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Updated: Jun 9, 2025
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Published on: November 4, 2016
Genomic Analyses of Methicillin-Resistant Staphylococcus pseudintermedius from Companion Animals Reveal Changing
Mattias Myrenås1, Karl Pedersen2, Ulrika Windahl1
1Swedish Veterinary Agency, Ulls väg 2b, SE-75189 Uppsala, Sweden.
Background/Objectives:
Staphylococcus pseudintermedius is part of the normal microbiota in dogs. Since 2006, an increase in multidrug-resistant clones of methicillin-resistant S. pseudintermedius has been reported, as well as zoonotic transmission. Longitudinal investigations into clonal population structures, antibiotic resistance patterns, and the presence of resistance and virulence genes are important tools for gaining knowledge of the mechanisms behind the emergence of such clones.
Methods:
We investigated 87% of all non-repetitive MRSP isolates from dogs and cats in Sweden over a ten-year period (n = 356). All isolates were subjected to staphylococcal chromosomal cassette mec identification, whole-genome sequencing, multi-locus sequence typing, and analyses of genomic relatedness, as well as investigation of phenotypical resistance patterns and the presence of antibiotic resistance genes and virulence genes.
Results:
A considerable increase over time in the number of clonal lineages present was observed, indicating genomic diversification, and four clones became dominant: ST71, ST258, ST265, and ST551. In total, 96% of the isolates were multidrug-resistant. Statistically significant differences in resistance to several antibiotic classes between the four dominant clones were present. All isolates carried several virulence genes encoding factors associated with attachment, colonization, toxin synthesis, quorum sensing, antibiotic resistance, and immune evasion.
Insights
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs has diversified into dominant clones, with 96% exhibiting multidrug resistance. This study tracked MRSP evolution over ten years, revealing concerning trends in antibiotic resistance and virulence.
Area of Science:
- Veterinary Microbiology
- Genomics
- Antimicrobial Resistance
Background:
- Staphylococcus pseudintermedius is a common canine commensal.
- Since 2006, methicillin-resistant S. pseudintermedius (MRSP) has increased, with documented zoonotic potential.
- Understanding MRSP clonal evolution and resistance mechanisms is crucial.
Purpose of the Study:
- To investigate the population structure, genomic relatedness, and antibiotic resistance patterns of MRSP isolates from dogs and cats in Sweden over a decade.
- To identify dominant MRSP clones and analyze their associated resistance and virulence genes.
Main Methods:
- Analysis of 356 non-repetitive MRSP isolates collected over ten years.
- Whole-genome sequencing, multi-locus sequence typing, and identification of staphylococcal chromosomal cassette mec.
- Phenotypic resistance testing and genomic analysis of resistance and virulence genes.
Main Results:
- Genomic diversification observed, with four clones (ST71, ST258, ST265, ST551) becoming dominant.
- 96% of isolates displayed multidrug resistance, with significant variations between dominant clones.
- All isolates possessed virulence genes linked to attachment, colonization, toxin production, and immune evasion.
Conclusions:
- MRSP in Sweden has undergone significant clonal diversification and genomic evolution over ten years.
- Dominant MRSP clones exhibit high rates of multidrug resistance and carry a range of virulence factors.
- Longitudinal genomic surveillance is essential for monitoring the emergence and spread of resistant pathogens like MRSP.
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