REVIEW URRENT C OPINION
Mycoplasma pneumoniae in children: carriage, pathogenesis, and antibiotic resistance Patrick M. Meyer Sauteur a, Annemarie M.C. van Rossum a, and Cornelis Vink a,b
Purpose of review Both the diagnosis and treatment of Mycoplasma pneumoniae infections in children are currently facing two main challenges: a relatively high carriage in asymptomatic children, and a worldwide increase in macrolide-resistant M. pneumoniae (MRMP). This review focuses on the scientific and clinical implications of these crucial issues. Recent findings Recent studies have indicated that the prevalence of M. pneumoniae in the upper respiratory tract is similar among asymptomatic, healthy children and children with a symptomatic respiratory tract infection, and that current diagnostic procedures for M. pneumoniae are unable to differentiate between bacterial carriage and infection. It is therefore possible that the burden of M. pneumoniae-associated disease is overestimated. Another phenomenon that has an important impact on the treatment of M. pneumoniae infections is the rapid worldwide emergence of MRMP isolates. Summary The current diagnostic procedures for M. pneumoniae cannot discern between bacterial carriage and infection in a clinically relevant time frame. It is therefore imperative that these procedures be modified such as to unambiguously detect symptomatic M. pneumoniae infections. Moreover, the emergence of MRMP necessitates the application of methods to detect macrolide resistance as well as the implementation of restrictive policies regarding the use of macrolides. Keywords carriage, children, diagnosis, macrolide resistance, Mycoplasma pneumoniae
INTRODUCTION Mycoplasmas represent the smallest self-replicating organisms, both in cellular dimensions and genome size. Mycoplasma pneumoniae causes disease only in humans [1], and is one of the most common bacterial infections in children and a major cause of upper and lower respiratory tract infections. Up to 40% of the cases of childhood community-acquired pneumonia (CAP) that are admitted to the hospital are attributed to M. pneumoniae infection [2]. Although the infection is generally mild and selflimiting, patients of every age can develop severe and fulminant disease. Apart from respiratory tract infection, M. pneumoniae can also cause extrapulmonary manifestations. They occur in up to 25% of manifest M. pneumoniae infections and may affect almost every organ [3]. M. pneumoniae grows in close association with cells from its host. The absence of a cell wall and the specialized attachment organelle facilitate close www.co-infectiousdiseases.com
contact with the host respiratory epithelium, which supplies the bacterium with the necessary nutrients. The specific nature of the host–pathogen interactions at the respiratory surface may determine whether or not the bacterium will be cleared by the host, and whether the remaining, surviving bacteria cause a symptomatic infection (Fig. 1). Recent studies have indicated that the asymptomatic carriage of
a Laboratory of Pediatrics, Division of Pediatric Infectious Diseases and Immunology, Erasmus MC – Sophia Children’s Hospital, University Medical Center and bErasmus University College, Erasmus University, Rotterdam, The Netherlands
Correspondence to Dr Patrick M. Meyer Sauteur, MD, Laboratory of Pediatrics, Division of Pediatric Infectious Diseases and Immunology, Erasmus MC – Sophia Children’s Hospital, University Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. Tel: +31 10 704 39 51; fax: +31 10 704 47 61; e-mail: [email protected] Curr Opin Infect Dis 2014, 27:220–227 DOI:10.1097/QCO.0000000000000063 Volume 27 Number 3 June 2014
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Mycoplasma pneumoniae in children Meyer Sauteur et al.
KEY POINTS
infection, M. pneumoniae may remain present in the respiratory tract for weeks to months [4 ]. M. pneumoniae disease outbreaks have been reported to occur within families, schools, institutions, camps, and military bases. In 2012, the largest outbreak at a U.S. university in 35 years was reported, in which 83 M. pneumoniae-associated CAP cases were identified [11]. &&
M. pneumoniae is carried in the upper respiratory tract of asymptomatic children at high rates. Current diagnostic procedures for M. pneumoniae respiratory tract infection (Table 1) are unable to differentiate in a clinically relevant time frame between asymptomatic bacterial carriage and acute symptomatic infection. The role of M. pneumoniae in asthma is still controversial; although M. pneumoniae has been found more frequently in association with chronic asthma than acute exacerbations, it may not have a direct effect in most asthmatic children.
PATHOGENESIS AND PRESENTATION OF MYCOPLASMA PNEUMONIAE INFECTIONS
The worldwide emergence of MRMP can have important clinical consequences for treatment and progression of M. pneumoniae infections.
M. pneumoniae infections are mostly mild and selflimiting. The most common clinical syndromes are pharyngitis and acute bronchitis. The major disease burden is CAP, wherein M. pneumoniae is the second most common bacterial cause after Streptococcus pneumoniae [12], and responsible for up to 40% of cases requiring hospitalization [13,14]. Compared with other children with CAP, patients with M. pneumoniae infection may be older and have a longer duration of fever [15]. Also, the absence of wheeze and the presence of chest pain seem to increase the probability of M. pneumoniae as the causative agent [6]. However, it was concluded in a recent Cochrane review [6] that M. pneumoniae cannot be reliably diagnosed in children and adolescents on the basis of clinical symptoms and signs. Pathogenic effects of M. pneumoniae infections are assumed to be caused directly (by active infection), indirectly (by infection-induced immune mechanisms), or both (Fig. 1). M. pneumoniae is known to cause direct injury through the generation of activated oxygen. Also, a pertussis toxin-like protein encoded by M. pneumoniae has been described, that is, the community-acquired respiratory distress syndrome (CARDS) toxin, which induced disruption of the respiratory epithelium in animal models [16]. In addition to the direct damage resulting from infection by M. pneumoniae, the immunological response following infection generates inflammatory reactions that cause pulmonary and extrapulmonary symptoms. M. pneumoniae expresses adhesion proteins and glycoplipids that share structural homology with a variety of host cells (molecular mimicry), and may induce immune responses leading to cross-reactive antibodies and autoimmune damage [17 ].
The current British Thoracic Society guidelines suggest macrolide treatment for CAP in children at any age as second choice if there is no response to first-line empirical b-lactam antibiotics; in the case of very severe CAP, macrolides may be added together with the first-line regimen.
M. pneumoniae in the upper respiratory tract is high among children of every age [4 ,5 ], which may hamper the currently used diagnostic procedures. The diagnosis is further complicated because the symptoms and signs of M. pneumoniae respiratory tract infections are not reliably predictive [6]. Furthermore, studies have reported that the prevalence of macrolide-resistant M. pneumoniae (MRMP) strains among patients with respiratory symptoms is increasing worldwide [7 ]. The consequences of these findings will be discussed, and related to the diagnostic and therapeutic options for M. pneumoniae infections. &&
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CYCLIC EPIDEMICS OF MYCOPLASMA PNEUMONIAE INFECTIONS M. pneumoniae is endemic worldwide in any season, but epidemics are common, and occur in 4 to 7-year cycles [8]. The most recent epidemic in Europe occurred in 2010–2011 with a peak incidence in Finland of 145/100 000 cases in 2011 [9]. These epidemics are believed to be because of a decreasing herd immunity and different M. pneumoniae genotypes circulating in the human population [8]. M. pneumoniae is transmitted by respiratory droplets through close contact and the incubation period is 1–3 weeks. Manifest M. pneumoniae infections occur in all ages, but are usually predominant in schoolaged children and young adults [10]. Following
Respiratory tract infection
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Asthma There is a long-standing debate on the role of M. pneumoniae in asthma. Although some recent reports suggest a role for M. pneumoniae and other
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Chronic infection
Acute infection
Direct injury
Inflammation
Carriage
Invasion
M. pneumoniae Antigenic variation
Cytotoxic effects
Respiratory epithelium
Intracellular localization
Pneumonia Immunomodulation
Blood vessels
Dissemination
Antibodies and cells specific for M. pneumoniae
M. pneumoniae adherence to erythrocytes or carriage by antigen-presenting cells
Extrapulmonary manifestations
FIGURE 1. Proposed pathogenic states of Mycoplasma pneumoniae at the respiratory tract. Acute infection: M. pneumoniae attaches to the respiratory surfaces, resides mostly extracellular, and produces direct injury by a variety of local cytotoxic effects. Furthermore, it can induce inflammatory responses that result in pneumonia, and even cause extrapulmonary manifestations. The detection of M. pneumoniae at extrapulmonary sites (by culture and PCR) as well as intracellular (in vitro) suggests that M. pneumoniae may be able to invade the host. Chronic infection and carriage: antigenic variation, immunomodulation, and intracellular localization are hypothesized ways to achieve chronic disease state or carriage.
‘atypical bacteria’ in the pathogenesis of asthma [18 ,19], a recent observational study on children and adults with asthma concludes that M. pneumoniae does not have a direct role in the pathogenesis of acute and chronic asthma in most children [20 ]. M. pneumoniae infection was diagnosed in 9.4% of children with asthma (24/256) and was found more frequent in chronic asthma (13.6%) than in asthma exacerbations (7.1%) (P ¼ 0.096). The diagnosis of M. pneumoniae infection in this study was performed by PCR (n ¼ 5) and/or serology (n ¼ 28) [20 ]. Another recent study diagnosed M. pneumoniae in cases of acute asthma and refractory asthma as well as in healthy controls, but did not find significant differences between these three groups (64.2%, 65.4%, and 56.3%, respectively; P ¼ 0.6) [5 ]. However, the high detection rates reported in this study were obtained using novel diagnostic methods [CARDS toxin enzyme immunoassay (EIA) and CARDS toxin gene-specific PCR], and significant &
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variation was observed between results obtained with the CARDS toxin PCR and a more conventional P1 gene-specific PCR [5 ]. Apart from a direct role of M. pneumoniae in the pathogenesis of asthma, it has also been hypothesized that deficient immune responses to M. pneumoniae may underlie asthma. This hypothesis is based upon impaired adaptive immune responses in children with asthma and M. pneumoniae infection [5 ,19,21]. The notion that immunomodulation during M. pneumoniae infection may be a factor contributing to asthma was also supported by the induction of an allergic-type pulmonary inflammation by recombinant CARDS toxin in a mouse and baboon model [22,23]. &
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Extrapulmonary manifestations M. pneumoniae is often associated with extrapulmonary disease of almost every organ system, especially Volume 27 Number 3 June 2014
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Less sensitive and less specific than EIA
Adapted from [17 ]; for more details, see original publication. a Routine diagnostic test.
High sensitivity, high specificity
Sensitivity depends on the time point of the first serum and on the availability of paired sera (for seroconversion and/or rise in titer); ‘Gold standard’: four-fold titer increase as measured in paired sera
Moderate-high sensitivity, moderate-high specificity
Positive criteria: four-fold titer increase between acute and convalescent sera or single titer 1 : 32
Sensitivity and specificity comparable to EIA
Low sensitivity, low specificity
Low sensitivity, high specificity
High sensitivity, high specificity
Performance
Immunofluorescent assay
Serum (other bodily fluids)
Serum
Serum
Respiratory specimen (other bodily fluids or tissues)
Specimen
Immunoblotting
IgM, IgG, IgA
Enzyme immunoassay (EIA)a Proteins (e.g., adhesion protein P1) and/or glycolipids
IgM and IgG simultaneously
Igs (no discrimination between isotypes)
Crude antigen extract with glycolipids and/or proteins
Particle agglutination assay
Cold agglutinins (IgM)
–
Antibodies
Erythrocytes (I antigen)
–
Culture (isolation takes up to 21 days) Cold-agglutinin test (’bedside test’) Complement fixation test
Different target genes (e.g., P1 gene, 16S rDNA, 16S rRNA, RepMP elements, and so on)
PCRa
Direct identification of M. pneumoniae
Nonspecific serological tests for M. pneumoniae Specific serological tests for M. pneumoniae
Target/antigen
Test
Method
Table 1. Overview of diagnostic tests for Mycoplasma pneumoniae
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the skin as well as the hematologic, cardiovascular, musculoskeletal and nervous systems [3]. These manifestations may be because of either direct effects of M. pneumoniae, after dissemination of the bacteria throughout the body, or indirect effects, such as autoimmune reactions. The most frequent manifestations are diseases of the dermatologic and nervous systems. Skin findings occur in up to 25% of all M. pneumoniae infections, including mostly nonspecific exanthems, erythema nodosum, urticaria, Stevens–Johnson syndrome [24], and a rare and distinct disorder with isolated mucous membrane involvement denominated as M. pneumoniae-associated mucositis [25]. Encephalitis and Guillain–Barre´ syndrome constitute the most common and severe neurologic manifestations, wherein M. pneumoniae infection is established in up to 10 and 15% of the cases, respectively [26,27]. However, the diagnosis of these syndromes is difficult [17 ], which may be related to the high prevalence of M. pneumoniae in the population (see below), and the post-infectious autoimmune pathomechanism of these diseases. &&
diagnostic procedures that are currently used to detect acute respiratory infections with M. pneumoniae need to be reconsidered. Specifically, these procedures include (real-time) PCR, single-sample serological tests, and bacterial culture (Table 1). Although the evaluation, standardization, and optimization of these test methods are ongoing [29–31], it is questionable whether or not a ‘positive’ M. pneumoniae result in these tests actually indicates the etiological role of M. pneumoniae in all clinical cases. In that sense, the positive predictive value of these tests may be overestimated, whereas the negative predictive value may be acceptable [32]. Although the ‘gold standard’ for diagnosis of M. pneumoniae infections is considered to be a four-fold increase in total antibody titer as measured in paired sera [33], the use of convalescent sera is not considered to be useful in clinical practice because it is too time-consuming and does not allow clinicians to initiate treatment protocols in a timely fashion. Moreover, similar to carriage with S. pneumoniae, the carriage of M. pneumoniae may also induce Ig titer increases [4 ]. Clinicians therefore need to be aware of the implications and clinical significance of a positive test result, and should be knowledgeable that the current diagnostic tests may not be reliably predictive for a symptomatic M. pneumoniae infection. &&
MYCOPLASMA PNEUMONIAE IS A ‘POTENTIAL’ PATHOGEN While it is difficult to diagnose postinfectious manifestations caused by M. pneumoniae, a recent study has shown that the current diagnostic methods used for the detection of acute, respiratory disease caused by M. pneumoniae also suffer from severe shortcomings [4 ]. In this study, the prevalence of M. pneumoniae in a group of healthy children, who did not display any respiratory symptoms (n ¼ 405), was compared with that in a group of children with respiratory symptoms (n ¼ 321). Surprisingly, similar percentages of positive test results were found in the asymptomatic and symptomatic groups using M. pneumoniae-specific real-time PCR (21.1 vs. 16.2%). Likewise, both serology [immunoglobulin (Ig)M, IgG and IgA] and bacterial culture were unable to discriminate between the asymptomatic and symptomatic groups of children, which ranged in age from 3 months–16 years [4 ]. Taken together, these data indicated that M. pneumoniae is carried at relatively high rates in the upper respiratory tract of healthy children. As a consequence, M. pneumoniae should be considered as a ‘potential’ pathogen similar to other respiratory pathogens such as S. pneumoniae [28]. &&
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DIAGNOSTIC CONSEQUENCES Because the mere presence of potential pathogens in the upper respiratory tract is neither indicative nor predictive for symptomatic (respiratory) disease, the 224
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TREATMENT AND MACROLIDE RESISTANCE The first-line antibiotics for M. pneumoniae infections in children are protein synthesis inhibitors of the macrolide class [32]. Because M. pneumoniae lacks a cell wall, it is resistant to cell wall synthesis inhibitors such as b-lactam antibiotics. The 2011 British Thoracic Society guidelines for the management of CAP in children [34] suggest empiric macrolide treatment at any age if there is no response to first-line b-lactam antibiotics or in the case of very severe disease. Interestingly, a recent Cochrane review [33] concluded that there is insufficient evidence to draw any specific conclusions about the efficacy of antibiotics in the treatment of M. pneumoniae lower respiratory tract infections in children. Clearly, studies on the efficacy of antibiotics rely on a correct diagnosis as well as on monitoring of M. pneumoniae infections; as the positive predictive value of the employed diagnostic tests may have been overestimated in the past, conclusions on the efficacy of antibiotic treatment will have to be reexamined. This topic was recently discussed and reviewed elsewhere [35]. Since 2000, an alarming worldwide increase in the prevalence of (multiclonal) MRMP strains has Volume 27 Number 3 June 2014
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been witnessed [7 ,36–38]. Resistance is based on specific point mutations in domain V of the 23S rRNA (at positions 2063, 2064, and 2617), which reduces the affinity of macrolides to the bacterial ribosome [36]. Because macrolide resistance was reported to emerge during macrolide treatment, it may develop as a result of antibiotic selective pressure [39–41]. In agreement with this notion, MRMP rates are highest in countries with extensive use of macrolides [36]. In Asia, resistance rates of over 90% were reported [42 ,43 ], whereas in Europe and North America resistance rates of up to 25% were found [7 ,36]. A recent study by Zhou et al. [44 ] demonstrated that the increase in MRMP can have serious clinical consequences in children (n ¼ 206), leading to prolonged clinical symptoms (P < 0.01) and more severe radiological findings of CAP (P < 0.05). In addition, an increase in extrapulmonary manifestations was observed in patients infected with MRMP in comparison with patients infected with macrolide-sensitive strains of M. pneumoniae (29.6 vs. 10.3%; P < 0.05). Another study, however, did not reveal clinical differences between patients (adolescents and adults) being infected by either MRMP (n ¼ 30) or macrolide-sensitive strains (n ¼ 43) [45 ]. Similar findings were reported by Cardinale et al. [46 ], who found that the clinical relevance of MRMP in hospitalized CAP patients was limited to prolonging the symptoms of the disease (fever and cough) and did not increase the risk of complications. The prolongation of symptoms may be caused by a persistent immune stimulation by MRMP in the respiratory tract, as reflected by the serum levels of certain inflammatory cytokines [interferon (INF)-g, interleukin-6, and INF-g-inducible protein-10 (IP-10)], which were somewhat higher in patients infected with MRMP than in patients infected with macrolide-sensitive strains [47 ]. In agreement with the ‘macrolide resistant’ genotype of MRMP strains, the use of tetracyclines (minocycline or doxycycline) and quinolones (tosufloxacin or levofloxacin) appeared to be more effective than the use of macrolides in patients infected with MRMP [45 –47 ,48,49]. A drawback of using tetracyclines and quinolones is, however, that they may have potential toxicities in young children. Specifically, tetracyclines should not be used in children younger than 8 years of age, whereas quinolones should not be administered before adolescence [32]. Because there are no other realistic alternatives to macrolides for the treatment of M. pneumoniae infections in young children, it is important that novel antibiotics against this bacterium be found or &
developed. Interestingly, new leads toward to this goal were reported by Sun and Wang [50 ], who demonstrated that several anticancer and antiviral nucleoside and nucleobase analogs could inhibit the growth of M. pneumoniae in vitro. The inhibitory effect of these drugs most likely resulted from the inhibition of enzymes from the nucleotide biosynthesis pathway of M. pneumoniae. These enzymes may thus be exploited as potential targets for the design of new drugs against M. pneumoniae. &
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THE DEVELOPMENT OF VACCINES AGAINST M. PNEUMONIAE Apart from the discovery of novel antibiotics against M. pneumoniae, the development of vaccines against M. pneumoniae may play a crucial role in the control and/or eradication of this pathogen. Although previous attempts to produce vaccines on the basis of inactivated bacteria resulted in limited efficacy against pneumonia and various adverse effects [51], the recent use of recombinant proteins as potential vaccines was found to be promising. Specifically, the immunization of mice with the immunogenic recombinant protein of the C-terminal part of P1 (RP14) induced strong mucosal and systemic antibody responses against M. pneumoniae as well as reduced lung inflammation [52]. In another study, it was shown that immunization of guinea pigs with a chimeric protein consisting of RP14 and the P30 adhesion protein of M. pneumoniae resulted in a robust antibody response, resulting in lower bacterial loads in the respiratory tract [53 ]. These studies showed that vaccination may indeed present a future alternative to antibiotics in the combat against M. pneumoniae. Target groups for such vaccines would include young children without treatment alternatives to macrolides in countries with high MRMP rates. &&
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CONCLUSION Because current diagnostic procedures for M. pneumoniae cannot discern between bacterial carriage and infection, it is likely that the burden of M. pneumoniae-associated disease is overestimated. As a consequence, patients may be unnecessarily treated with macrolides. As the extensive use of these antibiotics may be the primary cause of the rapid, worldwide emergence of MRMP, it is crucial that novel diagnostic procedures be developed that are able to unequivocally establish the cause of respiratory tract infections. Moreover, the increasing prevalence of MRMP necessitates the generation of novel strategies against M. pneumoniae to either treat or prevent infections with this pathogen.
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Acknowledgements P.M.M.S. is funded by a Swiss National Science Foundation (SNSF) grant (PBZHP3_147290). Conflicts of interest There are no conflicts of interest.
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Mycoplasma pneumoniae in children Meyer Sauteur et al. 41. Saegeman V, Proesmans M, Dumke R. Management of macrolide-resistant Mycoplasma pneumoniae infection. Pediatr Infect Dis J 2012; 31:1210– 1211. 42. Zhao F, Liu G, Wu J, et al. Surveillance of macrolide-resistant Mycoplasma & pneumoniae in Beijing, China, from 2008 to 2012. Antimicrob Agents Chemother 2013; 57:1521–1523. This surveillance study reported the emergence of MRMP in China between 2008 and 2012, with the worldwide highest resistance rate of 97.0% MRMP strains (32/33) in 2012. 43. Hong KB, Choi EH, Lee HJ, et al. Macrolide resistance of Mycoplasma & pneumoniae, South Korea, 2000–2011. Emerg Infect Dis 2013; 19: 1281–1284. This surveillance study demonstrated the emergence of MRMP in a total of 255 isolates obtained during four consecutive epidemics in South Korea with rates of 0, 2.9, 14.7, and 62.9% in 2000, 2003, 2006, and 2010–2011, respectively. 44. Zhou Y, Zhang Y, Sheng Y, et al. More complications occurred in macrolide&& resistant Mycoplasma pneumoniae pneumonia. Antimicrob Agents Chemother 2014; 58:1034–1038. A large study that compared the clinical characteristics of children with CAP due to infections with MRMP (n ¼ 206) and macrolide-sensitive strains (n ¼ 29). They found that in children infected with MRMP, median fever duration after macrolide therapy and median hospitalization was longer (P < 0.01). Moreover, in comparison with the control group, the radiological findings were more severe and the extrapulmonary manifestations were more frequent in the MRMP-infected group (P < 0.05). 45. Miyashita N, Akaike H, Teranishi H, et al. Macrolide-resistant Mycoplasma & pneumoniae pneumonia in adolescents and adults: clinical findings, drug susceptibility, and therapeutic efficacy. Antimicrob Agents Chemother 2013; 57:5181–5185. This study did not find any difference in the clinical presentation of CAP between MRMP-infected patients (adolescents and adults) and control patients infected with macrolide-sensitive M. pneumoniae. Treatment of MRMP CAP with quinolones and minocycline was more effective than macrolide treatment (P < 0.05). 46. Cardinale F, Chironna M, Chinellato I, et al. Clinical relevance of Mycoplasma & pneumoniae macrolide resistance in children. J Clin Microbiol 2013; 51:723– 724. A comparison between MRMP-infected children and macrolide-sensitive M. pneumoniae-infected children with CAP revealed that the clinical relevance of macrolide resistance is limited to prolonging disease symptoms (fever and cough) and does not increase the risk of complications. Because of the persistence of symptoms, macrolides were replaced by levofloxacin in seven out of eight MRMPinfected cases, which was followed by the prompt resolution of the symptoms.
47. Matsuda K, Narita M, Sera N, et al. Gene and cytokine profile analysis of macrolide-resistant Mycoplasma pneumoniae infection in Fukuoka, Japan. BMC Infect Dis 2013; 13:591. This study detected MRMP in 89.2% (58/65) of M. pneumoniae infections in Japan and found that serum INF-g, interleukin-6, and IP-10 levels were higher in patients with MRMP infections than in patients infected with macrolide-sensitive M. pneumoniae strains (P < 0.001). It was hypothesized that the prolonged low degree of inflammation is related to the slightly longer duration of symptoms (P < 0.05) because of the drug resistance, and INF-g, interleukin-6, and IP-10 may serve as non-specific inflammatory markers to indicate MRMP infections. 48. Lung DC, Yip EK, Lam DS, et al. Rapid defervescence after doxycycline treatment of macrolide-resistant Mycoplasma pneumoniae associated community-acquired pneumonia in children. Pediatr Infect Dis J 2013; 32:1396– 1399. 49. Okada T, Morozumi M, Tajima T, et al. Rapid effectiveness of minocycline or doxycycline against macrolide-resistant Mycoplasma pneumoniae infection in a 2011 outbreak among Japanese children. Clin Infect Dis 2012; 55:1642– 1649. 50. Sun R, Wang L. Inhibition of Mycoplasma pneumoniae growth by FDA& approved anticancer and antiviral nucleoside and nucleobase analogs. BMC Microbiol 2013; 13:184. In this study, 23 FDA-approved anticancer or antiviral drugs showed varying inhibitory effects on M. pneumoniae growth. The mechanism of inhibition is most likely because of inhibition of enzymes in the nucleotide biosynthesis pathway and nucleoside transporter. The authors suggest that these proteins may serve as targets for future antimicrobials against M. pneumoniae. 51. Linchevski I, Klement E, Nir-Paz R. Mycoplasma pneumoniae vaccine protective efficacy and adverse reactions: systematic review and meta-analysis. Vaccine 2009; 27:2437–2446. 52. Zhu C, Wu Y, Chen S, et al. Protective immune responses in mice induced by intramuscular and intranasal immunization with a Mycoplasma pneumoniae P1C DNA vaccine. Can J Microbiol 2012; 58:644–652. 53. Hausner M, Schamberger A, Naumann W, et al. Development of protective && anti-Mycoplasma pneumoniae antibodies after immunization of guinea pigs with the combination of a P1-P30 chimeric recombinant protein and chitosan. Microb Pathog 2013; 64:23–32. In this study, guinea pigs were immunized with a chimeric protein consisting of the immunogenic C-terminal part of the P1 protein (RP14) and the P30 adhesion protein of M. pneumoniae. Systemic and intranasal booster immunizations induced a strong mucosal (IgA) and systemic antibody response, which reduced the bacterial colonization at different locations of the respiratory tract of animals infected with M. pneumoniae. &
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Mycoplasma pneumoniae in children: carriage, pathogenesis, and antibiotic resistance Patrick M. Meyer Sauteur a, Annemarie M.C. van Rossum a, and Cornelis Vink a,b
Purpose of review Both the diagnosis and treatment of Mycoplasma pneumoniae infections in children are currently facing two main challenges: a relatively high carriage in asymptomatic children, and a worldwide increase in macrolide-resistant M. pneumoniae (MRMP). This review focuses on the scientific and clinical implications of these crucial issues. Recent findings Recent studies have indicated that the prevalence of M. pneumoniae in the upper respiratory tract is similar among asymptomatic, healthy children and children with a symptomatic respiratory tract infection, and that current diagnostic procedures for M. pneumoniae are unable to differentiate between bacterial carriage and infection. It is therefore possible that the burden of M. pneumoniae-associated disease is overestimated. Another phenomenon that has an important impact on the treatment of M. pneumoniae infections is the rapid worldwide emergence of MRMP isolates. Summary The current diagnostic procedures for M. pneumoniae cannot discern between bacterial carriage and infection in a clinically relevant time frame. It is therefore imperative that these procedures be modified such as to unambiguously detect symptomatic M. pneumoniae infections. Moreover, the emergence of MRMP necessitates the application of methods to detect macrolide resistance as well as the implementation of restrictive policies regarding the use of macrolides. Keywords carriage, children, diagnosis, macrolide resistance, Mycoplasma pneumoniae
INTRODUCTION Mycoplasmas represent the smallest self-replicating organisms, both in cellular dimensions and genome size. Mycoplasma pneumoniae causes disease only in humans [1], and is one of the most common bacterial infections in children and a major cause of upper and lower respiratory tract infections. Up to 40% of the cases of childhood community-acquired pneumonia (CAP) that are admitted to the hospital are attributed to M. pneumoniae infection [2]. Although the infection is generally mild and selflimiting, patients of every age can develop severe and fulminant disease. Apart from respiratory tract infection, M. pneumoniae can also cause extrapulmonary manifestations. They occur in up to 25% of manifest M. pneumoniae infections and may affect almost every organ [3]. M. pneumoniae grows in close association with cells from its host. The absence of a cell wall and the specialized attachment organelle facilitate close www.co-infectiousdiseases.com
contact with the host respiratory epithelium, which supplies the bacterium with the necessary nutrients. The specific nature of the host–pathogen interactions at the respiratory surface may determine whether or not the bacterium will be cleared by the host, and whether the remaining, surviving bacteria cause a symptomatic infection (Fig. 1). Recent studies have indicated that the asymptomatic carriage of
a Laboratory of Pediatrics, Division of Pediatric Infectious Diseases and Immunology, Erasmus MC – Sophia Children’s Hospital, University Medical Center and bErasmus University College, Erasmus University, Rotterdam, The Netherlands
Correspondence to Dr Patrick M. Meyer Sauteur, MD, Laboratory of Pediatrics, Division of Pediatric Infectious Diseases and Immunology, Erasmus MC – Sophia Children’s Hospital, University Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. Tel: +31 10 704 39 51; fax: +31 10 704 47 61; e-mail: [email protected] Curr Opin Infect Dis 2014, 27:220–227 DOI:10.1097/QCO.0000000000000063 Volume 27 Number 3 June 2014
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Mycoplasma pneumoniae in children Meyer Sauteur et al.
KEY POINTS
infection, M. pneumoniae may remain present in the respiratory tract for weeks to months [4 ]. M. pneumoniae disease outbreaks have been reported to occur within families, schools, institutions, camps, and military bases. In 2012, the largest outbreak at a U.S. university in 35 years was reported, in which 83 M. pneumoniae-associated CAP cases were identified [11]. &&
M. pneumoniae is carried in the upper respiratory tract of asymptomatic children at high rates. Current diagnostic procedures for M. pneumoniae respiratory tract infection (Table 1) are unable to differentiate in a clinically relevant time frame between asymptomatic bacterial carriage and acute symptomatic infection. The role of M. pneumoniae in asthma is still controversial; although M. pneumoniae has been found more frequently in association with chronic asthma than acute exacerbations, it may not have a direct effect in most asthmatic children.
PATHOGENESIS AND PRESENTATION OF MYCOPLASMA PNEUMONIAE INFECTIONS
The worldwide emergence of MRMP can have important clinical consequences for treatment and progression of M. pneumoniae infections.
M. pneumoniae infections are mostly mild and selflimiting. The most common clinical syndromes are pharyngitis and acute bronchitis. The major disease burden is CAP, wherein M. pneumoniae is the second most common bacterial cause after Streptococcus pneumoniae [12], and responsible for up to 40% of cases requiring hospitalization [13,14]. Compared with other children with CAP, patients with M. pneumoniae infection may be older and have a longer duration of fever [15]. Also, the absence of wheeze and the presence of chest pain seem to increase the probability of M. pneumoniae as the causative agent [6]. However, it was concluded in a recent Cochrane review [6] that M. pneumoniae cannot be reliably diagnosed in children and adolescents on the basis of clinical symptoms and signs. Pathogenic effects of M. pneumoniae infections are assumed to be caused directly (by active infection), indirectly (by infection-induced immune mechanisms), or both (Fig. 1). M. pneumoniae is known to cause direct injury through the generation of activated oxygen. Also, a pertussis toxin-like protein encoded by M. pneumoniae has been described, that is, the community-acquired respiratory distress syndrome (CARDS) toxin, which induced disruption of the respiratory epithelium in animal models [16]. In addition to the direct damage resulting from infection by M. pneumoniae, the immunological response following infection generates inflammatory reactions that cause pulmonary and extrapulmonary symptoms. M. pneumoniae expresses adhesion proteins and glycoplipids that share structural homology with a variety of host cells (molecular mimicry), and may induce immune responses leading to cross-reactive antibodies and autoimmune damage [17 ].
The current British Thoracic Society guidelines suggest macrolide treatment for CAP in children at any age as second choice if there is no response to first-line empirical b-lactam antibiotics; in the case of very severe CAP, macrolides may be added together with the first-line regimen.
M. pneumoniae in the upper respiratory tract is high among children of every age [4 ,5 ], which may hamper the currently used diagnostic procedures. The diagnosis is further complicated because the symptoms and signs of M. pneumoniae respiratory tract infections are not reliably predictive [6]. Furthermore, studies have reported that the prevalence of macrolide-resistant M. pneumoniae (MRMP) strains among patients with respiratory symptoms is increasing worldwide [7 ]. The consequences of these findings will be discussed, and related to the diagnostic and therapeutic options for M. pneumoniae infections. &&
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CYCLIC EPIDEMICS OF MYCOPLASMA PNEUMONIAE INFECTIONS M. pneumoniae is endemic worldwide in any season, but epidemics are common, and occur in 4 to 7-year cycles [8]. The most recent epidemic in Europe occurred in 2010–2011 with a peak incidence in Finland of 145/100 000 cases in 2011 [9]. These epidemics are believed to be because of a decreasing herd immunity and different M. pneumoniae genotypes circulating in the human population [8]. M. pneumoniae is transmitted by respiratory droplets through close contact and the incubation period is 1–3 weeks. Manifest M. pneumoniae infections occur in all ages, but are usually predominant in schoolaged children and young adults [10]. Following
Respiratory tract infection
&&
Asthma There is a long-standing debate on the role of M. pneumoniae in asthma. Although some recent reports suggest a role for M. pneumoniae and other
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Chronic infection
Acute infection
Direct injury
Inflammation
Carriage
Invasion
M. pneumoniae Antigenic variation
Cytotoxic effects
Respiratory epithelium
Intracellular localization
Pneumonia Immunomodulation
Blood vessels
Dissemination
Antibodies and cells specific for M. pneumoniae
M. pneumoniae adherence to erythrocytes or carriage by antigen-presenting cells
Extrapulmonary manifestations
FIGURE 1. Proposed pathogenic states of Mycoplasma pneumoniae at the respiratory tract. Acute infection: M. pneumoniae attaches to the respiratory surfaces, resides mostly extracellular, and produces direct injury by a variety of local cytotoxic effects. Furthermore, it can induce inflammatory responses that result in pneumonia, and even cause extrapulmonary manifestations. The detection of M. pneumoniae at extrapulmonary sites (by culture and PCR) as well as intracellular (in vitro) suggests that M. pneumoniae may be able to invade the host. Chronic infection and carriage: antigenic variation, immunomodulation, and intracellular localization are hypothesized ways to achieve chronic disease state or carriage.
‘atypical bacteria’ in the pathogenesis of asthma [18 ,19], a recent observational study on children and adults with asthma concludes that M. pneumoniae does not have a direct role in the pathogenesis of acute and chronic asthma in most children [20 ]. M. pneumoniae infection was diagnosed in 9.4% of children with asthma (24/256) and was found more frequent in chronic asthma (13.6%) than in asthma exacerbations (7.1%) (P ¼ 0.096). The diagnosis of M. pneumoniae infection in this study was performed by PCR (n ¼ 5) and/or serology (n ¼ 28) [20 ]. Another recent study diagnosed M. pneumoniae in cases of acute asthma and refractory asthma as well as in healthy controls, but did not find significant differences between these three groups (64.2%, 65.4%, and 56.3%, respectively; P ¼ 0.6) [5 ]. However, the high detection rates reported in this study were obtained using novel diagnostic methods [CARDS toxin enzyme immunoassay (EIA) and CARDS toxin gene-specific PCR], and significant &
&&
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variation was observed between results obtained with the CARDS toxin PCR and a more conventional P1 gene-specific PCR [5 ]. Apart from a direct role of M. pneumoniae in the pathogenesis of asthma, it has also been hypothesized that deficient immune responses to M. pneumoniae may underlie asthma. This hypothesis is based upon impaired adaptive immune responses in children with asthma and M. pneumoniae infection [5 ,19,21]. The notion that immunomodulation during M. pneumoniae infection may be a factor contributing to asthma was also supported by the induction of an allergic-type pulmonary inflammation by recombinant CARDS toxin in a mouse and baboon model [22,23]. &
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Extrapulmonary manifestations M. pneumoniae is often associated with extrapulmonary disease of almost every organ system, especially Volume 27 Number 3 June 2014
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&&
Less sensitive and less specific than EIA
Adapted from [17 ]; for more details, see original publication. a Routine diagnostic test.
High sensitivity, high specificity
Sensitivity depends on the time point of the first serum and on the availability of paired sera (for seroconversion and/or rise in titer); ‘Gold standard’: four-fold titer increase as measured in paired sera
Moderate-high sensitivity, moderate-high specificity
Positive criteria: four-fold titer increase between acute and convalescent sera or single titer 1 : 32
Sensitivity and specificity comparable to EIA
Low sensitivity, low specificity
Low sensitivity, high specificity
High sensitivity, high specificity
Performance
Immunofluorescent assay
Serum (other bodily fluids)
Serum
Serum
Respiratory specimen (other bodily fluids or tissues)
Specimen
Immunoblotting
IgM, IgG, IgA
Enzyme immunoassay (EIA)a Proteins (e.g., adhesion protein P1) and/or glycolipids
IgM and IgG simultaneously
Igs (no discrimination between isotypes)
Crude antigen extract with glycolipids and/or proteins
Particle agglutination assay
Cold agglutinins (IgM)
–
Antibodies
Erythrocytes (I antigen)
–
Culture (isolation takes up to 21 days) Cold-agglutinin test (’bedside test’) Complement fixation test
Different target genes (e.g., P1 gene, 16S rDNA, 16S rRNA, RepMP elements, and so on)
PCRa
Direct identification of M. pneumoniae
Nonspecific serological tests for M. pneumoniae Specific serological tests for M. pneumoniae
Target/antigen
Test
Method
Table 1. Overview of diagnostic tests for Mycoplasma pneumoniae
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the skin as well as the hematologic, cardiovascular, musculoskeletal and nervous systems [3]. These manifestations may be because of either direct effects of M. pneumoniae, after dissemination of the bacteria throughout the body, or indirect effects, such as autoimmune reactions. The most frequent manifestations are diseases of the dermatologic and nervous systems. Skin findings occur in up to 25% of all M. pneumoniae infections, including mostly nonspecific exanthems, erythema nodosum, urticaria, Stevens–Johnson syndrome [24], and a rare and distinct disorder with isolated mucous membrane involvement denominated as M. pneumoniae-associated mucositis [25]. Encephalitis and Guillain–Barre´ syndrome constitute the most common and severe neurologic manifestations, wherein M. pneumoniae infection is established in up to 10 and 15% of the cases, respectively [26,27]. However, the diagnosis of these syndromes is difficult [17 ], which may be related to the high prevalence of M. pneumoniae in the population (see below), and the post-infectious autoimmune pathomechanism of these diseases. &&
diagnostic procedures that are currently used to detect acute respiratory infections with M. pneumoniae need to be reconsidered. Specifically, these procedures include (real-time) PCR, single-sample serological tests, and bacterial culture (Table 1). Although the evaluation, standardization, and optimization of these test methods are ongoing [29–31], it is questionable whether or not a ‘positive’ M. pneumoniae result in these tests actually indicates the etiological role of M. pneumoniae in all clinical cases. In that sense, the positive predictive value of these tests may be overestimated, whereas the negative predictive value may be acceptable [32]. Although the ‘gold standard’ for diagnosis of M. pneumoniae infections is considered to be a four-fold increase in total antibody titer as measured in paired sera [33], the use of convalescent sera is not considered to be useful in clinical practice because it is too time-consuming and does not allow clinicians to initiate treatment protocols in a timely fashion. Moreover, similar to carriage with S. pneumoniae, the carriage of M. pneumoniae may also induce Ig titer increases [4 ]. Clinicians therefore need to be aware of the implications and clinical significance of a positive test result, and should be knowledgeable that the current diagnostic tests may not be reliably predictive for a symptomatic M. pneumoniae infection. &&
MYCOPLASMA PNEUMONIAE IS A ‘POTENTIAL’ PATHOGEN While it is difficult to diagnose postinfectious manifestations caused by M. pneumoniae, a recent study has shown that the current diagnostic methods used for the detection of acute, respiratory disease caused by M. pneumoniae also suffer from severe shortcomings [4 ]. In this study, the prevalence of M. pneumoniae in a group of healthy children, who did not display any respiratory symptoms (n ¼ 405), was compared with that in a group of children with respiratory symptoms (n ¼ 321). Surprisingly, similar percentages of positive test results were found in the asymptomatic and symptomatic groups using M. pneumoniae-specific real-time PCR (21.1 vs. 16.2%). Likewise, both serology [immunoglobulin (Ig)M, IgG and IgA] and bacterial culture were unable to discriminate between the asymptomatic and symptomatic groups of children, which ranged in age from 3 months–16 years [4 ]. Taken together, these data indicated that M. pneumoniae is carried at relatively high rates in the upper respiratory tract of healthy children. As a consequence, M. pneumoniae should be considered as a ‘potential’ pathogen similar to other respiratory pathogens such as S. pneumoniae [28]. &&
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DIAGNOSTIC CONSEQUENCES Because the mere presence of potential pathogens in the upper respiratory tract is neither indicative nor predictive for symptomatic (respiratory) disease, the 224
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TREATMENT AND MACROLIDE RESISTANCE The first-line antibiotics for M. pneumoniae infections in children are protein synthesis inhibitors of the macrolide class [32]. Because M. pneumoniae lacks a cell wall, it is resistant to cell wall synthesis inhibitors such as b-lactam antibiotics. The 2011 British Thoracic Society guidelines for the management of CAP in children [34] suggest empiric macrolide treatment at any age if there is no response to first-line b-lactam antibiotics or in the case of very severe disease. Interestingly, a recent Cochrane review [33] concluded that there is insufficient evidence to draw any specific conclusions about the efficacy of antibiotics in the treatment of M. pneumoniae lower respiratory tract infections in children. Clearly, studies on the efficacy of antibiotics rely on a correct diagnosis as well as on monitoring of M. pneumoniae infections; as the positive predictive value of the employed diagnostic tests may have been overestimated in the past, conclusions on the efficacy of antibiotic treatment will have to be reexamined. This topic was recently discussed and reviewed elsewhere [35]. Since 2000, an alarming worldwide increase in the prevalence of (multiclonal) MRMP strains has Volume 27 Number 3 June 2014
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Mycoplasma pneumoniae in children Meyer Sauteur et al. &
been witnessed [7 ,36–38]. Resistance is based on specific point mutations in domain V of the 23S rRNA (at positions 2063, 2064, and 2617), which reduces the affinity of macrolides to the bacterial ribosome [36]. Because macrolide resistance was reported to emerge during macrolide treatment, it may develop as a result of antibiotic selective pressure [39–41]. In agreement with this notion, MRMP rates are highest in countries with extensive use of macrolides [36]. In Asia, resistance rates of over 90% were reported [42 ,43 ], whereas in Europe and North America resistance rates of up to 25% were found [7 ,36]. A recent study by Zhou et al. [44 ] demonstrated that the increase in MRMP can have serious clinical consequences in children (n ¼ 206), leading to prolonged clinical symptoms (P < 0.01) and more severe radiological findings of CAP (P < 0.05). In addition, an increase in extrapulmonary manifestations was observed in patients infected with MRMP in comparison with patients infected with macrolide-sensitive strains of M. pneumoniae (29.6 vs. 10.3%; P < 0.05). Another study, however, did not reveal clinical differences between patients (adolescents and adults) being infected by either MRMP (n ¼ 30) or macrolide-sensitive strains (n ¼ 43) [45 ]. Similar findings were reported by Cardinale et al. [46 ], who found that the clinical relevance of MRMP in hospitalized CAP patients was limited to prolonging the symptoms of the disease (fever and cough) and did not increase the risk of complications. The prolongation of symptoms may be caused by a persistent immune stimulation by MRMP in the respiratory tract, as reflected by the serum levels of certain inflammatory cytokines [interferon (INF)-g, interleukin-6, and INF-g-inducible protein-10 (IP-10)], which were somewhat higher in patients infected with MRMP than in patients infected with macrolide-sensitive strains [47 ]. In agreement with the ‘macrolide resistant’ genotype of MRMP strains, the use of tetracyclines (minocycline or doxycycline) and quinolones (tosufloxacin or levofloxacin) appeared to be more effective than the use of macrolides in patients infected with MRMP [45 –47 ,48,49]. A drawback of using tetracyclines and quinolones is, however, that they may have potential toxicities in young children. Specifically, tetracyclines should not be used in children younger than 8 years of age, whereas quinolones should not be administered before adolescence [32]. Because there are no other realistic alternatives to macrolides for the treatment of M. pneumoniae infections in young children, it is important that novel antibiotics against this bacterium be found or &
developed. Interestingly, new leads toward to this goal were reported by Sun and Wang [50 ], who demonstrated that several anticancer and antiviral nucleoside and nucleobase analogs could inhibit the growth of M. pneumoniae in vitro. The inhibitory effect of these drugs most likely resulted from the inhibition of enzymes from the nucleotide biosynthesis pathway of M. pneumoniae. These enzymes may thus be exploited as potential targets for the design of new drugs against M. pneumoniae. &
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THE DEVELOPMENT OF VACCINES AGAINST M. PNEUMONIAE Apart from the discovery of novel antibiotics against M. pneumoniae, the development of vaccines against M. pneumoniae may play a crucial role in the control and/or eradication of this pathogen. Although previous attempts to produce vaccines on the basis of inactivated bacteria resulted in limited efficacy against pneumonia and various adverse effects [51], the recent use of recombinant proteins as potential vaccines was found to be promising. Specifically, the immunization of mice with the immunogenic recombinant protein of the C-terminal part of P1 (RP14) induced strong mucosal and systemic antibody responses against M. pneumoniae as well as reduced lung inflammation [52]. In another study, it was shown that immunization of guinea pigs with a chimeric protein consisting of RP14 and the P30 adhesion protein of M. pneumoniae resulted in a robust antibody response, resulting in lower bacterial loads in the respiratory tract [53 ]. These studies showed that vaccination may indeed present a future alternative to antibiotics in the combat against M. pneumoniae. Target groups for such vaccines would include young children without treatment alternatives to macrolides in countries with high MRMP rates. &&
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CONCLUSION Because current diagnostic procedures for M. pneumoniae cannot discern between bacterial carriage and infection, it is likely that the burden of M. pneumoniae-associated disease is overestimated. As a consequence, patients may be unnecessarily treated with macrolides. As the extensive use of these antibiotics may be the primary cause of the rapid, worldwide emergence of MRMP, it is crucial that novel diagnostic procedures be developed that are able to unequivocally establish the cause of respiratory tract infections. Moreover, the increasing prevalence of MRMP necessitates the generation of novel strategies against M. pneumoniae to either treat or prevent infections with this pathogen.
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Acknowledgements P.M.M.S. is funded by a Swiss National Science Foundation (SNSF) grant (PBZHP3_147290). Conflicts of interest There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Waites KB, Talkington DF. Mycoplasma pneumoniae and its role as a human pathogen. Clin Microbiol Rev 2004; 17:697–728; table of contents. 2. Principi N, Esposito S. Emerging role of Mycoplasma pneumoniae and Chlamydia pneumoniae in paediatric respiratory-tract infections. Lancet Infect Dis 2001; 1:334–344. 3. Narita M. Pathogenesis of extrapulmonary manifestations of Mycoplasma pneumoniae infection with special reference to pneumonia. J Infect Chemother 2010; 16:162–169. 4. Spuesens EB, Fraaij PL, Visser EG, et al. Carriage of Mycoplasma pneumo&& niae in the upper respiratory tract of symptomatic and asymptomatic children: an observational study. PLoS Med 2013; 10:e1001444. This observational study detected M. pneumoniae DNA in 21.2% of asymptomatic children (n ¼ 405) and in 16.2% of symptomatic children (n ¼ 321) in the Netherlands (P ¼ 0.11). Neither serology, quantitative PCR nor culture differentiated asymptomatic carriage from infection, suggesting that current diagnostic tests for M. pneumoniae are unable to discriminate between asymptomatic carriage and symptomatic infection. Two or more pathogens were found in 56.2% (63/112) of asymptomatic children and in 55.5% (50/90) of symptomatic children. 5. Wood PR, Hill VL, Burks ML, et al. Mycoplasma pneumoniae in children with & acute and refractory asthma. Ann Allergy Asthma Immunol 2013; 110:328– 334e1. This study detected M. pneumoniae by new diagnostic methods (CARDS toxin EIA and PCR) as well as conventional PCR in 56.3% of healthy controls, 64.2% of patients with acute asthma, and 65.4% of patients with refractory asthma. Children with asthma had lower antibody levels to M. pneumoniae compared with healthy controls. 6. Wang K, Gill P, Perera R, et al. Clinical symptoms and signs for the diagnosis of Mycoplasma pneumoniae in children and adolescents with community-acquired pneumonia. Cochrane Database Syst Rev 2012; 10:CD009175. 7. Principi N, Esposito S. Macrolide-resistant Mycoplasma pneumoniae: its role & in respiratory infection. J Antimicrob Chemother 2013; 68:506–511. This review presents an update of the knowledge on MRMP and discusses treatment approaches in MRMP-infected patients. 8. Jacobs E. Mycoplasma pneumoniae: now in the focus of clinicians and epidemiologists. Euro Surveill 2012; 17:1–3. 9. Polkowska A, Harjunpaa A, Toikkanen S, et al. Increased incidence of Mycoplasma pneumoniae infection in Finland, 2010-2011. Euro Surveill 2012; 17:pii: 20072. 10. Foy HM. Infections caused by Mycoplasma pneumoniae and possible carrier state in different populations of patients. Clin Infect Dis 1993; 17 (Suppl 1): S37–46. 11. Centers for Disease Control and Prevention (CDC). Mycoplasma pneumoniae outbreak at a university - Georgia, 2012. MMWR Morb Mortal Wkly Rep 2013; 62:603–606. 12. Michelow IC, Olsen K, Lozano J, et al. Epidemiology and clinical characteristics of community-acquired pneumonia in hospitalized children. Pediatrics 2004; 113:701–707. 13. Baer G, Engelcke G, Abele-Horn M, et al. Role of Chlamydia pneumoniae and Mycoplasma pneumoniae as causative agents of community-acquired pneumonia in hospitalised children and adolescents. Eur J Clin Microbiol Infect Dis 2003; 22:742–745. 14. Principi N, Esposito S, Blasi F, et al. Role of Mycoplasma pneumoniae and Chlamydia pneumoniae in children with community-acquired lower respiratory tract infections. Clin Infect Dis 2001; 32:1281–1289. 15. Fischer JE, Steiner F, Zucol F, et al. Use of simple heuristics to target macrolide prescription in children with community-acquired pneumonia. Arch Pediatr Adolesc Med 2002; 156:1005–1008. 16. Kannan TR, Baseman JB. ADP-ribosylating and vacuolating cytotoxin of Mycoplasma pneumoniae represents unique virulence determinant among bacterial pathogens. Proc Natl Acad Sci U S A 2006; 103: 6724–6729.
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17. Meyer Sauteur PM, Jacobs BC, Spuesens EBM, et al. Antibody responses to Mycoplasma pneumoniae: role in pathogenesis and diagnosis of encephalitis? PLoS Pathog 2014 (in press). This review of a multinational group focuses on the role of antibody responses against M. pneumoniae in the pathogenesis of nervous system diseases, for example, encephalitis and Guillain–Barre´ syndrome. 18. Atkinson TP. Is asthma an infectious disease? New evidence. Curr Allergy & Asthma Rep 2013; 13:702–709. This review examines the current data regarding the impact of infections on asthma, and provides a mini-review on the possible role of M. pneumoniae in the pathogenesis of asthma (p. 705–706). 19. Smith-Norowitz TA, Silverberg JI, Kusonruksa M, et al. Asthmatic children have increased specific anti-Mycoplasma pneumoniae IgM but not IgG or IgEvalues independent of history of respiratory tract infection. Pediatr Infect Dis J 2013; 32:599–603. 20. Bebear C, Raherison C, Nacka F, et al. Comparison of Mycoplasma pneu&& moniae infections in asthmatic children versus asthmatic adults. Pediatr Infect Dis J 2013; 33:e71–e75. A prospective observational multicenter cohort study to investigate the role of M. pneumoniae infections in 256 children and 68 adults with asthma in France. M. pneumoniae infection was diagnosed in 9.4% of children and 7.4% of adults with asthma, suggesting that M. pneumoniae does not play a direct role in the pathogenesis of asthma in most children. 21. Atkinson TP, Duffy LB, Pendley D, et al. Deficient immune response to Mycoplasma pneumoniae in childhood asthma. Allergy Asthma Proc 2009; 30:158–165. 22. Medina JL, Coalson JJ, Brooks EG, et al. Mycoplasma pneumoniae CARDS toxin induces pulmonary eosinophilic and lymphocytic inflammation. Am J Respir Cell Mol Biol 2012; 46:815–822. 23. Hardy RD, Coalson JJ, Peters J, et al. Analysis of pulmonary inflammation and function in the mouse and baboon after exposure to Mycoplasma pneumoniae CARDS toxin. PLoS One 2009; 4:e7562. 24. Schalock PC, Dinulos JG. Mycoplasma pneumoniae-induced cutaneous disease. Int J Dermatol 2009; 48:673–680; quiz 680–681. 25. Meyer Sauteur PM, Goetschel P, Lautenschlager S. Mycoplasma pneumoniae and mucositis–part of the Stevens-Johnson syndrome spectrum. J Dtsch Dermatol Ges 2012; 10:740–746. 26. Bitnun A, Ford-Jones EL, Petric M, et al. Acute childhood encephalitis and Mycoplasma pneumoniae. Clin Infect Dis 2001; 32:1674–1684. 27. Sinha S, Prasad KN, Jain D, et al. Preceding infections and antiganglioside antibodies in patients with Guillain-Barre´ syndrome: a single centre prospective case-control study. Clin Microbiol Infect 2007; 13:334– 337. 28. Riordan A. In children with respiratory symptoms are Mycoplasma pneumoniae PCR and serology clinically significant? Arch Dis Child Educ Pract Ed 2014. [Epub ahead of print] 29. Loens K, Goossens H, Ieven M. Acute respiratory infection due to Mycoplasma pneumoniae: current status of diagnostic methods. Eur J Clin Microbiol Infect Dis 2010; 29:1055–1069. 30. Waites KB, Duffy LB, Bebear CM, et al. Standardized methods and quality control limits for agar and broth microdilution susceptibility testing of Mycoplasma pneumoniae, Mycoplasma hominis, and Ureaplasma urealyticum. J Clin Microbiol 2012; 50:3542–3547. 31. Dumke R, Strubel A, Cyncynatus C, et al. Optimized serodiagnosis of Mycoplasma pneumoniae infections. Diagn Microbiol Infect Dis 2012; 73:200–203. 32. Bradley JS, Byington CL, Shah SS, et al. The management of communityacquired pneumonia in infants and children older than 3 months of age: clinical practice guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America. Clin Infect Dis 2011; 53:e25– e76. 33. Mulholland S, Gavranich JB, Chang AB. Antibiotics for community-acquired lower respiratory tract infections secondary to Mycoplasma pneumoniae in children. Cochrane Database Syst Rev 2010; 7:CD004875. 34. Harris M, Clark J, Coote N, et al. British Thoracic Society guidelines for the management of community acquired pneumonia in children: update 2011. Thorax 2011; 66 (Suppl 2):ii1–ii23. 35. Spuesens EBM, Meyer Sauteur PM, Vink C, et al. Mycoplasma pneumoniae infections: does treatment help? J Infect 2014 (in press). 36. Bebear C, Pereyre S, Peuchant O. Mycoplasma pneumoniae: susceptibility and resistance to antibiotics. Future Microbiol 2011; 6:423–431. 37. Liu Y, Ye X, Zhang H, et al. Multiclonal origin of macrolide-resistant Mycoplasma pneumoniae isolates as determined by multilocus variablenumber tandem-repeat analysis. J Clin Microbiol 2012; 50:2793– 2795. 38. Pereyre S, Charron A, Hidalgo-Grass C, et al. The spread of Mycoplasma pneumoniae is polyclonal in both an endemic setting in France and in an epidemic setting in Israel. PLoS One 2012; 7:e38585. 39. Chironna M, Sallustio A, Esposito S, et al. Emergence of macrolide-resistant strains during an outbreak of Mycoplasma pneumoniae infections in children. J Antimicrob Chemother 2011; 66:734–737. 40. Cardinale F, Chironna M, Dumke R, et al. Macrolide-resistant Mycoplasma pneumoniae in paediatric pneumonia. Eur Respir J 2011; 37:1522– 1524. &&
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Mycoplasma pneumoniae in children Meyer Sauteur et al. 41. Saegeman V, Proesmans M, Dumke R. Management of macrolide-resistant Mycoplasma pneumoniae infection. Pediatr Infect Dis J 2012; 31:1210– 1211. 42. Zhao F, Liu G, Wu J, et al. Surveillance of macrolide-resistant Mycoplasma & pneumoniae in Beijing, China, from 2008 to 2012. Antimicrob Agents Chemother 2013; 57:1521–1523. This surveillance study reported the emergence of MRMP in China between 2008 and 2012, with the worldwide highest resistance rate of 97.0% MRMP strains (32/33) in 2012. 43. Hong KB, Choi EH, Lee HJ, et al. Macrolide resistance of Mycoplasma & pneumoniae, South Korea, 2000–2011. Emerg Infect Dis 2013; 19: 1281–1284. This surveillance study demonstrated the emergence of MRMP in a total of 255 isolates obtained during four consecutive epidemics in South Korea with rates of 0, 2.9, 14.7, and 62.9% in 2000, 2003, 2006, and 2010–2011, respectively. 44. Zhou Y, Zhang Y, Sheng Y, et al. More complications occurred in macrolide&& resistant Mycoplasma pneumoniae pneumonia. Antimicrob Agents Chemother 2014; 58:1034–1038. A large study that compared the clinical characteristics of children with CAP due to infections with MRMP (n ¼ 206) and macrolide-sensitive strains (n ¼ 29). They found that in children infected with MRMP, median fever duration after macrolide therapy and median hospitalization was longer (P < 0.01). Moreover, in comparison with the control group, the radiological findings were more severe and the extrapulmonary manifestations were more frequent in the MRMP-infected group (P < 0.05). 45. Miyashita N, Akaike H, Teranishi H, et al. Macrolide-resistant Mycoplasma & pneumoniae pneumonia in adolescents and adults: clinical findings, drug susceptibility, and therapeutic efficacy. Antimicrob Agents Chemother 2013; 57:5181–5185. This study did not find any difference in the clinical presentation of CAP between MRMP-infected patients (adolescents and adults) and control patients infected with macrolide-sensitive M. pneumoniae. Treatment of MRMP CAP with quinolones and minocycline was more effective than macrolide treatment (P < 0.05). 46. Cardinale F, Chironna M, Chinellato I, et al. Clinical relevance of Mycoplasma & pneumoniae macrolide resistance in children. J Clin Microbiol 2013; 51:723– 724. A comparison between MRMP-infected children and macrolide-sensitive M. pneumoniae-infected children with CAP revealed that the clinical relevance of macrolide resistance is limited to prolonging disease symptoms (fever and cough) and does not increase the risk of complications. Because of the persistence of symptoms, macrolides were replaced by levofloxacin in seven out of eight MRMPinfected cases, which was followed by the prompt resolution of the symptoms.
47. Matsuda K, Narita M, Sera N, et al. Gene and cytokine profile analysis of macrolide-resistant Mycoplasma pneumoniae infection in Fukuoka, Japan. BMC Infect Dis 2013; 13:591. This study detected MRMP in 89.2% (58/65) of M. pneumoniae infections in Japan and found that serum INF-g, interleukin-6, and IP-10 levels were higher in patients with MRMP infections than in patients infected with macrolide-sensitive M. pneumoniae strains (P < 0.001). It was hypothesized that the prolonged low degree of inflammation is related to the slightly longer duration of symptoms (P < 0.05) because of the drug resistance, and INF-g, interleukin-6, and IP-10 may serve as non-specific inflammatory markers to indicate MRMP infections. 48. Lung DC, Yip EK, Lam DS, et al. Rapid defervescence after doxycycline treatment of macrolide-resistant Mycoplasma pneumoniae associated community-acquired pneumonia in children. Pediatr Infect Dis J 2013; 32:1396– 1399. 49. Okada T, Morozumi M, Tajima T, et al. Rapid effectiveness of minocycline or doxycycline against macrolide-resistant Mycoplasma pneumoniae infection in a 2011 outbreak among Japanese children. Clin Infect Dis 2012; 55:1642– 1649. 50. Sun R, Wang L. Inhibition of Mycoplasma pneumoniae growth by FDA& approved anticancer and antiviral nucleoside and nucleobase analogs. BMC Microbiol 2013; 13:184. In this study, 23 FDA-approved anticancer or antiviral drugs showed varying inhibitory effects on M. pneumoniae growth. The mechanism of inhibition is most likely because of inhibition of enzymes in the nucleotide biosynthesis pathway and nucleoside transporter. The authors suggest that these proteins may serve as targets for future antimicrobials against M. pneumoniae. 51. Linchevski I, Klement E, Nir-Paz R. Mycoplasma pneumoniae vaccine protective efficacy and adverse reactions: systematic review and meta-analysis. Vaccine 2009; 27:2437–2446. 52. Zhu C, Wu Y, Chen S, et al. Protective immune responses in mice induced by intramuscular and intranasal immunization with a Mycoplasma pneumoniae P1C DNA vaccine. Can J Microbiol 2012; 58:644–652. 53. Hausner M, Schamberger A, Naumann W, et al. Development of protective && anti-Mycoplasma pneumoniae antibodies after immunization of guinea pigs with the combination of a P1-P30 chimeric recombinant protein and chitosan. Microb Pathog 2013; 64:23–32. In this study, guinea pigs were immunized with a chimeric protein consisting of the immunogenic C-terminal part of the P1 protein (RP14) and the P30 adhesion protein of M. pneumoniae. Systemic and intranasal booster immunizations induced a strong mucosal (IgA) and systemic antibody response, which reduced the bacterial colonization at different locations of the respiratory tract of animals infected with M. pneumoniae. &
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