Comparative Genomics and Drug Resistance of a Geographic Variant of ST239 Methicillin-Resistant <em>Staphylococcus aureus</em> Emerged in Russia

<div><p>Two distinct classes of methicillin-resistant <em>Staphylococcus aureus</em> (MRSA) are spreading in hospitals (as hospital-acquired MRSA, HA-MRSA) and in the community (as community-acquired MRSA, CA-MRSA). Multilocus sequence type (ST) 239 MRSA, one of the most worldwide-disseminated lineages, has been noted as a representative HA-MRSA. Here, we isolated ST239 MRSA (<em>spa</em> type 3 [t037] and staphylococcal cassette chromosome <em>mec</em> [SCC<em>mec</em>] type III.1.1.1) and its novel variant with ST239/<em>spa</em>351 (t030)/SCC<em>mec</em>III.1.1.4 (SCC<em>mec</em>III_R) not only from hospitals but also from patients with urethritis in the community in Russia. The Russian variant (strain 16K) possessed a hybrid genome consisting of CC8 and CC30, similar to the ST239/<em>spa</em>3/SCC<em>mec</em>III.1.1.1 HA-MRSA (TW20) genome, but with marked diversity. The 16K′ CC30 section had SCC<em>mec</em>III_R carrying the <em>dcs</em>-carrying unit (which corresponded to the SCC<em>mec</em>IVc J3 joining region of ST30 CA-MRSA), lacked SCCmercury, and possessed a novel mobile element structure (MES16K) carrying the <em>ccrC</em>-carrying unit (with the recombinase gene <em>ccrC1</em> allele 3) and drug resistance tranposons. The Russian variant included strains with a high ability to transfer its multiple drug resistance by conjugation; e.g., for strain 16K, the transfer frequency of a chloramphenicol resistance plasmid (p16K-1 with 2.9 kb in size) reached 1.4×10⁻², followed by Tn<em>554</em> conjugative transfer at 3.6×l0⁻⁴. The Russian variant, which has been increasing recently, included divergent strains with different plasmid patterns and pulsed field gel electrophoresis profiles. The data demonstrate the alternative nature of ST239 MRSA as CA-MRSA and also as a drug resistance disseminator, and its micro but dynamic evolution in Russia.</p>