Mycoplasma pneumoniae as a Cause of Community-Acquired Pneumonia in Children

(See the Major Article by Kutty et al on pages 5–12.)

Mycoplasma pneumoniae is a commonly identified cause of community-acquired pneumonia (CAP), particularly among school-aged children and adolescents. The absence of a cell wall, which distinguishes Mycoplasma from other pathogenic bacteria, results in resistance to recommended first-line therapy (ie, aminopenicillins) for CAP in children [1]. A high suspicion of Mycoplasma at the point of care can influence treatment decisions by prompting clinicians to instead prescribe macrolide antibiotics.

The Infectious Diseases Society of America and the Pediatric Infectious Diseases Society guideline for pediatric CAP states that macrolide antibiotics should be prescribed for treatment of children with “findings compatible with CAP caused by atypical pathogens” such as M. pneumoniae [1]. The rationale for this recommendation is that serologic and molecular test results for M. pneumoniae are rarely available in a clinically relevant time frame to influence outpatient antibiotic prescribing. Knowledge of clinical features that distinguish M. pneumoniae from viral or bacterial causes of CAP can inform empiric treatment strategies and improve clinical outcomes by encouraging targeted treatment. Despite its high prevalence, there is a paucity of comparative data to help clinicians understand how to best differentiate M. pneumoniae from other causes of CAP.

In this issue of Clinical Infectious Diseases, Kutty et al present a secondary analysis of data from the multicenter Etiology of Pneumonia in the Community (EPIC) study to describe clinical and radiologic features of CAP caused by M. pneumoniae [2]. The EPIC study, which provided insight into CAP incidence and etiology, prospectively enrolled children hospitalized with radiograph-confirmed CAP between 1 January 2010 and 30 June 2012 [3]. The current analysis focused on comparing characteristics of those with and without M. pneumoniae infection. Mycoplasma pneumoniae was detected in 182 of 2254 (8%) children aged <18 years in whom testing was performed. Most (72%) children with M. pneumoniae, but only 26% of children with other causes of CAP, were ≥5 years of age.

While the authors identified several other characteristics that were associated with higher (eg, headache, sore throat, rales, hilar lymphadenopathy) or lower (eg, wheezing, rhinorrhea, chest pain) odds of M. pneumoniae infection, none of these features reliably distinguished M. pneumoniae from other etiologies. The authors did not explore whether a combination of symptoms, signs, and radiologic features might prove more useful. Comparison of these results with existing literature is limited due to the paucity of data and heterogeneity of reporting of symptoms and signs in prior studies [4].

More than 20% of children with M. pneumoniae infection had viral codetection. This finding is not surprising in pediatrics. Respiratory pathogens are transmitted by inhalation of or mucous membrane exposure to respiratory secretions. Respiratory pathogens remain infectious on environmental surfaces, and direct or indirect mucous membrane contact with these contaminated surfaces also results in respiratory illness transmission. Normal child development, which includes chewing inedible objects and lax attention to hand hygiene, hastens transmission of respiratory pathogens in childcare and school settings. The resultant codetection, and likely coinfection, makes it challenging to attribute specific symptoms and signs to Mycoplasma vs viruses.

Notably, this study provides important, contemporary descriptive information on chest radiographic findings in children with M. pneumoniae pneumonia. Multilobar infiltrates are traditionally considered to favor M. pneumoniae. In this study, single lobar infiltrates (32%) and pleural effusions (26%) were frequently present, highlighting the difficulty in distinguishing Mycoplasma from typical bacterial causes such as Streptococcus pneumoniae. As such, M. pneumoniae ought to be considered in patients with these findings, particularly when there is suboptimal response to aminopenicillins.

Prior work has provided indirect evidence suggesting potential benefit in treating M. pneumoniae pneumonia. Prophylaxis of contacts of patients with M. pneumoniae infection with tetracycline or macrolide antibiotics reduces secondary attack rates, though seroconversion may still occur. Additionally, children with M. pneumoniae pneumonia treated with macrolide antibiotics have a shorter duration of fever and are less likely to have persistence or progression of signs and symptoms than those not treated, though these latter studies are limited by small sample sizes [5]. Pooled analyses also highlight limitations of current literature on the effectiveness of treatment for Mycoplasma, including less optimal validity and reliability of study outcomes [6]. Robust comparative data are thus lacking and the result is substantial variation in antibiotic prescribing in both outpatient and inpatient settings [7–9]. In the subset of patients with M. pneumoniae pneumonia, Kutty et al found that differences in length of stay between children who did and did not receive an inpatient antibiotic with activity against M. pneumoniae were not statistically significant [2]. Lack of differences in length of hospital stay does not preclude the possibility of therapeutic benefit. Though easily quantifiable, length of hospital stay may be influenced by many systems-level factors, making it less ideal as a primary outcome measure for studies of comparative effectiveness. This limitation should not dampen our enthusiasm for the contribution by Kutty et al but rather should reinforce their call for the conduct of a randomized clinical trial to inform whether there is a role for antimicrobials in the management of children with CAP caused by M. pneumoniae.

Note

Potential conflicts of interest. The author: No reported conflicts of interest. The author has submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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