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- Aerobic, fastidious organism.
- Organism lacks cell wall. Member of Mollicutes class, among the smallest known free-living bacteria.
- Historically termed the "Eaton agent," prior to successful cultivation in 1962.
- Believed to be a frequent cause of atypical pneumonia but diagnosis often difficult and serology inaccurate often.
- Not a part of normal human oropharyngeal flora.
- M. pneumoniae culture difficult. Growth often requires 7-21 days, successful in 40-90% of cases.
- Culture media requires heart infusion, peptone, yeast extract, salts, glucose or arginine + fetal calf serum (5-20%).
- Bacterial overgrowth a common problem.
- Erythromycin (macrolide) resistance is now described, and especially common in China (90% of isolates).
- Outbreak investigations in U.S. have found macrolide resistance rates of 8-27%.