The clonal diversity and antimicrobial resistance of methicillin resistant Staphylococcus pseudintermedius

The characterization of essential MRSP strains is an important step in the development of alternative therapeutics. MRSP strains in the United States were previously characterized using Multilocus Sequence Typing (MLST) and Based Upon Related Sequence Types (BURST) analysis. This study however lacked whole genome sequencing (WGS) to distinguish antimicrobial resistance and virulence genes between the MRSP strains. To characterize MRSP isolates from dogs in the United States, we have used antimicrobial susceptibility, WGS, MLST, geoBURST, antimicrobial resistant genes, virulence genes, and phylogenetic analysis. Using similar methods, we have also reported on the prevalence and molecular epidemiology of MRSP in South Africa. Staphylococcus pseudintermedius is being reported more frequently in humans. Hence, we have performed the characterization of S. pseudintermedius of human origin compared to canine origin. The initial results were the detection of new clonal lineages and antibiotic resistance of MRSP in the United States. Secondly, phylogenetic analysis, recombination, and positive selection of the MLST data showed that MRSP lineages currently circulating in the United States do not share a common ancestor with isolates reported 10 years ago. The antimicrobial resistance of S. pseudintermedius isolated from dogs has also increased over the past ten years. The molecular epidemiology of S. pseudintermedius among dogs isolates from South Africa showed a high prevalence of MRSP and a non-clonal population structure. High antimicrobial susceptibility and a non-clonal population structure of S. pseudintermedius were observed among human isolates compared to canine isolates. Finally, the study suggests that the bla regulators are important in the control of oxacillin-resistant phenotype in S. pseudintermedius. As a result of this dissertation, there are interesting epidemiological implications regarding the evolution and host adaptability of MRSP around the world, which may impact the treatment of MRSP infections and development of alternative therapeutics in the future.