Comparative molecular analysis substantiates a zoonotic potential of equine Methicillin- resistant Staphylococcus aureus (MRSA) -- Walther et al., 10.1128/JCM.01626-08 -- Journal of Clinical Microbiology.
Despite the increasing importance of Methicillin-resistant Staphylococcus aureus (MRSA) in veterinary medicine, knowledge about the epidemiology of these pathogens in horses is still poor. The phylogenetic relationship of strains from human and equine origin has been addressed before, usually by analyzing results of common standard classification methods for MRSA. This work intends to go beyond the base line of typing procedures in order to comparatively characterize equine and human MRSA strains of similar phylogenetic background. Additionally to MLST, PFGE, spa typing, SCCmec typing and a PCR for PVL detection, a microarray analysis of altogether 185 structural, virulence-associated and resistance loci was applied. As a result, the clonal complex (CC) 8 was absolutely predominant (16) in 19 investigated equine MSRA strains. Of CC8, 13 strains belonged to sequence type (ST) 254, three others to ST8. This genotype has been isolated from different equine patients in various regions over several years, substantiating the apparent predominance of CC8 STs in MRSA strains of horses worldwide. Beyond that, comparatively investigated human strains of ST254 displayed indistinguishable molecular typing results to those of equine origin. Two further equine strains (ST22, ST1117) showed similarity to ST22 human strains (CC22). One equine strain was of ST398, a genotype recently described to be frequently isolated from specimens of pigs and pig farmers. These data provide evidence for the adaptation to more than one mammalian species of certain MRSA genotypes, reflecting their extended host spectrum.
