Structural Polymorphism of Genome Islands Encoding Resistance to Beta-Lactams in Coagulase-Negative Staphylococci Isolated at Hospitals of the Russian Federation

Coagulase-negative staphylococci (CoNS) are considered as a reservoir of mobile genetic elements and first of all of the staphylococcal cassette chromosome mec (SCCmec), defining staphylococci resistance to beta-lactams. Types II, IV, IVa, V, VII and VIII SCCmec were detected among 95 staphylococcal strains isolated in different regions of the Russian Federation. Subtypes Cla, Clb, Clc and Cl SCCmec were also identified (class B mec complex and two complexes of ccrl and ccr2 genes recombinases). Some other cassette types carrying A, C1 and C2 classes of the mec complexes in combination with various recombinase genes were detected. The S.epidermidis isolates mainly formed cassettes carrying mec complex B, while the S.haemolyticus isolates had cassettes carrying classes C1 and C2 mec complex. Out of 9 isolates of S.hominis 5 isolates carried a new type cassette: class A mec complex in combination with the complex of the recombinase ccrl genes. SCCmec was not identified in S.capitis and S.pasteuri. Their representatives carried either mec complex (1 isolate of S.pasteuri) or the recombinase complexes (2 isolates of S.capitis). The detected SCCmec variants in CoNS could be a source of emergence of new genetic lines of MRSA.