Pulmonary infection due to anaerobes in a hospital autopsy survey

Postmortem bacteriologic examination was performed to determine causative organisms in nosocomial or terminal pneumonia for a 10-year period. Most of the patients had severe underlying diseases such as lung cancer (92 cases), leukemia (101), malignant lymphoma (90), and others (85). The materials were obtained by percutaneous aspiration of lung and heart immediately after death or directly from lung and heart after opening the thorax at autopsy. Anaerobic bacteriologic methods were employed for isolation. Twenty-one strains of anaerobic bacteria were recovered (3.4% of the 603 total isolates) from the lungs for 368 cases, and 16 strains (6.5%) of anaerobic bacteria were isolated among 247 strains from heart blood for 314 cases. Bacteroides fragilis was the most frequently isolated anaerobe from both the lungs and heart blood. The same bacterium was isolated from both the lungs and heart blood of four autopsied patients; from three of these patients only B. fragilis was isolated. Enteric gram-negative bacilli and Pseudomonas were common in the patients with nosocomial pneumonia; these patients usually had received many antibiotics before death. The results indicate that anaerobes are not common in fatal nosocomial or other types of pneumonia in the hospital setting, but B. fragilis is relatively important among the anaerobes isolated. However, because of technical considerations, this report must be considered preliminary, and a more definitive study is desirable.