Abstract
Staphylococcus pseudintermedius is an opportunistic and emerging zoonotic pathogen that primarily colonises the skin of dogs. Many common variants are methicillin resistant (MRSP) or multidrug resistant (MDR), and drug resistance is increasingly reported across the globe. In New Zealand, MRSP isolation remains rare in clinics. To pre-emptively inform diagnostic and antimicrobial stewardship practices, we examine isolates of S. pseudintermedius, MRSP and MDR-MRSP from New Zealand dogs using a combination of methodologies. Genetic and genomic data combined with antimicrobial susceptibility screening identify common drug-resistance profiles and their genetic determinants. We demonstrate that sensitive and specific species-level identification of S. pseudintermedius can be achieved using Bruker MALDI-TOF MS and, further, that this technique can be used to identify some common subtype variants, providing a level of categorical precision that falls somewhere between single-locus and multi-locus sequence typing. Comparative genomics analysis of global S. pseudintermedius data shows that MRSP moves frequently across the globe, but that horizontal gene transfer events resulting in the acquisition of the SCCmec cassette (responsible for beta-lactam antibiotic resistance) are infrequent. This suggests that biosecurity and surveillance in addition to antibiotic stewardship should play important roles in mitigating the risk of MRSP, especially in countries such as New Zealand where MRSP is still rare.
Highlights
Staphylococci are ubiquitous gram-positive bacteria, of which many are opportunistic pathogens that commonly constitute part of the natural skin flora of diverse animal species[1,2]
Isolates were tested for novobiocin, polymyxin B and acriflavine sensitivities which have been shown to discriminate between coagulase positive/negative staphylococci or between S. aureus and members of the SIG43
MALDI-TOF identification is a valuable tool for diagnostic laboratories, there are mixed reports in the literature about the specificity of MALDI-TOF typing for the identification of S. pseudintermedius[20,21,22]
Summary
Staphylococci are ubiquitous gram-positive bacteria, of which many are opportunistic pathogens that commonly constitute part of the natural skin flora of diverse animal species[1,2]. In veterinary medicine, where the use of important human antimicrobials such as vancomycin, daptomycin and linezolid is increasingly discouraged (eg.14), this effectively renders some of these lineages extensively, or pan-drug resistant (XDR, PDR) to their recommended and available antibiotics. These variants are commonly carried on the skin and oral mucus membranes of healthy animals, and no effective strategy exists for the removal of commensal association[13] leaving surveillance and monitoring as the only effective approaches to reduce the burden of antimicrobial resistance[15]. Using WGS-derived phylogenies we demonstrate that acquisition of the SCCmec cassette by horizontal gene transfer has occurred less frequently than has previously been estimated and that this difference in estimation is due to limitations in the phylogenetic resolution provided by seven gene MLST data
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