Metronidazole vs clindamycin treatment of anerobic pulmonary infection. Failure of metronidazole therapy.

Metronidazole has important in vitro bactericidal activity against strict anaerobic bacteria and has been used successfully in the treatment of infection due to these organisms. In this randomized study, the efficacy of metronidazole was compared with clindamycin in the treatment of patients with anaerobic lung abscess or necrotizing pneumonia. Six patients with lung abscesses and one with necrotizing pneumonia received metronidazole; six patients with lung abscesses, three with necrotizing pneumonia, and one with pneumonia and empyema received clindamycin. Three patients with lung abscesses and one with necrotizing pneumonia failed to respond to metronidazole treatment. One clindamycin-treated patient died of causes unrelated to antibiotic therapy. The results of this study suggest that metronidazole treatment of anaerobic pulmonary infections is less effective than currently available therapy.