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ON THE NATURE OF REFRACTORINESS OF CERTAIN GRAM-NEGATIVE BACILLI TO PENICILLIN

G Shwartzman

    Science (New York, N.Y.)
    |March 16, 1945
    PubMed

    Insights

    Certain Gram-negative bacteria like E. coli and Salmonella show increased penicillin susceptibility in synthetic media. Amino acids can antagonize penicillin

    Area of Science:

    • Microbiology
    • Bacterial Physiology
    • Antimicrobial Resistance

    Background:

    • Penicillin efficacy varies significantly between different growth media.
    • Gram-negative bacteria often exhibit resistance to penicillin, a phenomenon not fully understood.
    • The role of specific nutrients in modulating antibiotic response requires further investigation.

    Purpose of the Study:

    • To investigate the influence of growth medium composition on the susceptibility of E. coli and Salmonella to penicillin.
    • To identify specific components in nutrient broths that affect penicillin's antimicrobial activity.
    • To explore the mechanisms underlying the observed differences in bacterial susceptibility.

    Main Methods:

    • Comparative susceptibility testing of E. coli and Salmonella strains.
    • Cultivation in synthetic medium versus meat infusion broth.
    • Addition of specific amino acids (casein hydrolysate, asparagine, glutamic acid) to synthetic media.
    • Assessment of methionine's effect on amino acid-mediated antagonism.

    Main Results:

    • Bacterial susceptibility to penicillin was significantly higher in synthetic medium compared to meat infusion broth.
    • Casein hydrolysate and asparagine, and to a lesser extent glutamic acid, partially antagonized penicillin's effect on E. coli in synthetic medium.
    • Methionine largely reversed the antagonistic effects of casein hydrolysate and asparagine.

    Conclusions:

    • The refractoriness of Gram-negative bacilli to penicillin is, at least partly, an extrinsic factor related to the growth environment.
    • Specific amino acids in the growth medium can modulate bacterial susceptibility to penicillin.
    • Understanding medium-dependent antibiotic efficacy is crucial for predicting and overcoming antimicrobial resistance.

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