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Published on: November 4, 2016
High genotypic diversity among methicillin-resistant Staphylococcus pseudintermedius isolated from canine infections
Peter Damborg1, Arshnee Moodley2, Bent Aalbæk2
1Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, 1870, Frederiksberg C, Denmark. pedam@sund.ku.dk.
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.
Insights
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) in Danish dogs shows high genetic diversity, with ST71 being common and multidrug-resistant. Newer CC258 clones, however, exhibit greater susceptibility to tested antibiotics.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Resistance
- Companion Animal Health
Background:
- Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is a growing global concern in companion animals.
- The multidrug-resistant ST71 clone has been prevalent in Europe, but emerging MRSP clones are being identified.
- Understanding MRSP genotypic diversity and antimicrobial resistance in canine populations is crucial for effective treatment and control.
Purpose of the Study:
- To investigate the genotypic diversity of clinical MRSP isolates from dogs in Denmark.
- To determine the antimicrobial resistance profiles of these MRSP isolates.
- To analyze the evolution and spread of MRSP clones in a canine population over a six-year period.
Main Methods:
- Antimicrobial susceptibility testing was performed on 46 clinical MRSP isolates from 36 dogs (2009-2014).
- Multilocus-sequence typing (MLST) and SCCmec typing were employed to characterize MRSP isolates.
- Isolates were analyzed for sequence types (STs), clonal complexes (CCs), and resistance patterns.
Main Results:
- Twenty-three different STs were identified, with ST71 (SCCmec II-III) being the most common (13 dogs).
- A significant proportion of isolates belonged to CC258 (ST258-SCCmec IV) and its variants (19 isolates).
- CC258 isolates showed broader susceptibility to antibiotics compared to the multidrug-resistant CC71 isolates, particularly for fluoroquinolones and aminoglycosides.
Conclusions:
- MRSP in Denmark exhibits high genotypic diversity, suggesting multiple introductions of mobile genetic elements and rapid evolution.
- While ST71-SCCmec II-III remains the dominant multidrug-resistant lineage, CC258-SCCmec IV represents a newer clone with increased antimicrobial susceptibility.
- Distinct STs isolated from the same dog over time indicate potential for repeated exposure or in-host MRSP evolution.
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