Porcine Haemophilus pleuropneumonia: microbiologic and pathologic findings.

Haemophilus pleuropneumoniae was isolated from 11% of porcine lung specimens submitted to the University of Illinois Diagnostic Laboratory during 1979-1982. Acute necrotizing fibrinous bronchopneumonia was the most common diagnosis; 65% of lungs had severe involvement of the caudal lobes; 10% of lungs had unilateral involvement only. In 46% of lungs, a second pathogen was isolated. Isolates of H pleuropneumoniae tested by the Kirby-Bauer disk method were most sensitive to nitrofurazone (100%), polymyxin B (97%), chloramphenicol (95%), gentamicin (94%), sulfachloropyridazine (87%), ampicillin (83%), and penicillin (77%). Isolates were less sensitive to 9 other antimicrobials tested. Over 4 years in 1 herd, succeeding isolates of H pleuropneumoniae developed resistance to ampicillin, streptomycin, bacitracin, lincomycin, penicillin, and tetracycline.