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Increased resistance to chloramphenicol in Rickettsia prowazekii with a note on failure to demonstrate genetic

E WEISS, H R DRESSLER

    Journal of Bacteriology
    |February 1, 1962
    PubMed

    Insights

    Researchers developed a chloramphenicol-resistant Rickettsia prowazekii strain through serial passage in eggs. This new strain showed cross-resistance to thiocymetin but not other drugs, and genetic interaction attempts failed.

    Area of Science:

    • Microbiology
    • Bacteriology
    • Genetics

    Background:

    • Rickettsia prowazekii is an important human pathogen.
    • Understanding antibiotic resistance mechanisms in Rickettsia is crucial for treatment.
    • Previous efforts to genetically label Rickettsia strains were limited.

    Purpose of the Study:

    • To develop a chloramphenicol-resistant strain of Rickettsia prowazekii.
    • To investigate the genetic stability of induced antibiotic resistance.
    • To explore potential genetic interactions among Rickettsia strains with different resistance profiles.

    Main Methods:

    • Serial passage of Rickettsia prowazekii (Madrid E strain) in embryonated eggs with increasing chloramphenicol concentrations.
    • Isolation and characterization of a chloramphenicol-resistant substrain (C(r)).
    • Testing for cross-resistance to other antibiotics and genetic interaction assays in eggs and cell cultures.

    Main Results:

    • A chloramphenicol-resistant Rickettsia prowazekii substrain, C(r), was successfully isolated after 40 serial passages.
    • The C(r) strain exhibited a two-step increase in chloramphenicol resistance, which was stable over 10 drugless passages.
    • Cross-resistance to thiocymetin was observed, but not to unrelated drugs. Attempts to demonstrate genetic interaction among resistant strains were unsuccessful.

    Conclusions:

    • Antibiotic resistance can be induced in Rickettsia prowazekii through serial passage.
    • The induced chloramphenicol resistance is genetically stable.
    • Genetic interaction or recombination among Rickettsia strains with different resistance markers could not be demonstrated under the tested conditions.
    Keywords:
    CHLORAMPHENICOL/pharmacologyRICKETTSIA/pharmacology

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