Prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae. A collaborative study

Gary V. Doern, James H. Jorgensen, Clyde Thornsberry, David A. Preston

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The prevalence of antimicrobial resistance was assessed among a total of 3,356 clinical isolates of Haemophilus influenzae obtained from 22 medical centers distributed throughout the United States during the period July, 1983 through June, 1984. All strains were examined for β-lactamase production with a rapid acidometric assay and for resistance to ampicillin, chloramphenicol, cephalothin, cefamandole, cefaclor, tetracycline, and erythromycin with a standardized disk diffusion procedure. The overall rate of β-lactamase production was 15.2%, although results of disk diffusion tests suggested that the overall rate of ampicillin resistance was 19.5%. Twenty-one percent of encapsulated type b strains produced β-lactamase; 12.1% of non-type b strains were β-lactamase positive. Specific rates of β-lactamase production obtained at individual study centers varied widely with no evidence of geographic clustering. The highest rates of β-lactamase production were observed with isolates of H. influenzae recovered from infants and young children, and from blood and cerebrospinal fluid specimens. The overall rate of chloramphenicol resistance was 0.6%. The prevalence of cephalothin, cefamandole, cefaclor, tetracycline, and erythromycin resistance was 9.9%, 2.4%, 2.8%, 6.4%, and 64.2%, respectively. β-Lactamase positive isolates of H. influenzae had higher rates of resistance to all of the cephalosporins than did strains that lacked β-lactamase.

Original languageEnglish (US)
Pages (from-to)95-107
Number of pages13
JournalDiagnostic Microbiology and Infectious Disease
Issue number2
StatePublished - Feb 1986


ASJC Scopus subject areas

  • Microbiology (medical)
  • Infectious Diseases

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