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Published on: January 2, 2017

Susceptibility of ampicillin-resistant Haemophilus influenzae to seven penicillins

C Thornsberry, C N Baker, L A Kirven

    Antimicrobial Agents and Chemotherapy
    |January 1, 1976
    PubMed

    Insights

    Most clinical Haemophilus influenzae isolates resistant to ampicillin produce beta-lactamase. Ticarcillin and carbenicillin showed the greatest activity against these bacteria, though clinical utility remains unproven.

    Area of Science:

    • Microbiology
    • Infectious Diseases
    • Pharmacology

    Background:

    • Haemophilus influenzae is a significant human pathogen.
    • Antibiotic resistance, particularly to ampicillin, is a growing concern.
    • Beta-lactamase production is a common mechanism of resistance.

    Purpose of the Study:

    • To evaluate the susceptibility of clinical Haemophilus influenzae isolates to various penicillins.
    • To determine the prevalence of beta-lactamase production in ampicillin-resistant strains.
    • To compare the in vitro activity of different beta-lactam antibiotics.

    Main Methods:

    • Testing 67 clinical isolates of Haemophilus influenzae from the US, UK, and Germany.
    • Assessing susceptibility to penicillin, ampicillin, amoxicillin, epicillin, carbenicillin, ticarcillin, and methicillin.
    • Detecting beta-lactamase production in ampicillin-resistant and susceptible strains.
    • Determining minimal inhibitory concentrations (MICs) for comparative analysis.

    Main Results:

    • 53 of 67 isolates were ampicillin-resistant; 14 were ampicillin-susceptible.
    • Beta-lactamase was produced by 52 of the 53 ampicillin-resistant strains.
    • None of the ampicillin-susceptible strains produced beta-lactamase.
    • Ticarcillin and carbenicillin demonstrated the highest activity based on MICs.

    Conclusions:

    • Beta-lactamase production is strongly associated with ampicillin resistance in clinical Haemophilus influenzae isolates.
    • Ticarcillin and carbenicillin exhibit potent in vitro activity against these strains.
    • Further clinical studies are needed to establish the therapeutic value of ticarcillin and carbenicillin.

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