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Outbreaks, Alerts & Hot Topics: Mycoplasma pneumoniae Pneumonia

Column Author: Chris Day, MD | Director, Transplant Infectious Disease Services; Medical Director, Travel Medicine Program

Column Editor: Angela L. Myers, MD, MPH | Division Director, Infectious Diseases; Medical Director, Center for Wellbeing

The incidence of M. pneumoniae infections is cyclical with epidemic increases usually seen every three to five years. A review of NSSP data by the CDC showed a significant decrease (from 1.15% of all pneumonia-related [all ages] ED visits to 0.35% of visits) in M. pneumoniae from prior to the COVID-19 pandemic (January 2018-April 2020) to the pandemic period (May 2020-August 2023). Incidence appeared to be again increasing September 2023-December 2023 (0.89% of visits).2 More recently, M. pneumoniae was reported in 1.8% of visits by August 2024.1

M. pneumoniae is often thought to be the cause of a particular syndrome of “walking pneumonia.” However, the presentation of M. pneumoniae pneumonia is not easily distinguishable clinically from other causes of lower respiratory tract infection.3 Clinical illness with M. pneumoniae pneumonia commonly progresses slowly over three to five days, with malaise, low-grade fevers, and cough. Chest x-rays are non-specific with various findings that can include focal lobar infiltrates, scattered multi-lobar infiltrates, or anything in between, and sometimes hilar adenopathy or pleural effusions. Laboratory markers are also non-specific: leukocytosis can be present or absent; C-reactive protein and erythrocyte sedimentation rate are often elevated. Pneumonia is not the only clinical presentation: the organism can cause an upper respiratory tract infection with features that often include sore throat, prolonged cough, or wheezing (even in patients with no underlying asthma). Asymptomatic carriage of M. pneumoniae appears to be relatively frequent and can persist for weeks or months.4 Manifestations outside of the respiratory tract are less common, but a variety of dermatologic, central nervous system and other organ system syndromes have been reported and can sometimes be severe.

Treatment for M. pneumoniae is a subject of ongoing controversy. A Cochrane review of the topic in 2015 found “insufficient evidence to draw any specific conclusions about the efficacy of antibiotics for this condition in children” based on a lack of adequately specific randomized controlled trials.5 It does not appear this situation has been rectified since. Without some basis for knowing whether and, perhaps more pertinently, how much antibiotic therapy helps, there is little basis on which to weigh the potential benefits of antibiotic therapy versus either adverse effects or the risk of selection for bacterial resistance. Extrapolation from adult studies does suggest modest benefits from either macrolides or tetracyclines. There is also evidence from Japan that children treated with macrolides for M. pneumoniae had fewer days of fever (1.5 vs. 4.0) and cough (7.0 vs. 11.4) when their strains were macrolide susceptible.4

Macrolide resistance in M. pneumoniae emerged in 2004 and has since spread worldwide. Macrolide resistance appears to be less frequent in the United States than in many other parts of the world. Resistance rates as high as 95% have been reported in China, while in the U.S. it appears that there is macrolide resistance in only 8%-13% of M. pneumoniae isolates.6,7 Macrolides remain the favored treatment for most children (typically azithromycin 10 mg/kg on day 1, followed by 5 mg/kg/day once daily on days 2-5), though doxycycline may sometimes be useful in older children (>7 years old), and levofloxacin or other quinolone antibiotics can be an option in select circumstances, including when there is demonstrated resistance.4

Diagnosis should be made based on clinical suspicion followed by specific laboratory testing to detect M. pneumoniae infection. PCR testing from upper respiratory tract samples appears to be highly sensitive and specific and is a component of the multi-pathogen respiratory panel PCR performed by the CMKC laboratory. This testing will also detect asymptomatic carriage of M. pneumoniae, which, as previously remarked, can be prolonged. Serology is also available, though even the best serologic tests likely do not outperform PCR. IgM titers begin to be detectable seven to nine days after infection. Molecular methods can be used to diagnosis macrolide resistance in M. pneumoniae obtained from respiratory specimens. Most outpatients with compatible clinical syndromes (mostly community-acquired pneumonia) will improve regardless of whether empiric antibiotic therapy includes coverage for M. pneumoniae, so testing is likely unnecessary for most of these children. Specific laboratory testing should probably be pursued in hospitalized children, especially those with suggestive clinical features, and in other patients who fail to respond to their initial regimen for community-acquired pneumonia.

 

References:

  1. Mycoplasma pneumoniae infection surveillance and trends. Centers for Disease Control and Prevention. September 20, 2024. https://www.cdc.gov/mycoplasma/php/surveillance/index.html
  2. Edens C, Clopper BR, DeVies J, et al. Notes from the field: reemergence of Mycoplasma pneumoniae infections in children and adolescents after the COVID-19 pandemic, United States, 2018–2024. MMWR Morb Mortal Wkly Rep. 2024;73:149-151. doi:10.15585/mmwr.mm7307a3
  3. Wang K, Gill P, Perera R, Thomson A, Mant D, Harnden A. Clinical symptoms and signs for the diagnosis of Mycoplasma pneumoniae in children and adolescents with community‐acquired pneumonia. Cochrane Database Syst Rev. 2012;10(10):CD009175. doi:10.1002/14651858.CD009175.pub2
  4. Bradley JS, Byington CL, Shah SS, et al. The management of community-acquired 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(7)e25-e76. https://www.idsociety.org/practice-guideline/community-acquired-pneumonia-cap-in-infants-and-children/
  5. Gardiner SJ, Gavranich JB, Chang AB. Antibiotics for community‐acquired lower respiratory tract infections secondary to Mycoplasma pneumoniae in children. Cochrane Database Syst Rev. 2015;1(1):CD004875. doi:10.1002/14651858.CD004875.pub5
  6. Leng M, Yang J, Zhou J. The molecular characteristics, diagnosis, and treatment of macrolide-resistant Mycoplasma pneumoniae in children. Front Pediatr. 2023;11:1115009. PMID: 36937963. PMCID: PMC10017863. doi:10.3389/fped.2023.1115009
  7. Zheng X, Lee S, Selvarangan R, et al. Macrolide-resistant Mycoplasma pneumoniae, United States. Emerg Infect Dis. 2015;21(8):1470-1472. doi:10.3201/eid2108.150273

 

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