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Published on: September 3, 2016

Effects of subminimal inhibitory concentrations of antibiotics in experimental infections

O Zak, F Kradolfer

    Reviews of Infectious Diseases
    |September 1, 1979
    PubMed

    Insights

    Sub-minimal inhibitory concentrations (sub-MICs) of antibiotics showed varied antibacterial effects. While some antibiotics at sub-MICs aided survival in certain gram-negative infections, others were ineffective or even detrimental.

    Area of Science:

    • Microbiology
    • Pharmacology
    • Infectious Diseases

    Background:

    • Antibiotic efficacy is typically assessed at or above minimal inhibitory concentrations (MICs).
    • The impact of sub-MIC antibiotic exposure on bacterial pathogens and host outcomes is less understood.
    • Sub-MIC antibiotic effects can include alterations in bacterial morphology and virulence.

    Purpose of the Study:

    • To investigate the antibacterial effects of sub-MIC antibiotic concentrations in animal models.
    • To evaluate the impact of sub-MIC antibiotic treatment on bacterial growth and host survival.
    • To compare the efficacy of different antibiotics at sub-MIC levels against various bacterial infections.

    Main Methods:

    • Two animal models were utilized: mice and rabbits.
    • Antibiotics tested included cephalosporins (CGP 9000, cephalexin, cephaloridine), ampicillin, and gentamicin.
    • Sub-MICs were administered orally or intravenously, with drug concentrations measured relative to the MIC.

    Main Results:

    • In mice, oral cephalosporins at sub-MICs were effective against some gram-negative infections but not gram-positive ones.
    • In rabbits, sub-MIC beta-lactam antibiotics induced bacterial filamentation, and gentamicin caused enlargement of Proteus mirabilis, Escherichia coli, and Salmonella typhimurium.
    • Sub-MIC treatment prolonged survival in E. coli and P. mirabilis infections but shortened survival in S. typhimurium infections.

    Conclusions:

    • Sub-MIC antibiotic concentrations can exhibit complex and sometimes paradoxical effects on bacterial infections.
    • The outcome of sub-MIC antibiotic treatment is dependent on the specific antibiotic, bacterial species, and infection model.
    • Further research is needed to fully elucidate the clinical implications of sub-MIC antibiotic exposure.

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