Etiologies and treatment outcomes for out-patients with community-acquired pneumonia (CAP) at Srinagarind Hospital, Khon Kaen, Thailand.

Most patients with community-acquired pneumonia are treated as out-patients with empirical therapy, since initially the etiologic agent is unknown. We prospectively assessed the etiologies and treatment outcomes of pneumonia from February 2003 to 2004 at ambulatory clinics. Forty-four patients were included with a mean age of 49.2 (SD 18.2) years. The male to female ratio was 1:1.4. The incubation period was 6.9 (SD 4.4) days. Half of the patients were healthy. Asthma and COPD were common in patients with underlying diseases. The etiologic diagnosis was determined by a sputum culture and a serology test of paired serum samples. Hemo-culture produced no growth in any patients. Atypical pathogens and H. influenzae were the most common finding, each occurring in 31.8% of the patients followed by S. pneumoniae and H. parainfluenzae (27.3% each). Twenty-two patients were infected with multiple pathogens. C. pneumoniae was the most common co-infecting pathogen. Two of 12 S. pneumoniae isolates were penicillin resistant. Nine of 14 H. influenzae isolates were cotrimoxazole resistant and 8 of 14 were not sensitive to erythromycin. For H. parainfluenzae, 11 of 12 isolates were not sensitive to erythromycin, and 7 of 12 were not sensitive to cotrimoxazole. Oral antibiotics were prescribed as out-patient treatment. Forty patients (90.9%) improved, with symptoms-score improvement averaging 6.4 days. Four patients got worse and needed a change of antibiotics, the symptoms usually worsen within 3-5 days. We conclude that, antibiotics for CAP out-patients should cover atypical pathogens, H. influenzae, S. pneumoniae and H. parainfluenzae. If the clinical symptoms do not respond after 3-5 days of out-patient treatment, resistance or an unusual organism (eg B. pseudomallei) should be considered.