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The pleiotropic effect of spontaneous single-step variant production in Mycobacterium intracellulare

R Kajioka, J Hui

    Scandinavian Journal of Respiratory Diseases
    |April 1, 1978
    PubMed

    Insights

    Opaque colony variants of Mycobacterium intracellulare exhibit enhanced permeability due to cell envelope alterations. This increased permeability affects antibiotic susceptibility and nutrient utilization, impacting bacterial virulence.

    Area of Science:

    • Microbiology
    • Bacterial genetics
    • Cell envelope studies

    Background:

    • Mycobacterium intracellulare is an opportunistic pathogen.
    • Colony morphology can indicate genetic or physiological changes in bacteria.
    • Cell envelope properties influence bacterial behavior and drug resistance.

    Purpose of the Study:

    • To investigate the characteristics of transparent and opaque colony forms of Mycobacterium intracellulare AT 13786.
    • To determine if the opaque form is a mutant and understand the underlying mechanisms of its altered properties.
    • To assess the implications of these changes on antibiotic susceptibility, growth, and virulence.

    Main Methods:

    • Isolation and cloning of transparent and opaque colony forms from M. intracellulare AT 13786.
    • Comparative analysis of growth rates in standard media.
    • Assessment of tween dependence for dextrose utilization.
    • Evaluation of susceptibility to various antibiotics.
    • Investigation of cell envelope permeability differences.

    Main Results:

    • The opaque colony form was identified as a mutant of the transparent type.
    • Opaque variants showed enhanced cell envelope permeability.
    • Opaque M. intracellulare exhibited increased susceptibility to several antibiotics.
    • The opaque form demonstrated faster growth and loss of tween dependence for dextrose utilization.
    • Similar alterations were observed in an avirulent opaque colony form of pathogenic strain serotype Boone.

    Conclusions:

    • Cell envelope alterations in the opaque M. intracellulare mutant lead to enhanced permeability.
    • These permeability changes correlate with altered antibiotic susceptibility and nutrient metabolism.
    • The observed changes may have significant implications for understanding the virulence of Mycobacterium intracellulare.

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