin A Phospholipase and glycdipid


Proteases

Intracellular factors Lipid A Lipopolysaccharide “0”antigen Mucoid polysaccharide

Pili Slime polysaccharide

Cellular damage, toxic to macrophages Destruction of pulmonary sufactant Tissue invasion, cellular damage, inhibit complement-mediated defense and IgG cleavage Endotoxic effects Possible inhibition of phagocytes Antiphagocytic effects, decreased pulmonary clearance Adherence to epithelium Toxic to neutrophils, endotoxin-like effects

Source: Adapted from Ref. 61.

different effects on host defense mechanisms. The most important virulence factors are listed in Table 2 (7). The extracellular enzyme exotoxin A, is produced by most clinical isolates of P. aeruginosa (8). In a manner similar to the action of diphtheria toxin, exotoxin A inhibits protein biosynthesis by interfering with polypepti& translocation on messenger RNA (9). Purif~edexotoxin A is highly lethal, producing shock in dogs and rhesus monkeys (10,ll). In bacteremic human infections, toxin producing Pseudomoncls strains h v e been associated with greater virulence than nontoxogenic strains, and patients with high levels of serum antibodies to exotoxin A are able to survive Pseudoimm septicemia better than patients with low antibody titers (12,13). Phospholipase and glycolipid are heat-labile substances produced by P. aeruginosa that act together to break down lipids and lecithin (14). They cause the destruction of pulmonary surfactant (the major component of which is lecithin) resulting in atelectasis and other pathologic changes in the lungs. Phospholipase is also produced by urinary tract isolates of P. aerugimsa and might facilitateurinary tract infection as well (15). Several extracellular proteolytic enzymes are produced

45

by P. aeruginosa. These proteases destroy collagen, dissolve elastin and fibrin, and liquefy gelatin. Dissolution of the elastic lamina of blood vessels results in hemorrhage and destructive cutaneous vascular lesions (ecthyma gangrenosum). Hemorrhages into internal organs, particularly the lungs, during pseudomonal infection are also probably triggered by proteases (16). Proteases may also alter host defenses by inactivating complement factors and facilitating the cleavage of IgG. In addition to exotoxin A, the factor most likely to be responsible for the systemic toxicity of P. aeruginosa is its lipopolysaccharide(endotoxin). Many of the biological activities of endotoxin are mediated by the lipid A component of lipopolysaccharide. Circulating endotoxin appears to be important in the production of various manifestations of disease including fever, hypotension, oligurid, adult respiratory distress syndrome (ARDS),and disseminated intravascular coagulation PIC). It has been suggested that the endotoxin produced by P. aeruginosa is less potent than that produced by other gram-negative bacilli, but these differences are likely to be very small, and there is some evidence to suggest that the endotoxin of P. aeruginosa and those of other organisms are comparable in potency. Pili are protein structures that enable an organism to adhere to surfaces. These pili or fimbriae project from the surface of P. aeruginosa (and other gram-negative bacteria) and are responsible for the adherence of the organism to the upper respiratory epithelium of seriously ill patients (17). Cellular injury may also play an important role in the initial attachment of P. aeruginosa to epithelial cells. Injury of cell surfaces such as that produced by endotrachaelintubation facilitates adherence and is an important step in the pathogenesis of infection with P. aeruginosa (18). Another important component, the slime layer (glycocalyx, mucoid substance), is located in the outermost part of the cell, and is composed of protein, lipid, nucleic acids (both RNA and DNA), hyaluronic acid, and polysaccharide (19). It acts as a capsule and protects the organisms from toxic host factors (phagocytic cells, antibodies, complement),may mediate bacterial attachment, and may also have a direct antiphagocytic effect (20).

Host Defenses Pseudomom aerugimsa rarely causes disease in normal, healthy persons. In most cases alteration or circumvention of normal host defenses is necessary in order to initiate the disease process. Patients with malignancies may have several impaired host defense mechanisms

Rolston and Bodey


46

which predispose them to developing Pseudomonas infections. The most important of these predisposing factors is neutropenia. In addition to a quantitative defect ( < 5001 mm3), neutrophils may be functionally defective despite normal or enhanced numbers, or abnormalities may result from the interaction with serum factors or bacterial products. Examples of these included functionally defective neutrophils in patients with chronic leukemia, the blocking of bactericidal activity by IgG antibodies in patients with chronic pseudomonas infection, abnormal phagocytosis and intracellular killing by phagocytic cells from patients with cystic fibrosis, and the toxic effects of slime glycoprotein on granulocytes (21). The importance of phagocytic cells such as neutmphils has been studied by using P. aeruginosa isolates recovered from bacteremic patients. More than 90% of these isolates were resistant to serum and to autologous convalescent phase serum containing high antibody titers. However, the addition of normal polymorphonuclearleukocytes to serum resulted in a 10- to 100-fold increase in bacterial killing (22). Other phagocytic cells, such as monocytes and macrophages also play an important role in protecting the host against P. aeruginosa bacilli. Pulmonary macrophagesare particularly important in pulmonary host defense (23). Exotoxin A liberated by P. aeruginosa is toxic to human macrophages and results in cell death (24). There is some evidence that humoral immunity may be important in resisting pseudomonas infections. The production of antibodiesto bacterial cell components and toxins has been shown to correlate with survival in patients with pseudomonas infection. In one study, titers of serum antibodies to exotoxin A and type-specific polysaccharide were measured in 52 patients with P. aeruginosa bacteremia (25). Survival was greater (76%of 17 patients) in patients with high antibody titers than in those with low antibody titers (46%of 24 patients). A protective effect of antibody to the polysaccharide, was also noted. The protection afforded by those two antibodies appears to be independent and additive. In the group of patients studied, a significant antibody response occurred despite the presence of rapidly fatal underlying disease, leucopenia, steroid administration, and immunosuppressive drug therapy. The complex system of serum proteins that constitutes the complement system plays an important role in the ability of the host to protect itself against infection. Activation of complement is often initiated by immunoglobulins and proceeds via the sequential activation of components of the classic or alternative complement pathways. Both these pathways can be involved in the op-

sonization of P. aeruginosa. Antibodies seem to initiate the complement opsonization of most strains, although some strains can be opsonized by complement in the absence of antibodies (26). Properdin, the proactivator of the third component of complement, and “ ~ t u r a l IgG ” antibodies seem to be essential factors required for the killing of P. uenrginosa (27). Low properdin levels have been reported in patients with cancer, a population especially susceptible to pseudomonas infection (28). Phagocytosis of P. aeruginosa by pulmonary alveolar macrophages also appears to be mediated by the complement systems, and the termid components of this system are critical for the bactericidal function of serum. Cell-mediated immunity has been studied less extensively than other immune functions but there is some evidence to suggest that it may be an important defense mechanism against P. aeruginosa (23). The virulence of P. aeruginosa is enhanced in animals infected with cytomegalovirus which depresses lymphocyte-mediated immunity. T-cell dysfunction can also have an effect on humoral immunity and antibody production since many B-cell responses are influenced by T-cells.

Important Site of Psedomonas Infection in Cancer Patients (Table 3) Skin

Pseudomonas aeruginosa usually is not found in areas of normal, dry skin but thrives on moist skin. Cancer patients with or without P s e u d m n a s bacteremia may develop various cutaneous manifestations. One characteristic lesion, nearly always caused by P. aeruginosa is ecthyma gangrenosum. These lesions are commonly found in the axilla, groin, and perianal region, but can occur anywhere. They begin as painless red macules that enlarge into hemorrhagic purplish bullae, which frequently rupture and form ulcers with an edematous, erythematous halo. Single or multiple lesions at various stages of development might be present, occasionally with extensive tissue damage. Histologically, the lesions represent a bacterial vasculitis without thrombosis with dense bacillary infiltration of the media and adventitia, but not the intima, of the blood vessels (29). Experimental evidence suggeststhat these lesions may arise from hematogenous dissemination or from local invasion of the skin. One recent report describes 6 patients with hematological disorders, all of whom had P. aenrginosu isolated from skin lesions typical of ecthyma gangrenosum, but were not bacteremic (30). These patients had a significantly lower mortality than bacteremic patients with ecthyma gangrenosum.


Table 3


Important Sites of P. aeruginosa Infection in Patients with Cancer

Skin Ecthyma gangrenosum Gangrenous (necrotizing) cellulitis Head and neck Orbital infections External otitis Sinusitis Oropharyngeal infections Gastrointestinal tract Typhlitis Perirectal infection Respiratory tract Urinary tract Blood Bacteremia

Disseminated infection

Another cutaneous manifestation of infection with P. aeruginosa is gangrenous (necrotizing) cellulitis. This soft tissue infection is characterized by rapid progression with diffuse erythema and the development of gangrenous necrosis of subcutaneoustissue and overlying skin. Once established, gangrenous cellulitis can run a fulminant course and progress relentlessly toward death, particularly in immunosuppressed, neutropenic patients (31). In such patients surgical intervention is often necessary in addition to antimicrobial therapy. A common pmctice among cancer patients receiving chemotherapy is to shave their heads for aesthetic and/or emotional reasons, because some chemotherapeuticagents cause substantial but not total hair loss. Of interest is a recent report in which two patients with acute leukemia and severe neutropenia developed scalp infections due to P. aeruginosa, that had been acquired from contact with contaminateddiluted shampoo (32). One patient developed only localized infection in the form of a maculopapular rash and folliculitis. The other patient, however, went on to develop disseminated disease with cavernous sinus thrombosis and disseminated intravascular coagulation. She expired and autopsy revealed invasion of almost every organ including the brain, by P. aeruginosa. These two episodes led to the recommendation that patients hair be clipped prior to the development of severe neutropenia and that contact with potentially infectious materials such as shampoo be avoided. Two other situations have been described with in-

47

creasing frequency in recent years and may represent potential hazards in immunosuppressed cancer patients. The first is the increased incidence of P, aeruginosa keratitis associated with hydrogel contact lens wear. Situations that predispose the eye to infection include the use of ill-fitting lenses resulting in damage to the corneal epithelium, and improper hygienic practices such as the use of contaminated solutions among contact lens wearers. P. aeruginosa and Serratia murcescens are the most common gram-negative bacilli infecting corneal ulcers. The infection spreads rapidly and if not treated properly it may progress to panophthalmitis. With the increased popularity of contact lenses the incidence of keratitis is also likely to increase. Contact lens wearers should be given instructions regarding the proper maintenance of their lenses and ocular solutions, especially if they are immunocompromised, since the outcome of infection in such patients can be disastrous. Pseudomonas aeruginosa has been implicated as the causative agent in outbreaks of folliculitis associated with the use of contaminated hot-tubs, whirlpools, spas, and swimming pools. The lesions are usually pruritic, maculopapular, and erythematous, and occur most often in areas covered by bathing suits. Fever is uncommon and occasionally symptoms such as earache, headache, dizziness, and sore nose and throat may occur. Usually the infection is self-limited and resolves spontaneously upon discontinuationof exposure. The potential for dissemination exists in neutropenic cancer patients and it might be prudent to treat them with antipseudomonal therapy. With the increased emphasis on early discharge and improving the quality of life in cancer patients (as well as other patients) hot-tub or whirlpool-associated P. aeruginosa folliculitis does represent a new hazard. Head and Neck

Pseudomows aeruginosa is capable of causing both minor and serious infections of the head and neck. Involvement of the eyes and surrounding structures can result in localized infections such as conjunctivitis, dacryocystitus or orbital cellulitis. Blepharoconjunctivitisoccasionally is seen in cancer patients receiving chemotherapy (33). The patient usually has associated bacteremia and the orbital infectionprobably is the result of hematogenous dissemination. If not recognized and treated promptly progression to panophthalmitis can occur. Colonization of the external auditory canal by P. aeruginosa is not uncommon and more than 70% of cases of otitis externa are caused by P. aeruginosa (34). Malignant otitis extema is the most serious pseudomonal infection in elderly diabetic patients. There is, however, a

Rolston and Bodey


48

small but significant group of nondiabetic persons, particularly children with immunosuppressivedisorders such as malignancy, neutrophil chemotactic disorders, and occasionally chemotherapy or drug-induced leukopenia, in whom malignant external otitis develops (35). The salient features are severe and unrelenting otalgia, headache, edema, and tenderness of the soft tissues of the ear accompaniedby 50-80 % of cases by purulent otorrhea (36). Granulation tissue is usually present in the external auditory canal and histology usually reveals the presence of nonspecific inflammatory changes. If infection spreads, a large number of serious complications can arise including cranial nerve dysfunction, brain abscesses, mycotic aneurysms, sphenoidal sinusitis, parotitis, and lateral sinus and sigmoid sinus thrombosis (37). Meningitis is a very rare occurrence. Despite the administration of prompt antibiotictherapy, mortality is in the range of 20-25 % , and recurrences are not uncommon. Pseudomonas aeruginosa is rarely cultured from the mouth. Periodontal disease which can progress to osteomyelitis has been reported in leukemic patients. Ulceration of oropharynx, tonsils, and buccal mucosa, with the formation of an extensive necrotic membrane mimicking diphtheria, has been described. P. aeruginosa has also been described as an important cause of bacterial sinusitis (38).

the overall outcome when combined with appropriate antibiotic therapy but clinical data are scant and many investigators recommend conservative medical management alone (41,42).

Gastrointestinal Tract

Urinary Tract

Several types of pseudomonas infection of the gastro-

intestinal tract have been described. Typhlitis is a necrotizing colitis that is frequently localized to the cecum (39). It is primarily a disease of neutropenic patients, particularly children with acute leukemia. Although P. aeruginosa is isolated most often from the blood of bacteremic patients with typhlitis, there is some evidence that Clostridium septicum might be the primary gastrointestinal pathogen. The presentation is usually acute, with sudden onset of fever, abdominal pain, and distension which increase gradually. Localized disease can be surgically excised. Widespread involvement of the GI tract usually is fatal. Perirectal infections are common and serious infections occur most often in severely neutropenic, leukemic patients. P. aeruginosa is among the most common isolates, from both the perirectal sight and from the blood of patients who have an associated bacteremia. These infections are frequently the source of hematogenous dissemination, and several studies have reported bacteremia rates of > 50% (40). Patients with bacteremia have a higher mortality. Surgical incision and drainage seem to improve

Respiratory Tract

Pseudomonas uerugima is the most commonly isolated gram-negativeorganism from patients with microbiologically proven nosocomial pneumonia. 'Ihe infection is generally hospital acquired and is most likely to occur in patients with hematologicmalignancies and cystic fibrosis. However, cases of "community-acquired" pseudomonas pneumonia are being described in cancer patients who are not hospitalized but are receiving treatment in outpatient clinics. The signs and symptoms include confusion, apprehension, toxic appearance, chills, fever, cough, dyspnea, and relative bradycardia (43). The typical radiographic pattern is that of a diffuse and often bilateral, bronchopneumonia. Therapy is suboptimal, probably because of the poor penetration of most antibiotics into bronchial secretions, and mortality often exceeds 50-70%. The use of "aerosolized" or endotracheally administered antibiotics in conjunction with systemically administered antibiotics might increase drug levels in bronchial secretions and improve the overall outcome.

The majority of urinary tract infections caused by P. aenrginosa in cancer patients are acquired during hospitalization and occur after insertion of urinary catheters, following prolonged antibiotic treatment of other infections, or after genitourinary manipulation. Response to appropriateantimicrobial therapy is generally excellent. Other sites of pseudomonas infection which are not particularly common in patients with cancer include the heart, bones and joints, brain and spinal cord, and burn wounds. Blood The largest and most recent experienceof P. aeruginosu bacteremia in cancer patients reviewed 410 episodes that occurred over a 10-year period (44). The overall rate of Pseudomom bacteremia was 4.7 cases per lo00 admissions. The majority of patients (58 %) who developed this infection had hematologic malignancies, most commonly acute leukemia. Neutropenia was the most important predisposing factor, with 69% having an initial neutrophil count of < 1000/mm3and 40% being severely


Pseudomom aeruginosa in Cancer Patienis neutropenicwith counts of c 100/mm3.The status of the underlying malignancy was of importance, with only 8% of patients being in partial or complete remission, whereas 73 % had recently failed or appeared to be failing therapy for their malignant disease. During the two weeks prior to the onset of Pseudomom bacteremia, 74%of patients had received cancer chemotherapy, 6 % had undergone surgical procedures, 2 % had received radiotherapy, and 4 % had received both radiotherapy and chemotherapy. The patients had spent an average of 12 days in hospital before developing their episode of bacteremia. During the 7 days preceding the onset of bacteremia, 5 1 % of patients had received antibiotic therapy for other presumed or proven infections. Fever occurred in 94% of patients and was the most common sign associated with the onset of Pseudomonas bacteremia. Fever occuITBd on the day of the first positive blood culture in 60% of patients, and preceded the first positive culture by one day in 21 % of patients. Thus only a few patients were febrile for more than 24 hours before a specific diagnosis of P. aemginosa bacteremia was made. A total of 134 patients (33 %) developed shock as a manifestation of their infection; ecthyma gangrenosum was observed in only 9 patients, and there was evidence of disseminated intravascular coagulation in only 2 patients. In most patients (53 %) P. aerugimsa grew from only one blood specimen. Only 8% of patients had more than two days of positive blood cultures, and the organisms were isolated from more than four specimens in only 5 % of patients. Other important sites of infection included pneumonia (13 1 patients), soft-tissue infection (86 patients), urinary tract infection (62 patients), ompharynx (21 patients), perirectal infection (13 patients), stool (9 patients), and intravenous catheter (5 patients). The overall cure rate was 62 %; it was 67%for patients receiving appropriate antibiotics,but only 14%for those receiving inappropriate therapy. A one- to two-day delay in the administration of appropriate antibiotic therapy reduced the cure rate from 74% to 46%. Patients with shock, pneumonia, or persistent neutropenia had a substantially poorer prognosis. Several other reviews of pseudomonas bacteremia in patients with cancer have been published. Investigators from the Baltimore Cancer Research Center published their experience between 1970 and 1972, during which period, P. aenrginosa caused 28% of all cases of bacteremia at that center (45). The rate of pseudomonas bacteremia was highest in patients with acute leukemia (36%),followed by patients with lymphoma (28%),and

49

only 13%in patients with solid tumors. Among patients colonized with P. aerugimsa, the major predisposingfactor to bacteremia was neutropenia; no patient with a neutrophil count of > 1000/mrn3 became bacteremic, whereas 44% of patients with neutropenia developed bacteremia. Investigators at Memorial Sloan-Kettering Cancer Center (New York) reported on their experience with 50 episodes of pseudomonas bacteremia in cancer patients during 1967-1968 and 52 episodes during 1971-1972 (46,47). The majority of patients had either acute leukemia (35 patients) or lymphoma (30 patients). Ninety-two of the 102 infections were hospital acquired. Mortality was 78% in the earlier series and 69% in the later series. Again, neutropenia and the prbmpt administration of appropriate antibiotics were identified as important prognostic factors. Only 15 % of the 39 patients with < 1 ,OOO blood cells/mm3survived compared with 22 % of 37 patients with 1,OOO-1O,OOO white blood cells/mm3and 50% of 26 patients with > 10,ooOwhite blood ceUs/mm3.Also, 33 % of patients who received appropriate antibiotics survived, compared with only 5 % of those who did not. Fatality rates from pseudomonas bacteremia like that associated with other types of gram-negative bacteremias are related to the types of underlying disease (48). Patients with serious underlying diseases have a much higher mortality rate than those without serious underlying diseases. In a recently published univariate and multivariate analysis of factors influencing the prognosis of P. aemginosa bacteremia, four variables were found to independently influence outcome (49). These were development of septic shock, a neutrophil count of 95% of animals. The survival of animals given daily granulocyte transfusions depended upon the dose of cells transfused and the collection technique. In a model of pneumonia in leukopenic dogs, daily granulocyte transfusions (minimum of 5 X 1 P cells per day) and therapy with gentamicin (5 mg/kg/day) were superior to treatment with gentamicin alone, carbenicillin alone (500 mg/kg/day), both antibiotics at the same doses, or no antibiotics or granulocytes (56). In a recent experiment, the effect of piroxicam, a nonsteroidal anti-inflammatory agent, in a mouse model of P. aeruginosu pneumonia was studied (57). Treatment with piroxicam decreased leukocyte migration to, and perivascufar and peribronchial infiltration, in the lungs. It also protected animals in a dose-dependent manner, from challenge with lethal doses of P. aeruginosa. The effect of piroxicam was not related to any direct action of the drug on the organisms, but probably was related to a reduction in the inflammatory response and tissue damage inflicted by migrating phagocytes. In summary, the following general principles can be derived from the experience gained with experimental pseudomonal infections. In neutropenic animals, the early institution of antibiotic therapy is critical for survival.


Pseudomnus aeruginosa in Cancer Patients

Survival rates appear higher when combinationsof a beta lactam antibiotic and an aminoglycoside are employed rather than either drug alone. This effect may be due to antibiotic synergy, but its benefit is lost if therapy is delayed. The data, however, are conflicting and high doses of single beta lactam antibiotics have been shown to produce results similar to beta lactam, aminoglycoside combinations. Therapy with a single drug (particularly newer drugs such as the quinolones with good tissue penetration) might be effective, but might also lead to the development of drug resistance. Granulocytetransfusions are helpful if they are administenxialong with appropriate antibiotic therapy and if adequate numben of granulocytes are transfused. Monoclonal antibodies, in combination with appropriate therapy, may improve survival, and nonsteroidal anti-inflammatory agents might be helpful in specific infections such as pneumonia.

ANTIMICROBIAL THERAPY The first agents introduced into clinical practice that were active against P. aeruginosu were polymixin B and colistin. Unfortunately, their clinical efficacy did not match their in vitro activity and the polymixins were found to be of little benefit in the treatment of pseudomonas bacteremia in patients with cancer. Subsequently, several classes of antibiotics have become available for clinical use that are active against P. ueruginosa. These include the aminoglycosides, the antipseudomonalpenicillins, the extended spectrum cephalosporins, newer beta lactam structures such as the monobactams (aztreonam) and carbapenems (imipenem), and the newer 4-quinolones. Gentamicin was the first aminoglycosidewith good activity against P. aeruginosu. When it was first introduced most clinical isolates were inhibited by concentrationsof In an early study a cure rate of only 29% ~ 4 . pg/ml. 0 among 21 patients with pseudomonas bacteremia was reported (62). Cure of the infection with irradiation of the bacteremia depended upon peak serum levels of gentamicin. However, even adequate peak serum levels were not effective in patients with “rapidly fatal” underlying disease. Another study demonstrated m patients with cancer that the cure rate with gentamicin inversely correlated to the neutrophil count at the onset of gramnegative bacillary infections, being 79 % among patients with an initial neutrophil count of > 1000/mm3, but only 23% among patients with severe neutropenia (< 100/mm3). Response was also related to changes in the neutrophil count during the course of the infection; the cure rate being 74% in patients whose counts increased

51

compared with 31 % in patients whose counts decreased (63). Many new aminoglycosides with substantial antipseudomonal activity have been introduced since the discovery of gentamicin. Their in vitro activities are summarized in Table 4. Of these drugs only amikacin, tobramycin, gentamicin, and to a lesser extent netiimicin, are used clinically in the United States. In most in vitro studies, tobramycin had greater activity than gentamicin against P. aeruginosa, but gentamicin-resistant isolates were also resistant to tobramycin. Most strains require higher concentrationsof amikacin for in vitro inhibition, but the use of higher doses of amikacin eliminates this disadvantage. Several prospective randomized trids have been unable to demonstrate ihe superiority of any one aminoglycoside over the others for the treatment of pseudomonas infections. Most large studies have involved neutropenic patients with cancer and the number of pseudomonas infections in each group has been too small to detect even major differences (64).The greater in vitro potency of tobramycin would be an important consideration in the treatment of infections caused by organisms marginally susceptibleto gentamicin. The activity of amikacin against many P. aenrginosu isolates that are resistant to other aminoglycosidesis also of importance. In one recent study in a general hospital population, of 160 P. aeruginosa isolates from various clinical sources, 1.2%were resistant to amikacin, 18.1% to gentamicin, and 16.9% to tobramycin (65). Most gentamicin- and tobramycinresistant organisms were susceptible to amikacin. During a 3.5 year period of almost exclusive usage of amikacin, Table 4

In Vitro Activity of Aminoglycosides Against Pseudomonas aeruginosa No. of isolates Drug Gentamicin Tobramycin Amikacin Sisomicin Netilmicin Dibekacin Fosfomycin

tested

MIC5Oa

MICW

150

4.0 0.25 4.0 4.0 4.0 2.0

32.0 8.0

150 200 100 100

247 71

12.5

16.0

32.0 32.0 4.0 100.0

aThe MICSO and MICW are the lowest Concentrations in p g / d of each agent required to inhibit the growth of 50%and 9096,respectively of all strains tested. Source: Data are from Refs. 58-61.

Rolston and Bodey


52

a fall of overall resistance to gentamicin and tobramycin was noticed without an increase in amikacin resistance. Resistance to aminoglycosides is most often due to enzymatic modification of the drugs by acetylation, adenylation, or phosphorylation. These enzymes can be transmitted to other organisms via plasmids. Most enzymes that inactivate gentamicin also inactivate tobramycin, thus, cross-resistanceusually occurs between these two agents. Because amikacinis effectively d e d by only one enzyme found in P. ueruginosa, many isolates resistant to other aminoglycosides are susceptible to amikacin. Hence amikacin should be routinely used in those incidents where gentamicin resistance is common. Several properties of aminoglycosideshave limited their usefulness as single agents for the treatment of pseudomonas infections. Resistance has emerged as a problem in several institutions. Penetration into some tissues is poor. For instance, minimal concentrations are detected in sputum, which might explain the marginal efficacy of these agents in the treatment of pseudomonas pneumonia. Also, pus inactivatesaminoglycosides in vitro, therefore, drainage remains important in the management of abscesses. Finally, the potential for ototoxicity and nephrotoxicity limit their usefulness in many patients including the elderly, and cancer patients who must be treated with other toxic agents such as cis-platinum or amphotericin B. The discovery of carbenicillin, a penicillin with antipseudomonal activity provided an impetus for the synthesis of many new penicillins, and, subsequentlycephaIosporins and other beta lactam antibiotics. Their in vitro activity against P. aentginosa is summarized in Table 5 . The availability of carbenicillin for the therapy of infections caused by P. ueruginosu had a major impact on the outcome of these infections. In a study of 59 pseudomonas infections in patients with cancer, the response rate to carbenicillinwas 75 % overall and 71% in septicemic patients (69). The cure rate was independent of the patients’ neutrophil count and was similar whether the patients’ counts increased or decreased during infection (82 vs. 76%). Subsequently, pseudomonas infections in an additional 53 patients with cancer were treated with combination antibiotic regimens in which carbenicillin was the only antipseudomonalagent; infection was cured in 80% of these patients (70). In a collated series of 114 pseudomonas infections, 94 (82%) responded to carbenicillin (7 1). The response in 25 septicemic patients was 85 % . Although some patients also received gentamicin, usually their infection had failed to respond to it before the addition of carbenicillin. Initial studies with carbenicillin provided somewhat conflicting

Table 5 In Vitro Activity of B-Lactam Antibiotics Against Pseudomonas aeruginosa No. of isolates tested

Drug Carbenicillin

2256

Ticarcillin

2034

MICW

MICW

64.0 32 .O

256.0 28.0

+

Ticarcillin clavulanic acid

1385

16.0

128.0

Azlocillin

1130

16.0

64.0

Mezlocillin

1380

64.0

128.0

Piperacillin

1208

8.0

64.0

Cefotaxime

1542

32.0

64.0

1417

8.0

32.0

168

8.0

32.0

Moxalactam

776

32.0

64.0

Ceftazidime

574

2.0

32.0

Cefoperazone Cefoperazone sulbactam

+

Cefsulodin

965

4.0

16.0

Cefmenoxime

258

16.0

64.0

Cefpirome

200

2 .o

32.0

Aztreonam

361

4.0

32.0

Imipenem

392

2 .o

8.0

aMIC50 and MICW are the lowest concentrations in p g / d of drug, required to inhibit 50% and 9096,respectively, of isolates tested. Source: Data are from Refs. 58-61, 66-68.

data regarding its efficacy because some investigators utilized marginal doses. Also, the relatively short halflife of carbenicillin required frequent dosing particularly in neutropenic patients. Shortly after its introduction into clinical practice reports of rapidly emerging resistance among P. aeruginosa isolates from patients being treated with carbenicillin began to appear. This resistance was due to a penicillinase that was transferable in vitro to other strains of P. aeruginosa and Enterobacteriaceae.In most cases the MIC increased by about fourfold, but the increase did not generally result in failure of therapy. Also, the resistant isolate often disappeared upon discontinuation of carbenicillin. Some reports of the emergence of resistance were exaggerated due to a lack of standardization in the procedures used for reporting resistance to carbenicillin. The development of ticarcillin provided an antipseudomonal agent twice as active as carbenicillin (Table 5 ) .


Pseudomom aeruginosa in Cancer Patients

However, most strains that were resistant to carbenicillin were also resistant to ticarcillin. Ticarcillin has been used extensively for the treatment of pseudomonas infections generally in combination with an aminoglycoside. Therefore, large-scale studies evaluating the efficacy of ticarcillin alone have not been published. Ticarcillin cured 84 % of a series of 43 pseudomonas infections in patients with cancer, inchding 7 of 11 episodes of septicemia (70). Similar data were reported from patients without cancer. Ticarcillin replaced carbenicillinas the antipseudomonal penicillin of choice in many institutionsbecause it can be administered at a lower dosage and probably causes less frequent and less severe hypokalemia and hyponatremia. The newer antipseudomonal penicillins mezlocillin, azlocillin, and piperacillin, all of which became available in the early 1980s are at least as active (mezlocillin) or more active (azlocillin,piperacillin)thancarbenicillin and ticarcillin against P. aemginosa (Table 5). Some of the extended spectrum cephalosporins are also quite active against P. aeruginosa. Among these agents ceftazidime has the greatest in vitro antipseudomonal activity, but moxalactam (an agent whose usage has declined) and cefoperazone also have substantial activity. Cefsulodin is an interesting analog because its activity against gramnegative bacilli is limited to P . aeruginosa. In addition, newer beta lactam structures such as the monobactam aztreonam, and the mbapenem imipenem, have been shown to have impressive in vitro antipseudomonal activity. Several of the new beta lactam antibiotics have been intrduced into clinical practice, but experiencewith them as antipseudomonalagents is somethat limited. This is due primarily to the fact that it has become very uncommon in recent years to accumulatelarge numbers of pseudomoMS infections. For example in a large trial of three different antibiotic regimens conducted by the EORTC, a total of 1074 febrile episodes were studied and only 34 infections were caused by P. aeruginosa (72). Hence a maximum of 13 cases of pseudomonas infection were treated with any one antibiotic regimen. This small number makes it difficult to draw definite conclusions regarding the relative efficacy of different regimens. The decline in the frequency of pseudomonasinfections is due to changes in therapeutic practices and improvement in antipseudomonal therapy. At our institution, P. aeruginosu caused 49% of all episodes of gram-negative bacillary septicemia during 1966-1968 (prior to the availability of carbenicillin) but only 18% of episodes during 1969-1972 (after wbenicillin was used routinely) and 20% of episodes in 1987 (73,74). Several studies have been conducted at our institution using some of the newer beta-lactam agents as mono-

53

therapy for gram-negative infections. Vancomycin was used in some regimens to provide coverage against grampositive pathogens. The limitations of these data are that not all patients treated with these antibiotics were neutropenic; the nature of infections seen was different with more complicated infections being treated by some agents and simple infections by others; the usage of antibiotics was different with some agents being given as initial therapy and others as secondary therapy, after failure of an initial regimen. Again the numbers of pseudomonas infections treated with each agent is very small (data summarized in Table 6) and no definite conclusions regarding their therapeutic efficacy can be made. A major advance in antimicrobial therapy in the past few years has been the development of the newer fluoroquinolones. Although these agents have been available in the United Staes for less than 4 years, there has been extensive use of the two commercially available agents, norfloxacin and ciprofloxacin. Several other fluoroquinolones are at various stages of development. The activity of these agents against P. aeruginosa is summarized in Table 7. Among the agents that are currently available or are near release by the FDA, ciprofloxacin has the greatest in vitro activity against these organisms. Norfloxacin has been used primarily to treat urinary tract infections. Both norfloxacin and ciprofloxacinhave been used for infection prophylaxis in leukemic patients (87,88). Ciprofloxacin has been evaluatedboth as a single agent and in combination with other antibiotics for the therapy of infections in cancer patients. These data are preliminary and the number of patients treated is small. However, 8 of 10 patients treated at our institution for P. aeruginosa infections responded to therapy with ciprofloxacin (89,90). Table 6 Therapeutic Results with Newer Beta-Lactam Antibiotics in Cancer Patients Treated at the M. D. Anderson Cancer Center Antibiotic Cefazidime Ticarcillim clavulanic acida Aztreonamb Imipenemb

+

No. of episodes

% Response

15

100

9

89

7 20

57 55

*Not all patients receiving ceftazidime or ticarcillin + cladanic acid were neutropenic. bMost infectiom were complicated (pneumonias) or had failed other therapeutic regimens. Source: Data are from Refs. 74-80.

Rolston and Bodey

54

Table 7 In Vitro Activity of Newer CQuinolone Against Pseudomonas aeruginosa Drug

No. of isolates tested

MIC5Oa

MICW

40

1 .o

8.0

Amifloxacin

40

1 .o

2.0

150

0.12

0.5

CI-934

50

2.0

8.0

Difloxacin

50

2.0

8.0

Enoxacin

2.0

4.0

Fleroxacin

90 40

1 .o

4.0

Ofloxacin

120

0.5

4.0

Pefloxacin

35

1 .o

8.0

PD117, 558

100

0.5

4.0

PD117, 596

100

0.06

0.12

PD127, 391

100

0.12

0.12

A-56620


Ciprofloxacin

Sparfloxacin

50

1 .o

2.0

S-29530

40

4.0

16.0

S-29532

40

8.0

32.0

100

0.5

Temafloxacin ~~

~

~~

4.0 ~~

aMIC50 and MIC90 are the lowest concentrations in pg/ml required 90%. respectively, of isolates tested. Source: Data are from Refs. 81-86. to inhibit 50% and

The potential for emergence of resistant organisms during therapy with the newer beta lactams and fluoroquinolines has been of some concern. For example, in a survey of antibiotic susceptibilityamong gram-negative bacilli done at our institution, the incidence of resistance to P. aeruginosa isolates increased from'9% to 20% for aztreonam, 7 % to 13% for cefoperazone, 4 % to 6 % for piperacillin and 0.6 % to 7 % for imipenem during a study period which began in December 1985 and ended in November 1986 (91). No increase in resistance was observed with cipmfloxacin. However, ciprofloxacin had not been used at all in this institution, whereas the other antimicrobial agents tested had been used extensively. Reports of ciprofloxacin resistant P. aeruginosa isolates have appeared from other institutions (92). These data are of some concern since they suggest that antimicrobial resistance is a potential problem particularly in patients with neutropenia or cystic fibrosis in whom heavy antibiotic usage is often unavoidable.

The generally accepted practice for the treatment of serious pseudomonas infections has been to use a combination of an antipseudomonal penicillin and an aminoglycoside. This practice is based on in vitro and animal data which suggest that these agents interact in a synergistic manner. Antipseudomonalpenicillins act synergistically with aminoglycosidesagainst approximately 30-50% of P. aeruginosa isolates. There have been some clinical reports indicating that synergistic antibiotic combinations are more effective than nonsynergistic ones (93,94). Closer scrutiny of these results indicates the differences probably were due to the difference in efficacy between antipseudomonalpenicillins, and aminoglycosides, in patients with neutropenia. The only type of synergistic combination included in the studies reviewed was an aminoglycosideplus a penicillin. Nonsynergistic combinations generally included an aminoglycoside plus an antibiotic without antipseudomonalactivity, such as a cephalosporin. Hence, the real comparison was that of an aminoglycosidealone versus a combinationcontaining an antipseudomonalpenicillin. Since it has been conclusively demonstratedthat aminoglycosidesby themselves are not adequate for the treatment of gram-negative infections in neutropenic patients, it is not surprising that the aminoglycoside, antipseudomonal penicillin combinations appeared superior. Serum bactericidal activity might be of greater significancein the management of gram-negative bacillary infections, both in neutropenic and nonneutropenic patients, than the potential for synergisticinteraction. In one study peak serum bactericidal titers of 1:8 or more and 1:16 or more were found to correlate with a statistically significant favorableoutcome of gram-negativebacillary bacteremia (including P. aeruginosa bacteremia) in nonneutropenic and neutropenic patients, respectively (52). This might explain the results of several recent studies in which single agents with good bactericidal activity such as cefoperazone, ceftazidime, aztreonam, and imipenem, have produced response rates in neutropenic cancer patients that compare favorably to response rates produced by combinations that are potentially synergistic (78,79,95,96). Another reason for using the combination of an antipseudomonal penicillin and an aminoglycoside is that it may reduce the likelihood of the emergence of resistant P. aeruginosa. In studies where this was examined such a combination did not prevent colonization with penicillinresistant organisms (97). The availability of extended spectrum cephalosporins (and other beta-lactam structures) requires critical reappraisal of this question. Several recent studies have demonstrated that the combination of



55

an antipseudomonalpenicillin and an extended spectrum

IMMUNOLOGIC APPROACHES

cephalosporin with antipseudomonas activity is as effective as the combination of either of these drugs with an aminoglycoside (89-100). However, in most of these studies too few pseudomonas infectionswere included to make a meaningfid appraisal of this approach, specifically for infections caused by P. ueruginosu. By using these “double beta-lactam” combinationsit is possible to avoid the risk of nephrotoxicity and ototoxicity from aminoglycosides-an important considerationfor patients with impaired renal function and for cancer patients receiving other nephrotoxic drugs (cis-platinum, amphotericin B) . In most of the studies employing a combination of a penicillin and a cephalosporin, the incidence of the development of resistant organisms was not greater than that with penicillin-aminoglycoside combinations. The availability of antimicrobial agents with antipseudomonas activity has had a profound impact on the treatment of pseudomonas infections. Several problems, however, still =main. First, different investigators use different criteria for failure of antimicrobial regimens. Since serious pseudomonas infections occur primarily in patients with serious underlying disease, some patients die of causes other than infection. Often this fact is not taken into account and death is ascribed to failure of the antibiotic@)to eradicate the infection. Uniform criteria for assessing the efficacy of antibiotic therapy are needed in order for meaningful comparisonsof data from different institutionsto be made. Second, the population of patients developing pseudomonas infections is changing. More intensive antineoplastic regimens are being used for the treatment of cancer, bone marrow transplants are being performed more frequently and for a wider spectrum of indications, and prosthetic devices and central venous catheters are being used more extensively than in the past. These and other factors influence the outcome of pseudomonas infection independent of the nature of antimicrobial therapy. Removal of an infected central venous catheter, for instance, is essential for recovery from catheter-relatedP. ueruginosu bacteremia (101). Third, and most important is the timing of antimicrobialtherapy. In high-risk patients empiric antipseudomonal therapy should be administered at the onset of infection, not after a specific diagnosis has been established. Mortality in the first 24 hours approaches 35% if appropriate therapy is not instituted immediately. Those studies showing major improvement in the results of treatment were conducted in closely controlled units where antipseudomonaltherapy was administered at the onset of fever, not after the establishment of the diagnosis.

A number of investigators have sought methods for overcoming the defects in host defense that contribute to the increased incidence of infections in patients with cancer. The most important components of host defense against pseudomonas infection include phagocytic cells and antibodies. In order to augment these host defenses, a number of approacheshave been tried. Cell component replacement with granulocyte transfusiontherapy has been successfulin a dog model of neutropenia associated with pseudomonas pneumonia. Human data are not as promising and the variable successes reported in various trials appear to be related to the difficulty in obtaining viable white blood cells in sufficient numbers and avoiding the transmission of viral infections (102). Another approach is the use of vaccines for P. ueruginosu. The development of antipseudomonasvaccines for use in humans was triggered by observations of the protective role of antibody to P.aeruginosu in animals. Since pseudomonas infections are a serious problem in patients with cancer, determination of the efficacy of vaccines in this population was of great importance. In one large study 176 patients with leukemia and solid tumors were vaccinated and the outcome of their infection was compared with that in 185 control patients (103). Fatal pseudomonas septicemia occurred in 19 controls and 10 patients who had been vaccinated. Mortality associated with pseudomonas infection was 7 % for the vaccinated group compared with 17%for the control group. These results indicate limited efficacy of the vaccine. Unfortunately, there was an unacceptably high incidence of both localized and systemic adverse reactions. Two other studies in patients with leukemia have demonstrated some benefit of pseudomonas vaccines (104,105). Modem technology in the sphere of biomedical research has enabled investigators to produce substances of high purity and specificity against concerned regions of gramnegative polysaccharide (endotoxin). These monoclonal antibodies have been evaluated both in animal model studies and in early human trials. IgG and IgM antibodies to the 0 antigens of most of the common serotypes of P. aeruginosu have been produced, and these antibodies are highly protective in experimental models of infection (106). Early clinicaltrials of an IgM monoclonal antibody designated E5 antibody in patients with gram-negative bacteremia who were also receiving appropriate antimicrobial therapy were promising (107). Based on this trial a randomized, prospective, double-blind trial of E5 is underway, and any judgments about therapeutic efficacy

Rolston and Bodey

56

of E5 will have to be made after the results of this trial become available (108). The development of purified recombinant granulocytemacrophage-colony-stimulating factor (GM-CSF) offers the possibility of reducing the period of risk for serious infections including those caused by P. aeruginosa by shortening the duration of neutropenia (109). Clinical trials are underway in order to examine the efficacy of this approach.


SUMMARY Pseudomonus aeruginosa is an important cause of infection in immunosuppressedpatients, particularly those with cancer. However, it is being recognized with greater frequency in patients who appear to be immunwmpetent. Changes in modem lifestyles have led to the appearance of some new manifestations of pseudomonas infection including corneal ulceration and keratitis associated with contact lenses, and hot-tub- or whirlpool-associated folliculitis. These represent additional hazards to patients with cancer. Many studies, both in animals and humans, have contributed to our knowledge of the pathogenesis, immunology, treatment, and prevention of pseudomonas infections. Although the aminoglycosides represented a significant step forward in the treatment of these infections, of greater importance was the discovery of the antipseudomonal penicillins. These antibiotics are more effective than the aminoglycosides in neutropenicpatients, who are especially susceptibleto pseudomonal infections. The older antipseudomonal penicillins (carbenicillin, tircarcillin) have largely been replaced by newer ones (mezlocillin, azlocillin, pipercillin) which are more potent in vitro against P. aeruginosa. Athough the accepted therapeutic practice has been to utilize a penicillin in combination with an aminoglycoside, the introduction of newer beta lactam agents and flwroquinoloneswith antipseudomonal properties offers the possibility of other approaches to combination therapy. These include the combination of a penicillin or a cephalosporin or the combination of a quinolone with an aminoglycosideor a betalactam antibiotic. However, the development of newer antimicrobial agents is not likely to be a lasting solution to the problem of pseudomonas infections. Since pseudomonas infection often progresses rapidly, optimal results will always depend upon the prompt initiation of appropriatetherapy in febrile patients, particularly those who are at high risk. The use of granulocyte transfusions has proved to be of limited benefit. Early data with the use of monoclonal antibodies is promising, and the results

of large-scale trials are eagerly awaited. It is hoped that continuing investigation of pseudomonas vaccines will lead to the discovery of effective prophylaxis for highly susceptible patients. It is also hoped that with the availability of GM-CSF it will become possible to reduce the period of risk for serious infections. Finally, a reduction in the freqwcy of microbiologically proven P. uemginosa infections in cancer patients should not lead to the assumption that these organisms do not constitute a problem in such patients anymore. The use of prophylactic antibiotics and prompt empiric antibiotic coverage for therapy has resulted in this decline. Cultures are therefore unlikely to be positive with the same frequency as they were before antimicrobialprophylaxis and empiric antibiotic therapy became standard practice. However, some febrile episodes in neutropenic patients that are microbiologically undocumented are probably the result of infection with P. aemginosa and empiric therapy should always include antipseudomonal agents.

REFERENCES 1. Cross A, Allen JR, Burke J et al: Nosocomial infections due to Pseudomom aeruginara: review of recent trends. Rev Infect Dis ~ ( S U P 5):S837-S845, P~ 1983. 2. Favero MS, Carson LA, Bond WW, Petersen NJ: Pseudomonas aeruginosa. Growth in distilled water from hospitals. Science 173:836-837, 1971. 3. Kominos SD, Copeland CE, Grosiak B, Postic B: Introduction of Pseudomonas aeruginosa into a hospital via vegetables. Appl Microbiol 24:567-570, 1972. 4. Schimpff SC, Moody M, Young VM: Relationship of colonization with Pseudomnas aeruginosa to developmentof pseudomonas bacteremia in cancer patients. Antimicrob Agents Chemother: 240-244, 1970. 5. Bodey GP: Epidemiological studies of pseudomonas species in patients with leukemia. Am J Med Sci 260:82-89, 1970. 6. Whitecar JP Jr, LUMM, Bodey GP: Pseudomonas bacteremia in patients with malignad diseases. Am J Med Sci 260:216-223, 1970. 7. Peterson PK: Host defense against Pselcdomom aeruginosa. In Pseudomonas aeruginom. International Symposium. Edited by LD Sabbath, Hans Huber Publisher, Bern, 1980, pp 103-118. 8. Pollack M: Pseudomoms aeruginosa exotoxin A. N Engl J Med 302:1360-1362, 1980. 9. Iglewski BH, Kabat D: NADdependent inhibition of protein synthesis by PseudanoMs aeruginosa toxin. Proc Natl Acad Sci (USA) 72:2284-2288, 1975. 10. Atik M, Liu PV, Hanson BA, Amini S, Rosenberg CF: Pseudomonas endotoxin shock: a preliminary report of studies in dogs. J Am Med ASSN 205~134-140, 1968. 11. Pavlovskis OR, Callahan LT III, Pollack M: Pseudomonas aeruginosa exdoxin. In Microbiology. Edited by D Schlessinger. American Society for Microbiology, Washington, DC, 1976, pp 252-256.


Pseudomoms aeruginosa in Cancer Patients 12. Cross AS, Sadoff JC, Iglewski BH, Sokol PA: Evidence for role of toxin A in the pathogenesis of infection with Pseudomonas aeruginosa in humans. J Infect Dis 142:535-546, 1980. 13. Pollack M, Young LS:Protective activity ofantibodies to exotoxin A and lipopolysaccharideat the onset of PsardomoMs aeruginosa septicemia in man. J Clin Invest 63:276-286, 1979. 14. Liu PV: Toxins of Pseudomonas aeruginosa. In Pseudomonas aeruginosa: Clinical Manifestaiions of Infection and Current 7Wap.y. Edited by RG Dogget. Academic Press, New York, 1979, pp 63-88. 15. Berka RM, Gray GL, Vasil ML: Studies of phospholipase (heatlabile hemolysin) in Pseudomonas aeruginosa. Infect Immun 34~1071-1074, 1981. 16. Tillotson JR, Lerner AM: Characteristics of non-bacteremic Pseudomonas pneumonia. Ann Intern Med 68:295-307, 1968. 17. Woods DE, Straus DC, Johanson WG Jr, Bass JA: Role of pile in adherence of Pseuahonas aeruginosa m mammalian buccal epithelial cells. Infect Immun 29: 1146-1 151, 1980. 18. Ramphal R, Small PM, Shands JW Jr et al: Adherence of Pseudomonas aeruginow to trachael cells injured by influenza infection or by endobracheal intubation. Infect Immun 27:614-619, 1980. 19. Brown MRW, Foster JHS, Clamp J R Composition of Pseudomonas aeruginma slime. Biochem J 112521426, 1969. 20. Schwarzman S, Boring JR III: Antiphagocyticeffect of slime from a mucoid strain of PseudomoMs aeruginosa. Infect Immun 3~762-767, 1971. 21. Sensakovic JW, Bartell PF: The s l h of Pseudomoms aemginosa: biological characterization and possible role in experimental infection. J Infed Dis 129:lOl-109, 1974. 22. Young LS, Armstrong D: Human immunity to Pseudomonas aeruginosa. In vitro interaction of bacteria, polymorphonuclear leucocyte and serum factors. J Infect Dis 126:257-276, 1972. 23. Reynolds MY: Pulmonary host defenses in rabbits after immunization with pseudomonas antigens: the interaction of bacteria, antibodies, macrophages and lymphocytes. J Infect Dis 130 (S~ppl):S134-S142, 1974. 24. Pollack M, Anderson SE Jr: Toxicity of Pseuainnonas aeruginosa exotoxin A for human IIpLcToph88es. Infect Innnun 19:1092,10-%, 1978. 25. Chester IR, Meadow PM, Pin TL: The relationship between the &antigenic lippolysaccharides and serological specificity in strains of Pseudomoms aeruginosa of different 0-serotypes. J Gen Microbiol 78:305-318, 1973. 26. Peterson PK, Kim Y, Schmeling D, Lindemann M, Verhoef J, Onie PG: Complement mediated phagocytosis of Pseudomonas aeruginosa. J Lab Clin Mcd 99:883-894, 1978. 27. Bjornson AB, Michael JG: Factors in human serum promoting phagocytosis of Pseudomonas aeruginosa. 1. Interaction of opsonins with the bacterium. J Infect Dis 13O(Suppl):5119-5126, 1974. 28. Southam CM, Pillemer L: Serum properdin levels and cancer cell homografts in man. Proc SOCExp Biol Med %:596-601, 1957. 29. Dorff GJ, Geimer NF, Rosenthal DR et al: Pseudomonas septicemia: illustrated evolution of its skin lesions. Arch Intern Med 128:591-595, 1971. 30. Huminer D, Siegmen-Igra Y, MorduchowiczG, Pitlik S: Ecthyma gangrenosum without bacteremia: report of six cases and review of the literature. Arch Intern Med 147:299-301, 1987. 31. Kusne S, Eibling DE, Yu VL et al: Gangrenous cellulitis associated with gram-negativebacilli in pancytopenicpatients. Dilemma with

57 respect to effective therapy. Am J Med 85:490-494, 1988. 32. Fainstein V, Andres A, Umphrey J, Hopfer RL: Hair clipping: another hazard for granulocytopenic patients. J Infect Dis 158:655-656, 1988. 33. Rosenoff SH, Wolf ML, Ghabner BA: Pseudomow blepharoconjunctivitis. A complication of combination chemotherapy. Arch Ophthalmol91:490-4491, 1974. 34. Salit IE, Miller B, Wigmore W, Smith JA: Bacteria flora of the external canal in diabetics and mn-diabetics. Laryngoscope 92:672-673, 1982. 35. Sobie S, Brodsky L, Stanievich JF: Necrotizing external otitis in children: a report of two cases and review of the literature. Laryngoscope 97598601, 1987. 36. Rubin J, Yu VL: Malignant external otitis: insights into pathogenesis, clincial manifestations, diagnosis and therapy. Am J Med 85:391-398, 1988. 37. Chandler JR: Malignant external otitis and facial paralysis. Otolaryngol Clin North Am 7:375-383, 1979. 38. Caplan ES, Hoyt HJ: Nosocomial sinusitis. J Am Med Assoc 247~639-641, 1982. 39. Wagner ML, Rosenberg MS,, Fernbach DJ, Singleton EB: Typhlitis: A complication of leukemia in childhood. Am J Roentgen, Radio1 Ther Nucl Med 109:341-350, 1970. 40. Schimpf SC, Wiernik PM, Block J B Rectal abscess in cancer patients. Lancet 2844-847, 1972. 41. Rolston K. Paulino A, Elting L et al: Perirectal infections in cancer patients. Proc Intersci Conf Antimimob Agents Chemother, New York, 1987 (Abstr #966). 42. Barnes SG,Sanler FR, Ballard JO: Perirectal infections in acute leukemia. Improved survival after incision and debridement. AM Intern Med 100:515-518, 1984. 43. Tillotson JR, Lerner AM: Characteristics of nonbacteremic pseudomonas pneumonia. Ann Inter Med 68:295-307, 1968. 44. Bodey GP, Jadeja L, Elting L: Pseudomonas bacteremia: Retrospective analysis of410Episodes. Arch InterMed 145:1621-1629, 1985. 45. Schimpff SC, Greene WM, Young VM,Wiernik PM: Significance of Pseudomom aeruginosa in the patient with leukemia or lymphoma. J Infect Dis 13O(Suppl):5524-5531, 1974. 46. Fishman LS, Armstrong D: Pseudomonas aeruginosa bacteremia in patients with neoplastic disease. Cancer 30:764-773, 1972. 47. Tapper ML, Annstrong D: Bacteremia due to Pseudomonas aeruginosa complicating neoplastic disease. A progress report. J Infect Dis 130(Suppl):514-523, 1974. 48. Bryant RE, Hood AF, Hood CE, Koenig MG: Factors affecting mortality of gram-negative rod bacteremia. Arch Intern Med 127:120-128, 1971. 49. Bisbe J, Gatell JM, Puig J et al: Pseudomonas aeruginosa bacteremia. Univariate and multivariate analysis of factors influencing the prognosis of 133 episodes. Rev Infect Dis 10:629-635, 1988. 50. M o l e VT: Synergy ofcarbenicillinand gertamicin in experimental infections with pseudomonas. J Infect Dis 124(Suppl):546-555, 1971. 51. Andriole VT: Antibiotic synergy in experimental infection with Pseudomonas II. The effect of carbenicillin, cephalothin, or cephanone combined with tobramycin or gentamicin. J Infect Dis 129~124-133, 1974. 52. Sculier JP, Klsstersky J: Significame of serum bactericidal activity in gram-negative bacillary bacteremia in patients with and without granulocytopenia. Am J Med 76:429-435, 1984.

Rolston and Bodey


58 53. Hector RE, Collii MS, PenningtonJE: Treatment of experimental Pseudomow aeruginasa pneumonia with a human IgM monoclonal antibody. J Infea Dis 160:483-489, 1989. 54. Collins HH, Gross AS, Dobet A et al: Oral ciprofloxacin on a monoclonal antibody to lipopolysaccharideprotect leucopenic rats from lethal infection with Pseudomonas aemginosa. J Infect Dis 159:1073- 1082, 1989. 55. Applebaum FR, Bowles CA, Makuch RW, Deissemth AB: Granulocyte transfusion therapy of experimental pseudomonas septicemia. Study of cell dose and collection technique. Blood 52:323-331, 1978. 56. Dale DC, Reynolds HY, Pennington JE et al: Experimental pseudomom pmumonia in leuwpemc dogs: comparisonof therapy with antibioticsand granulocyte trmfusions. Blood 473369-876, 1976. 57. Sordelli DO,CerquettiMC, Fontan PA, Meiss Rp: Piroxicam treatment protects mice fiom lethal pulmonary challenge with Pseudomow aeruginasa. J Infect Dis 159232-238, 1989. 58. Rolston KVI, ChandrasekarPH, LeFrock JL, Schell RF: The activity of cefazidime, other 0-lactams, and aminoglycosidesagainst Pseudomow aeruginasa. Chemotherapy 30:31-34, 1984. 59. Chandrasekar PM, Schell RF, LeFrock JL et al: Activity of cefsulodin, other 0-lactams, and amimgiycosides against Pseudomonas aeruginasa. Chemotherapy 30:165-169, 1984. 60. Hoy JF, Rolston KVI, Ho DH et al: In vitro activity of BRL 36650, a new semisynthetic penicillin. Antimicrob Agents Chemother 29:972-976, 1986. 61. Bodey GP, Bolivar R, Fainstein V, Jadeja L: Infections caused by Pseudomonas aeruginosa. Rev Infect Dis 5279-313, 1983. 62. Jackson GG, Riff LJ: Pseudomom bacteremia: pharmacologic and other basis for failure of treatment with gentamicin. J Infect Dis 124(Suppl):5185-5191, 1974. 63. Bodey GP, Middleman E, Umsawadi T, Rodriguez V: Infections in cancer patients. Results with gentamicin sulfatetherapy. Cancer 29:1697-1701, 1972. 64. Bodey GP: Aminoglycoside use in the compromised host. In The Am'noglycosides. Edited by A Whelton and HC Neu. Marcel Dekker, New York, 1982, pp 557-583. 65. Berk SL, Alvarez S, Ortega G et al: Clinical and microbiologic consequences of &in use during a 42-month period. Arch Intern Med 146538441, 1986. 66. Rolston K, Alvarez ME, Hoy JF et al: Comparative in vitro activity of cefpimme and other antimicrobialagents against isolates from cancer patients. Chemotherapy 32:349-351, 1986. 67. Fuchs PC, Barry AL, Jones RN: In vitro activity and disc susceptibility of Timedn: current status. Am J Med 75(Suppl5B):25-32, 1985. 68. Jones RN, Barry AL, Packer RR et al: In vitro antimicrobial spectrum, occurreme of synergy, and recommendations for dilution susceptibility testing concentationsof the cefoperazone-sdbactam. J Clin Microbiol 25:1725-1729, 1987. 69. Bodey GP, Whitecar JP Jr, Middleman E, Rodriguez V: Carbenicillin therapy for pseudomonas infechns. J Am Med Assoc 218~62-66, 1971. 70. Bodey GP, Rodriguez V: The role of antipseudomonalpenicillins in the management of infections in cancer patients. In Ticarcillin (BRL2288). International Symposium. Excerpts Mtdica, Amsterdam, 1977, pp 151-157. 71. Bodey GP, Bolivar R,Fainstein V, Jadeja L: Infections caused by Pseudomonas aeruginosa. Rev Infect Dis 5279-313, 1983. 72. The EORTC International Antimicrobial Therapy Cooperative

73. 74.

75.

76.

77. 78. 79.

80.

81.

82.

83.

84.

85.

86. 87.

88.

89.

90.

91.

Group: Ceftazidine combined with a short or long course of amikacin for empirical therapy of gram-negative bacteremia in cancer patients with granulocytopenia. N Engl J Med 317: 1692-1698, 1987. Bodey GP, Rodriguez V, Chang HY, Narboni G: Fever and infection in leukemia patients. Cancer 41:1610-1622, 1978. Anaissie EJ, Fainstein V, Bodey GP et al: Randomized trial of beta-lactam regimens in febrile neutropenic cancer patients. Am J Med 84:581-589, 1988. Fainstein V, Bodey GP, Elting L et al: A randomized study of ceftazidime compared to ceftazidimeand tobramycin for the treatment of infections in cancer patients. J Antimicrob Chemother 12(S~pplA):lOl-110, 1983. Fainstein V, Eltin L, P i d i S et al: Ticarcillinplug clavulanic acid in the treatment of patients with cancer. Am J Med 79(SuppI 5B):62-66, 1985. Bodey GP, Fainstein V. Elting L et al: @-ladamregimens for the febrile neutropenic patient. Cancer 65:9-16, 1990. Jones PG, Rolston KVI, Fainstein V et al: Aztreonam therapy in neutropenic patients with cancer. Am J Med 81:243-248, 1986. Bodey GP, Alvarez M, Jones PG et al: Imipenem-cilastatinas initial therapy for febrile cancer patients. Antimicrob Agents Chemother 30211-214, 1986. Bodey GP, Rolston K, Jones P et ak Imipenedcilastatin as secondary therapy for infections in cancer patients. J Antimicrob Chemother lE(Supp1 E):161-166, 1986. Rolston KVI, Ho DH, LeBlanc B, Bodey GP: In vitro evaluation of difloxacin (A-56619), A-56620, and other Cquinolones against isolates from cancer patients. Chemotherapy 33:419-427, 1987. Rolston KVI, Ho DH, LeBlanc B, Bodey GP: Comparativein vitro activity of the new dilluoro-quinolone temfloxacin (A-62254) against bacterial isolates from cancer patients. Eur J Clin Microbioi Infect Dis 7:684-686, 1988. Rolston K, Ho DH, LeBlanc B, Bodey G P In vitro activity of fleroxacin (Ro 23-6240), a new fluorinated 4-quinolone against isolates from cancer patients. Chemotherapy 34:448-454, 1988. Rolston KVI, LeBlanc B, Gooch G et al: In vitro activity of PD 117558, a new quinolone against bacterial isolates from cancer patients. J Antimicrob Chemother 23:363-371, 1989. Rolston KVI, Ho DH, LeBlanc R, Bodey GP: In vitro evaluation of S-25930 and S-25932, two new quinolones. against aerobic gram-negative isolates from cancer patients. Antimicrob Agents Chemother 3 1:102-103, 1987. King A, Phillips I: The comparative in vitro activity of pefloxacin. J Antiminob Chemother 17(Suppl B):l-10, 1986. Karp JE, Merz WG, Hendricksen C et al: Oral norfioxacin for prevention of gram-negative infections in patients with acute leukemia and granulocytopenia. Ann Intern Med 106:1-7, 1987. Dekker AW, Rosenberg-Arska M, Verhoef J: Infection prophylaxis in acute leukemia. A comparison of ciprofloxacin with trimethoprimlsulfamethoxazole and colistin. Ann Inter Med 106:7-12, 1987. Haron E, Rolston KVI, Cunningham C et al: Oral ciprofloxacin for infections in camer patients. J Antimicrob Chemother 24~955-962, 1989. Rolston KVI, Haron E, Cunningham C, Bodey GP: Intravenous ciprofloxacin for infections in cancer patients. Am J Med 87(Suppl 5A):2615-2655, 1989. Bodey GP, Ho DH, Elting L: Survey of antibiotic susceptibility among gram-negative bacilli at a cancer center. Am J Med 85(Suppl 1A);49-51, 1988.


Pseudomonas aerugitwsa in Cancer Patients 92. Parry MF, Panzer KB, Yukna ME: Quindone resistance. Am J Med 87(S~ppl5A):12-S-l6S, 1989. 93. Klastersky J, Meunier-Carpentier F, Prevost JM:Significance of antimimbiai synergism for the outcomeof gram-negativesepsis. Am J Med Sci 273:157-167, 1977. 94. Anderson ET, Young LS, Hewitt WL: Antimicrobial synergism in the therapy of gram-negative rod bacteremia. Chemotherapy 24~45-54, 1978. 95. Piccart M, Klastersky J, Muenier F et al: Singledrug versus combination empirical therapy for gram-negativebacillary infections in febrile cancer patients with and without granulocytopenia. Antimicrob Agents Chemother 26:870-875, 1984. %. PizzoPA, HathmJW, Hiemenz Jetal: A randomizedtrial comparing ceftazidime alone with combination antibiotic therapy in cancer patients with fever and neutropenia. N Engl J Med 315:552-558, 1986. 97. Parry MF, Neu MC, Merlin0 M et al: Treatment of pulmonary infections in patients with cystic fibrosis: a comparative study of ticarcillin and gentamicin. J Pediatr 90:144-148,, 1977. 98. Fainstein V, Bodey GP, Bolivar R et al: Moxalactamplus ticarcillinor tobramycin for treatment of febrile episodes in neutropenic cancer patients. Arch Inter Med 144:1776-1780, 1984. 99. Wmton DJ, Barner R, Ho WG et al: Moxalactam plus piperacillin versus moxalactamplus amikacin in febrilegranulocytopenicpatients. Am J Med 77:442-450, 1984. 100. Rotstein C, Cimino M,Winkey K et al: Cefopemne plus pipercillin versus mezlocillin plus tobramycin as empiric therapy for febrile episodes in neutropenic patients. Am J Med 85(Suppl 1A):36-39, 1989.

59 101. Benezra D, Kiehn TE, Gold JWM et al: Prospective study of infections in indwelling central v e m s catheten using quantitative blood cultures. Am J Med 85:495-498, 1988. 102. Young LS: The role of granulocyte transfusionsin treating and preventing infection. Cancer Treat Rep 67: 109-1 11, 1983. 103. Young LS, Meyer RD, Annstrong D: Pseudomom aeruginosa vaccine in cancer patients. AM Intern Med 79:518-527, 1973. 104. Haghbin MD, Armstrong D, Murphy ML: Controlled prospective trial of Pseudonmm aeruginosa vaccine in children with acute leukemia. Cancer 32:761-766, 1973. 105. Pennington JE, Reynolds HY, Wood RE et al: Use of a Pseudomonas aerugima vaccine in patients with acute leukemia and cystic fibrosis. Am J Med 58:629-637, 1975. 106. Stoll BJ, Pollack M, Young LS et al: Functionally active monoclonal antibody that recognizes an epitcpe on the 0 side chain of Pseudomom aeruginosa immunotype-1 lipopolysaccharide. Infect Immun 53:656462, 1986. 107. Harkonen S, Scannon P, Mischak RP et al: Phase I study of a murine monodonal anti-lipid A antibody in bacteremic and nonbacteremic patients. Antimicrob Agents Chemother 32:710-716, 1988. 108. Young LS,Grscon R, Alam S,Berrmdez LEM:Monoclonal antibodies for treatment of gram-negative infections. Rev Infect Dis ll(SUpp1 7):S1564-S1571, 1989. 109. Pizzo PA: Considerations for the prevention of infectious comlications in patients with cancer. Rev Infec Dis 11 (Suppl 7): S1551-1563, 1989.

Lipopolysaccharide pseudomonas vaccine: efficacy against pulmonary infection with Pseudomonas aeruginosa.

Vaccination against respiratory Pseudomonas aeruginosa infection.

IgG antibodies in early Pseudomonas aeruginosa infection in cystic fibrosis.

Long term chronic Pseudomonas aeruginosa airway infection in mice.

Pseudomonas aeruginosa infection in burn patients in Sulaimaniyah, Iraq: risk factors and antibiotic resistance rates.

The Role of Human Beta-Defensin-2 in Pseudomonas aeruginosa Pulmonary Infection in Cystic Fibrosis Patients.

IgG subclass antibodies to Pseudomonas aeruginosa in sera from patients with chronic Ps. aeruginosa infection investigated by ELISA.

Risk factors associated with unfavorable short-term treatment outcome in patients with documented Pseudomonas aeruginosa infection.

Comparative Study of Biofilm Formation in Pseudomonas aeruginosa Isolates from Patients of Lower Respiratory Tract Infection.

Inhaled colistin in patients with bronchiectasis and chronic Pseudomonas aeruginosa infection.

Life-threatening Pseudomonas aeruginosa infections in patients with infection due to human immunodeficiency virus.

Life-threatening Pseudomonas aeruginosa infections in patients with human immunodeficiency virus infection.

Carbapenem-resistant-only Pseudomonas aeruginosa infection in patients formerly infected by carbapenem-susceptible strains.

Nitrous oxide production in sputum from cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection.

Glycolipoprotein from Pseudomonas aeruginosa as a protective antigen against P. aeruginosa infection in mice.

Serum antibody response to Pseudomonas aeruginosa antigens during corneal infection.

Pseudomonas aeruginosa: an uncommon cause of diabetic foot infection.

Nosocomial infection with gentamicin-carbenicillin-resistant Pseudomonas aeruginosa.

Hydrogen cyanide, a volatile biomarker of Pseudomonas aeruginosa infection.

Rabbit corneal damage produced by Pseudomonas aeruginosa infection.

Antiadhesive properties of glycoclusters against Pseudomonas aeruginosa lung infection.

Genotypic analysis of Pseudomonas aeruginosa isolated from ocular infection.

Amikacin resistance developing in patients with Pseudomonas aeruginosa bronchopneumonia.

Influence of pseudomonas aeruginosa on exacerbation in patients with bronchiectasis.