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EFFECT OF SUBLETHAL CONCENTRATIONS OF PENICILLIN ON THE VIRULENCE AND ANTIGENIC COMPOSITION OF GROUP A STREPTOCOCCI

J G MICHAEL, B F MASSELL, R E PERKINS

    Journal of Bacteriology
    |June 1, 1963
    PubMed

    Insights

    Sublethal penicillin concentrations reduced group A streptococci virulence and M protein. However, these penicillin-resistant variants regained virulence and antigenic properties after passage through mice.

    Area of Science:

    • Microbiology
    • Bacteriology
    • Immunology

    Background:

    • Group A streptococci are significant human pathogens.
    • Penicillin is a primary antibiotic for treating streptococcal infections.
    • Understanding antibiotic effects on bacterial virulence is crucial for effective treatment.

    Purpose of the Study:

    • To investigate the impact of sublethal penicillin concentrations on group A streptococci.
    • To assess changes in bacterial virulence and antigenic composition.
    • To identify potential development of antibiotic resistance and its reversibility.

    Main Methods:

    • Group A streptococci strains were cultured in sublethal penicillin concentrations.
    • Colonial morphology, virulence in mice, and antigenic composition (Group A and M protein) were assessed.
    • Bacterial variants were analyzed for penicillin resistance, blood hemolysis, and susceptibility to human blood.

    Main Results:

    • Sublethal penicillin reduced M protein and group A substance.
    • Multiple transfers yielded penicillin-resistant variants lacking group/type substances.
    • These variants were avirulent in mice and susceptible to normal human blood.
    • Two of three strains lost beta-hemolysis production.
    • In vivo passage through mice restored original properties to variants.

    Conclusions:

    • Sublethal penicillin can induce transient changes in streptococcal virulence and antigenicity.
    • Penicillin-resistant variants can emerge but may lose virulence.
    • In vivo passage can reverse induced avirulence and penicillin resistance.
    • These findings highlight the complex interplay between antibiotics, bacterial adaptation, and virulence.
    Keywords:
    DRUG RESISTANCE, MICROBIALEXPERIMENTAL LAB STUDYMICEPENICILLIN GPRECIPITIN TESTSSTREPTOCOCCAL INFECTIONSSTREPTOCOCCUS PYOGENES

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