Journal of Cutaneous Pathotogy

1977:4: 14-22

Cutaneous Microflora of Patients with Repeated Skin Infections MOLLIE E. McBRIDE, W. CHRISTOPHER DUNCAN AND .lOIIN M. KNOX Departments of Dermatology and Microbiology, Baylor College of Medicine, Houston, Texas, U.S.A. The microflora of normal skin in 16 patients with repeatetl staphylococcal and strejilococcal skin infections was examined to determine whether abnormalities existed which would indicate a protective role for Ihc indigenous flora against colonisation by pathogens. I'ive sites-hands, feet, axilla, groin and back-were examined quantitatively and qualitatively and compared with a control group. Total populations of indigenous llora were significantly higher from patients with repeated skin infeetions of the back, axillae and feet. The frequency of isolation of different species from normal skin was comparatile between the control and experimental groups, with the exception of the incidence of Staphytoeoeeus aureus and Proteus species which were isolated only from iwtients with repeated skin infections. (Iram-negative bacteria were isolated with coinparable frequency between the two groups, but patients with repeated skin infections tended to carry gram-negative bacteria on multiple sites. It was concluded from the high population of indigenous flora and the types of microorganisms present that the micrtjtlora of normal skin did not appear to protect patients with repeated skin infections against colonization by pathogens. The presence of high populations of Staphytoeoeeus aureus on the normal skin of patients with repeated skin infections would appear to be the most important contributing factor. {Reeeived for pubtieation Deeember 28, 1976)

The problem of repeated skin infections, usually by Staphytoeoeeus aureus, in certain individuals has long been recognized (Maibach & Hildick-Smith 1965), but factors responsible for this condition have not been satisfactorily defined. There has been increasing interest in the importance of microbial flora of normal skin in tnaintaining a stable ecological balance which might protect against patbogenic organisms. This type of control can occur in different ways: as antagonism between microbial species (or bacterial interference) which prevents colonization by the pathogen;or by the availability of the ecological space to invasion which occurs in the absence or suppression of normal flora. Both of these phenomena have been postulated as control tnechanisms of microflora of nortnal skin. Selwyn & Ellis (1972) have described the antagonistn of diphtheroids isolated from normal skin to-

wards gram-negative bacteria in vitro, postulating a protective role, and Selwyn (1975) has further attempted to correlate the presence of "antibiotic producers" from normal flora with recovery of patients from skin infections. The role of total microbial populations in maintaining an ecological balance has been postulated by Forfar et al. (1969), Taplin (1972), and Amonette & Rosenberg (1973), who showed that skin could be colonized by gratn-negative bacteria once nortnal flora had been elitninated. Control against colonization by virulent Staphylococcus aureus, by seeding with a relatively avirulent strain, has also been described (Strauss et al. 1969) supporting the view that the microflora of skin may assert sotne protective effect against colonization by a pathogen. It was the purpose of this study to define the microflora of nortnal skin of patients with

CUTANEOUS MICROFLORA AND SKIN INFECTIONS

15

a history of repeated skin infections to find Tabte 2 Subject description if any abnormalities existed either as a reduction in population of indigenous tnicroSubject group flora or the absence of any individual component which tnight serve as an antagonMedical Skin ist towards a pathogen, thus contributing to personnel infections colotiization. To accotnplish this, the tnicrobial flora of nortnal skin frotn 16 patients Number 10 16 with a lustory of reapcated skin infections Age: Range 27-32 13-68 was compared with that of a group of 10 Median 30 30 nortnal, healthy individuals. Five skin sites Using antilxicterial soap 7(70%) 8(50%) 9(90%) 7(43.5%) (palms of the hands, soles of the feet, back, Using deodorants axillae and gtoin) were chosen for both quantitative and qualitative exatnination of two groups is shown in Table 2. Although microbial flora. the age range was greater for patients with skin infections, the median age was cotnparable for the two groups. A larger proportion Material and Methods of the medical center group used antibacterial Subjects: Patients with repeated skin in- soaps and deodorants. fections were selected from the Ben Taub Dertnatology Clitiic, Veterans Administration Sampting procedures: The sites cultured Hospital dermatology ward, and from private were paltns of the hands, soles of the feet, dermatology practices. Infected lesions were and back over the scapulae, axillae, and cultured in the routine manner and bacterial groitl. liach area was cultured iti duplicate, pathogens were isolated and identified satnples being taken from both the right and (Cowan & Steel 1974). Table 1 shows the left sides of the body. The skin sampling method chosen (Shaw et al. 1970) has been Tabte t evaluated statistically and found to eompare Diagnosis ol patients with skin infections favorably with other quantitative skin sampling methods. Specimens were collected by Number of delineating a 16 cni^ area with a sterile temDiagnosis Pathogen isolated |iatieiits plate and scrubbing the skin in the area with a calciutn alginate swab tnoistened in phosFolliculitis Staphytoeoeeus aureus 4 phate buffered saline pH 7.2 containing0.1% Impetigo Streptoeoeeus pyogenes 3 Triton X 100. These swabs were suspended Group A in 2.5 till of the same buffer solution in 13 X Pyodcrma Stapliyloeoeeus aureus 9 100 tntn test tubes and shaken on a wrist Total 16 action shaker for 5 min. Following suitable dilutions, bacterial counts were made using distribution of diagnoses of the patients and pour plates of trypticase soy agar containing causative organistns isolated. All infections 0.1% Tween® 80. Qttantitation was also done were caused by gram-positive bacteria, either using Castnan's sheep blood agar and itioculaStaphyiococcus aureus ov Streptococcus pyo- ting the surface with a calibrated dropping genes Group A, or both. Since 10 of the 16 pipette. McConkey's phenylethylalcohol agar, patients in this group were hospitalized at and other selective media were used when the time of sampling and two more were necessary. Of the original suspension, 0.25 medical center personnel, medical center tnl was used to inoculate Casnian's sheep personnel were chosen as the control group blood agar for qualitative study and 0.5 tnl to minimize differences resulting from en- was inoculated into thioglycollate broth to vironmental factors. A comparison of the detect, organisms present at a low concentra-

McBRIDE ET AL.

16

tion. Plates were incubated for 3 days at 3 1 C. Routine diagnostic media and procedures were used for identification (Cowan & Steel 1974). Statiitieal procedures: The mean bacterial population was calculated from duplicate cultures taken from the right and left sides of the body from each site on each subject. The significant differences in bacterial skin populations between the groups were determined by analysis of variance followed by calculation of least significant differences when P was less than 0.05.

Table 3 A comparison of bacterial populations between patients with repeated skin infections and a control population

Axillae Control Skin infections

Mean (log,oCFU/cm= )

S.D.

P

Cutaneous microflora of patients with repeated skin infections.

Journal of Cutaneous Pathotogy 1977:4: 14-22 Cutaneous Microflora of Patients with Repeated Skin Infections MOLLIE E. McBRIDE, W. CHRISTOPHER DUNCAN...
5MB Sizes 0 Downloads 0 Views