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Introduction: In recent years, the methicillin-resistance encoding gene mecA has been identified among coagulase-negative staphylococci (CNS) like Staphylococcus fleurettii, Staphylococcus vitulinus and further CNS. In 2011, a novel mecA homologue (mecC; EMBL FR821779) harbored by SCCmecXI was described for methicillin reistant Staphylococcus aureus (MRSA) from human and bovine origin, and later also from wildlife, companion animals as well as environmental sites including water.
Objectives: To gain deeper insights into the genomic region downstream of the chromosomal integration site (attBSCC) of the mecC-positive S. stepanovicii, we conducted whole genome
Materials & Methods: The Staphylococcus stepanovicii strain IMT27065 (ODD4) was isolated in August 2011 from a fecal sample of a wild bank vole (Myodes glareolus) as part of a screening study focusing pathogens from wild rodents (Network “Rodent-Borne Pathogens”). Whole genome sequencing was carried out on a HiSeq (Illumina, USA). The reads were assembled using CLC Genomics Workbench 7.5 (CLC bio, Denmark) and open reading frames (ORFs) were predicted using Prodigal. Annotation of ORFs and prediction of (protein) coding sequences (CDS) was performed by The RAST Server. Putative CDS function and conserved domains were predicted with blastn and blastx using the NCBI database. For comparative genomic analyses Geneious 7.1.5 was employed.
Results and Discussion: Here we report on the entire nucleotide sequence of the region between the rRNA-methyltransferase (orfX)-like gene and the tRNA dihydrouridine synthase B (orfY)- like gene in a mecC-positive strain (IMT28705, GenBank accession no. KR732654). Genome sequencing revealed that the isolate harbors a mecC gene which shares 99.2% nucleotide (and 98.5% amino acid) sequence identity with mecC from S. aureus strain LGA251. In addition, the mecC encoding region harbors the typical blaZ-mecC-mecR1-mecI structure (5,163 bp), corresponding with the class E mec complex. A similar structure (including mecB instead of mecC) was reported for Macrococcus caseolyticus, either as part of a transposon located on plasmids or within an SCCmec element. However, the region between the orfX and orfY-like genes seems to lack transposases as well as ccr recombinase homologues. One the other hand, analysis of the 15bp direct repeats (DR) flanking attBSCC revealed similar DRs widely distributed downstream of orfX within the genus taphylococcus, especially within SCCmec elements of MRSA, indicating the possibility of a broad genetic exchange.