New information about the epidemiology of MRSP in Finland

The population of MRSP bacteria (methicillin resistant Staphylococcus pseudintermedius) in Finland has become genetically very diverse in just a few years, as demonstrated by a new study published in the Journal of Antimicrobial Chemotherapy.

The study was conducted at the Clinical microbiology laboratory of the Faculty of Veterinary Medicine, and covered nearly 2,000 strains of the bacterium. The study was funded by the Alfred Kordelin Foundation and the Helvi Knuuttila Fund.

MRSP evolves rapidly

“In 2010-2011, when people became aware of the problems caused by MRSP, the bacterium was spreading largely through bacterial clones, i.e. bacteria which were nearly identical in genetic terms. At that time, the most important clone was the sequence type 71 (ST71), which was also common elsewhere in Europe. A few years later, the number of different bacterial clones was significantly larger,” says LicVetMed Thomas Grönthal, who is working on his dissertation on the epidemiology of the bacterium. “By studying the genetics of the bacterial strains it was established that its genome had become more diverse. This indicates rapid evolution, i.e., gene transfer between strains, which also effectively transfers the genes that convey resistance to antibiotics,” he continues. The bacterium has spread throughout Finland. MRSP bacteria are usually multiresistant, so treating infections caused by them is challenging. The sensitive form of the bacterium is part of the normal microbiota of dogs and, to a lesser degree, cats. However, the study concluded that cats are not a significant source for MRSP.

Antibiotic resistance is common

The study also examined the sensitivity of Staphylococcus pseudintermedius to antibiotics in general. According to head of laboratory, DrVetMed Merja Rantala, the resistance figures are worrying.  “Almost one in seven bacterial strains (14%) was resistant to methicillin, meaning that treatment with penicillin derivatives or cephalosporins is ineffective. These are important antibiotics commonly used on small animals,” she says. “What is even more worrying is that resistance towards alternative antibiotics, such as macrolides, lincosamides and tetracycline was between 30% and 40%, so treatment options are becoming fewer and fewer,” she maintains.

Like many previous studies, the results also showed a link between antibiotic treatment and antibiotic resistance. Ongoing antibiotic treatment during testing was a significant risk factor for an S. pseudintermedius isolate being MRSP. Veterinarians, pet owners and breeders must all cooperate to improve the antibiotic resistance situation. “In practice this means that we must dramatically reduce the use of antibiotics and favour other forms of treatment whenever possible. We should invest in animal health care. Breeding can also be used to get healthier animals,” Grönthal specifies.

Prevalence of MRSP

The study also offered a rough estimate of the prevalence of MRSP. Approximately 3% of dogs from which bacteriological specimens were taken had MRSP. Among dogs with risk factors (skin infections, a history of many antibiotic treatments), MRSP was three times as common. Among cats, MRSP was very rare. “These results give us an indication of the prevalence of MRSP in the animal population, but we need further research to confirm the data,” states Rantala.

Antimicrobial resistance in Staphylococcus pseudintermedius and the molecular epidemiology of methicillin-resistant S. pseudintermedius in small animals in Finland