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- Bronchopulmonary infection caused by the Mycoplasma species, Mycoplasma pneumoniae
- Smallest free-living organism; fastidious and slow-growing; first isolated in cattle in 1898
- Most frequently affects children/young adults but can also occur in the elderly; often causes epidemics in close communities
- Infection may be asymptomatic, most often confined to the upper respiratory tract; however, may progress to pneumonia (5–10%).
- Course is usually acute with an incubation period of 1 to 4 weeks.
- Synonym(s): primary atypical pneumonia (PAP); Eaton agent pneumonia; cold agglutinin–positive pneumonia; walking pneumonia
The highest rate of ICU admissions for community-acquired pneumonia (CAP) due to M. pneumoniae occurs in seniors.
- Plays a significant role in pneumonias in children of all ages (pneumonia <5 years is more commonly viral)
- Increased incidence of asthma exacerbation in older children
- All infants 3 to 6 months with suspected bacterial pneumonia should be hospitalized.
- Estimated 1 million cases per year in the United States
- Responsible for 20% of CAP requiring hospitalizations annually
- Infection occurs most frequently in fall/winter seasons but may develop year round.
- Predominant sex: male = female
- Predominant age group affected: 5 to 20 years
- May occur at any age
- Rare in children <5 years of age
- Responsible for up to 15–20% of all cases of CAP yearly
- Most common cause of pneumonia in school children and young adults who do not have a chronic underlying condition
Etiology and Pathophysiology
- M. pneumoniae is a short-rod mucosal pathogen, which lacks a cell wall and thus not visible on Gram stain.
- Can grow under both aerobic and anaerobic conditions
- Highly contagious, M. pneumoniae is transmitted primarily by aerosol droplets.
- Pathogenicity linked to its filamentous tips, which adhere selectively to respiratory epithelial cell membrane proteins with production of H2O2 and superoxide radicals, damaging cilia
- Many pathogenic features of infection are believed to be immune-mediated, not directly induced.
- Decreased ciliary movement produces prolonged paroxysmal, hacking cough.
- Incubation period is 2 to 3 weeks.
- Infection by M. pneumoniae has come to be recognized as a worldwide cause of CAP.
- M. pneumoniae infection may worsen asthma symptoms as well as cause wheezing in children without asthma.
- Immunocompromised state (e.g., HIV, transplant recipients, chemotherapy)
- Close community living (e.g., military barracks, prisons, hospitals, dormitories, schools, household contacts)
Consider droplet isolation of active cases.
Commonly Associated Conditions
- Asthma exacerbations as a result of proinflammatory cytokine release
- Chronic obstructive pulmonary disease