title: High genotypic diversity among methicillin-resistant Staphylococcus pseudintermedius isolated from canine infections in Denmark.
abstract: BACKGROUND
  Methicillin-resistant Staphylococcus pseudintermedius (MRSP) has emerged globally in companion animals in the last decade. In Europe, the multidrug-resistant sequence type (ST)71 is widespread, but recently other clones have appeared. The objective of this study was to examine genotypic diversity and antimicrobial resistance of clinical MRSP isolates obtained from dogs, including dogs sampled on multiple occasions, in Denmark over a six-year period. For that purpose a total of 46 clinical MRSP isolates obtained from 36 dogs between 2009 and 2014 were subjected to antimicrobial susceptibility testing, multilocus-sequence typing (MLST) and SCCmec typing.
  
  
  RESULTS
  Twenty-three sequence types were identified with ST71, mostly associated with SCCmec II-III, as the most common occurring in 13 dogs. Among the remaining 33 isolates, 19 belonged to clonal complex (CC)258 comprising ST258-SCCmec IV and its single- and double-locus variants. These were susceptible to 4-7 of the 22 antibiotics tested, whereas CC71 isolates were susceptible to only 2-5 antibiotics. Clone-specific differences were especially pronounced for fluoroquinolones and aminoglycosides with most CC71 isolates being resistant and almost all CC258 isolates being susceptible. Sixteen of the 19 CC258 isolates had oxacillin MICs of 0.5 g/L, whereas MICs for CC71 isolates were consistently above 4 g/L. Four of five dogs representing multiple isolates had distinct STs on different sampling events.
  
  
  CONCLUSIONS
  The overall genotypic diversity of MRSP is high in Denmark indicating multiple acquisitions of SCCmec into distinct clones, and mutational evolution, which appears to be particularly rapid for certain ancestral clones such as ST258. ST71-SCCmec II-III is the most common MRSP lineage and is typically multidrug-resistant. CC258-SCCmec IV isolates, which emerged in Denmark since 2012, display susceptibility to a wider range of antimicrobials. The isolation of distinct STs in individual dogs over time suggests repeated exposure or short-term genetic evolution of MRSP clones within patients.
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark. pedam@sund.ku.dk.
authors.forename: Peter
authors.initials: P
authors.lastname: Damborg
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.
authors.forename: Arshnee
authors.initials: A
authors.lastname: Moodley
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.
authors.forename: Bent
authors.initials: B
authors.lastname: Aalbæk
authors.affiliation: Department of Veterinary Medicine, Università degli Studi di Bari, Strada P.le per Casamassima Km 3, Valenzano-Bari, 70010, Italy.
authors.forename: Gianpiero
authors.initials: G
authors.lastname: Ventrella
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.
authors.forename: Teresa Pires
authors.initials: TP
authors.lastname: Dos Santos
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark.|Department of Biomedical Sciences, Ross University School of Veterinary Medicine, Basseterre, West Indies, St Kitts and Nevis.
authors.forename: Luca
authors.initials: L
authors.lastname: Guardabassi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003718:Denmark; D004283:Dog Diseases / Q000382:microbiology*; D004285:Dogs; D014644:Genetic Variation; D005838:Genotype; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000382:microbiology / Q000662:veterinary*; D013210:Staphylococcus / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents
keywords: Antibiotic resistance; Dog; MRSP; Multilocus sequence typing; ST258; ST71