Whole genome sequencing of methicillin-resistant and methicillin-sensitiveisolated from 4 horses in a veterinary teaching hospital and its ambulatory service.

Abstract

Genomic characterization was conducted on 2 methicillin-resistant(MRSA) strains isolated from 2 horses hospitalized during an overlapping period of time and 2 methicillin-sensitive(MSSA) strains isolated from 2 distinct horses. Phylogenetic proximity was traced and the genotypic and phenotypic characteristics of the antimicrobial resistance of the strains were compared. Whole genome sequencing of MRSA strains for this report was similar but differed from whole genome sequencing of MSSA strains. The MRSA strains were closely related, belonging to sequence type (ST) 612,type t1257, and SCCtype IVd2B. The MSSA strains were also closely related, belonging to ST1660,type t3043, and having no detectable staphylococcal cassette chromosomeelements. All MSRA and MSSA strains were Panton-Valentine leukocidin negative. There were discrepancies in the genotypic analysis and the antimicrobial susceptibility testing (phenotypic analysis) of MRSA strains for rifampin, trimethoprim-sulfamethoxazole, gentamicin, amikacin, and enrofloxacin.