Antimicrobial Drug Susceptibility of Respiratory Isolates of Haemophilus influenzae from Adults

Abstract

Haemophilus influenzae strains isolated from sputum of patients with respiratory infection of adults were tested for susceptibility to 5 antibiotics. Of the 344 strains examined, 46 (13.4%) showed MICs of 6.25μg or more of ampicillin per ml. Thirty-four of the 46 strains produced β-lactamase, whilst the remaining 12 were negative. All of the β-lactamase producing strains were sensitive to cefotaxime and chloramphenicol, but 15 (44%) were resistant to tetracycline. All of the β-lactamase-non-producing ampicillin resistant strains were sensitive to tetracycline and chloramphecicol, and 9 of 12 strains were sensitive to piperacillin. One strain showed MIC of 50μg/ml of cefotaxime. Infection mixed with ampicillin resistant and sensitive strains of H. influenzae was found in 4 patients with chronic bronchitis.