RESUMEN
BACKGROUND: Mycoplasma pneumoniae is one of the common causes of community-acquired pneumonia (CAP) in children and young adults. In Thailand, there has been no prospective study to evaluate the prevalence, clinical features and laboratory findings of M. pneumoniae in adult patients with CAP. METHOD: The authors prospectively investigated the cause of CAP in adult patients at three general hospitals from September 1998 to August 1999. Paired sera were tested for M. pneumoniae infection by using particle agglutination and definite diagnosis was based on a fourfold increase in antibody titer. RESULTS: Seventeen (21.3%) of 80 patients had pneumonia due to M. pneumoniae. Mean age was 28.3 years old (range 18-40). The most common clinical manifestations were cough (100% of cases), fever (82.4% of cases), and headache (47% of cases). Eighty-eight per cent of these patients were classified as class I category, according to the ATS guideline. All patients had a white blood cell count between 4,000-12,000 cells/mm3. In addition, the common radiographic manifestations were alveolar shadowing (53%), and mixed alveolar and interstitial shadowing (29.4%). Sixteen cases (94%) were treated with the appropriate antibiotic and all patients survived without complication. CONCLUSION: These findings suggest that M. pneumoniae is a common cause of CAP in Bangkok, Thailand. This type of pneumonia usually occurs in young adults and can usually be treated as ambulatory patients.