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Antimicrobial Synergy Testing by the Inkjet Printer-assisted Automated Checkerboard Array and the Manual Time-kill Method
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Published on: April 18, 2019

Activity of amoxycillin against enterococci and synergism with aminoglycoside antibiotics

E J Russell, R Sutherland

    Journal of Medical Microbiology
    |February 1, 1975
    PubMed

    Insights

    Amoxycillin demonstrated superior in vitro activity against enterococci compared to ampicillin and benzylpenicillin. Combining penicillins with sensitive aminoglycosides achieved synergistic bactericidal effects, sterilizing cultures.

    Area of Science:

    • Microbiology
    • Infectious Diseases
    • Pharmacology

    Background:

    • Enterococci are significant pathogens, often requiring combination antibiotic therapy.
    • Understanding antibiotic resistance patterns and synergistic effects is crucial for effective treatment.
    • Penicillins and aminoglycosides are commonly used against enterococcal infections.

    Purpose of the Study:

    • To evaluate the in vitro activity of amoxycillin, ampicillin, and benzylpenicillin against clinical enterococcal isolates.
    • To assess the synergistic bactericidal effects of penicillin-aminoglycoside combinations.
    • To determine the impact of aminoglycoside resistance on combination therapy efficacy.

    Main Methods:

    • In vitro susceptibility testing of 55 clinical enterococcal isolates against various penicillins and aminoglycosides.
    • Evaluation of bactericidal activity and culture sterilization using penicillin-aminoglycoside combinations.
    • Analysis of synergistic effects based on isolate susceptibility to individual antibiotics.

    Main Results:

    • Amoxycillin exhibited greater in vitro activity than ampicillin or benzylpenicillin against enterococci.
    • All tested strains were sensitive to penicillins, but some showed high-level resistance to streptomycin and kanamycin.
    • Gentamicin was the most potent aminoglycoside; penicillin-aminoglycoside combinations showed synergy and sterilized cultures when enterococci were sensitive to the aminoglycoside.

    Conclusions:

    • Amoxycillin may offer advantages over ampicillin or benzylpenicillin for treating enterococcal infections.
    • Synergistic bactericidal activity is achievable with penicillin-aminoglycoside combinations, but only if the enterococcus is susceptible to the aminoglycoside.
    • High-level aminoglycoside resistance can preclude synergistic killing, highlighting the importance of susceptibility testing.

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