Canine otic rinse product inhibits the growth of resistant MRSP bacteria, claims a new research.

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is a common bacterium in canine ear and skin infections. Based on laboratory trials, the antimicrobial effect of a resin-based otic rinse product on MRSP bacteria is significant.

The significant antimicrobial effect of a canine otic rinse product on methicillin-resistant Staphylococcus pseudintermedius (MRSP) bacteria has recently been demonstrated in a laboratory trial. Staphylococcus pseudintermedius is a common bacterium in canine ear and skin infections. The Finnish resin-based canine otic rinse product was developed for cleaning dogs’ ears, as well as for general management of otitis externa.

The amount of viable bacterial cells decreased significantly in 24 hours

Three of the major MRSP strains circulating in the Finnish dog population were tested.
“Each bacteria was exposed to the resin-based otic rinse solution for 24 hours. The product showed a strong antimicrobial effect against the MRSP strains: viable bacterial cell counts collapsed,” explained veterinarian Elina Aimo-Koivisto from the Faculty of Veterinary Medicine, University of Helsinki. Aimo-Koivisto presented these results at the Annual Finnish Veterinary Congress.

“Changes in bacterial cell morphology were already evident in electron microscopy images after six hours of resin exposure. Vacuolization of the cells was common, and in some cells, the structure was completely destroyed,” Aimo-Koivisto continues.

Further research on resin-based otic rinse solution is warranted

The prudent use guidelines in Finland were implemented for veterinarians to minimize the use of antimicrobial agents in canine otitis externa treatment. Several factors, such as atopy or allergy, predispose dogs to this condition. Otic rinse products are used for cleaning canine ears, and also for general management of otitis externa.
“Based on this laboratory trial, the antimicrobial effect of this resin-based otic rinse product on MRSP bacteria is significant. We are currently investigating the effect of this product on other bacterial species. Our wish is to conduct a clinical trial to explore the product’s benefit in the treatment of canine otitis externa,” says the study’s supervisor, docent Merja Rantala.


Collaborators: Repolar Pharmaceuticals Oy, Finnsusp Oy Laboratoriopalvelut. The research has been supported by the Finnish Foundation of Veterinary Research.

Did you know?



•    Homemade resin salves of coniferous trees, such as Norway spruce (Picea abies), have been used for centuries to treat infected wounds
•    Resin contains many components, including p-coumaric acid, rosin acids, and lignans
•    Scientific studies have investigated the antimicrobial effects of various resin components
•    There is scientific evidence for the efficacy of resin salve in treating chronic wounds also in humans
•    This study tested a previously developed Finnish resin-based otic rinse solution for canine ear cleaning

Canine otitis externa

•    Canine otitis externa is a common and often recurrent condition
•    Animals suffering from recurrent otitis usually have predisposing conditions, such as atopy or allergies
•    The use of antimicrobial agents in treating otitis externa is controversial due to poor treatment responses and increasing antimicrobial resistance
•    Treatment of the localized  symptoms as well as the underlying cause are important in managing otitis externa
•    If your dog has symptoms of otitis externa, it is important to consult a veterinarian early in the disease course, before the condition becomes chronic