The identification and antimicrobial susceptibility of anaerobic bacteria from pneumonic cattle lungs.

One hundred and forty-four lungs obtained postmortem from cattle with pneumonia were cultured for anaerobic bacteria. Forty-five lungs yielded 73 anaerobic isolates belonging to 20 species. The number of isolations of anaerobes from acute fibrinous or suppurative bronchopneumonias (32.5%) was slightly lower than from similar chronic bronchopneumonias (36.5%). Anaerobes were not recovered from 15 lungs showing macroscopic changes not of bacterial origin, nor from 13 healthy lungs. The predominant genera isolated were Bacteroides, Peptococcus, Fusobacterium and Clostridium. The most common species were P. indolicus (15 isolates), B. asaccharolyticus (nine), F. necrophorum (six), C. perfringens (four) and B. fragilis (four). There was a significant correlation between the presence of Corynebacterium pyogenes (p less than 0.001) or Escherichia coli (p less than 0.01) and the presence of anaerobes in the lungs. The isolated anaerobic bacteria were generally susceptible to ampicillin, penicillin G, cefoxitin, cephalothin, clindamycin, chloramphenicol, erythromycin, tetracycline and metronidazole. The B. fragilis and C. perfringens isolates showed multiple antibiotic resistance, and five P. indolicus isolates were resistant to tetracycline.