Emergence of Novel Methicillin-Resistant Staphylococcus pseudintermedius Lineages in Scotland: Insights from Whole Genome Sequencing

In a groundbreaking study, researchers have uncovered the emergence of novel methicillin-resistant Staphylococcus pseudintermedius (MRSP) lineages in Scotland, using whole genome sequencing of isolates from both companion animals and humans. Staphylococcus pseudintermedius, an opportunistic pathogen predominantly found in dogs, is increasingly being detected in humans, often through direct contact with dogs.

The study, which spans from 2007 to 2020, involved retrospective genotyping and antimicrobial susceptibility testing of 406 S. pseudintermedius isolates. These isolates were collected from a variety of hosts, including dogs, cats, an otter, and humans across Scotland. A total of 75 sequence types (STs) were identified among the 130 genotyped isolates, with 59 of these types observed only once.

Significantly, the researchers noted the emergence of two MRSP clones in Scotland: ST726, a novel clone evolving locally, and ST551, which was first reported in Poland in 2015 and may be linked to the importation of animals from Central Europe to Scotland. Although ST71 remains the most frequently detected S. pseudintermedius strain, other lineages, which have begun replacing ST71 in other countries, were also identified, including ST551.

The study's findings highlight the pressing issue of multidrug resistance (MDR) in MRSP, with 96.4% of MRSP and 8.4% of methicillin-susceptible S. pseudintermedius (MSSP) isolates showing MDR. Notably, one MRSP isolate exhibited resistance to mupirocin, an antibiotic commonly used to treat skin infections.

These results underscore the need for continuous surveillance to monitor the emergence and spread of novel MDR MRSP lineages in both animals and humans. Understanding changes in antimicrobial susceptibility in S. pseudintermedius is crucial for minimizing the threat to animal and human health.

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