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[Genetic environments of bla(CTX-M) genes located on conjugative plasmids of Enterobacteriaceae nosocomial isolates

N K Fursova, S D Pryamchuk, I V Abaev

    Antibiotiki I Khimioterapiia = Antibiotics and Chemoterapy [Sic]
    |May 18, 2011
    PubMed

    Insights

    The bla(CTX-M) gene, conferring cephalosporin resistance in Enterobacteriaceae, was found in 71% of hospital isolates. These resistance genes are often located on mobile plasmids and associated with mobile genetic elements like ISEcp1.

    Area of Science:

    • Microbiology
    • Genetics
    • Molecular Biology

    Background:

    • Cephalosporin resistance in Enterobacteriaceae is a growing public health concern.
    • The bla(CTX-M) gene is a major mechanism of this resistance.
    • Understanding the genetic basis and dissemination of bla(CTX-M) is crucial for infection control.

    Purpose of the Study:

    • To investigate the prevalence and genetic characteristics of bla(CTX-M) genes in Enterobacteriaceae nosocomial isolates.
    • To identify the specific bla(CTX-M) subtypes and their associated mobile genetic elements.
    • To determine the plasmid location and gene environments of these resistance genes.

    Main Methods:

    • Genomic analysis of 833 Enterobacteriaceae nosocomial isolates collected from Russian hospitals (2003-2007).
    • Identification of bla(CTX-M) gene subtypes using molecular methods.
    • Plasmid analysis to determine incompatibility groups and location of bla(CTX-M) genes.
    • Investigation of upstream and downstream genetic elements, including insertion sequences and mobile genetic elements.

    Main Results:

    • bla(CTX-M) genes were detected in 71% of cephalosporin-resistant Enterobacteriaceae isolates.
    • bla(CTX-M-15) was the most prevalent subtype, followed by bla(CTX-M-14), bla(CTX-M-3), and others.
    • Genes were located on conjugative plasmids (IncF, IncL/M, IncA/C, IncI1-ly).
    • Specific mobile genetic elements, notably ISEcp1, were found upstream of several bla(CTX-M) subtypes, with characteristic spacer sequences.
    • Downstream sequences included orf477, mucA, and IS903, with bla(CTX-M-2) and bla(CTX-M-9) located within ISCR1.

    Conclusions:

    • bla(CTX-M) genes are highly prevalent in Russian hospital-acquired Enterobacteriaceae infections.
    • The genetic context and plasmid location of bla(CTX-M) genes facilitate their spread.
    • Specific mobile genetic elements play a significant role in the mobilization and expression of bla(CTX-M) genes.

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