Antimicrobial resistance of Haemophilus species in patients with chronic bronchitis.

Haemophilus influenzae strains resistant to ampicillin have become an important cause of disease in pediatric patients. Because many adults with chronic bronchitis carry Haemophilus organisms in their tracheobronchial tree and because antimicrobial agents are used commonly in these patients, we assessed the prevalence of resistance to ampicillin and other antimicrobial agents in this population. We studied 150 Haemophilus isolates (73 H. influenzae, 69 H. parainfluenzae, 6 H. parahemolyticus, and 2 H. hemolyticus) obtained from 138 patients with chronic bronchitis from January 1978 through March 1979. Ampicillin resistance due to production of beta-lactamase was found in 7 of the 150 isolates (4.7 %)-2 H. influenzae, 4 H. parainfluenzae and 1 H. parahemolyticus. Resistance to tetracycline was found in 9 strains (6 %), but all strains were susceptible to chloramphenicol.