Methicillin-resistant Staphylococcus aureus outbreak in a Dutch equine referral clinic

In 2020 and 2022 nine cases of surgical site infections (SSI) in horses in an equine referral clinic were diagnosed with a methicillin-resistant Staphylococcus aureus (MRSA) infection. Molecular characterization of 16 MRSA isolates originating from two putative outbreaks of SSIs in 2020 and 2022 in an equine referral clinic showed that the isolates belonged to three different clusters. In 2020 ST398 was found in five SSIs and one staff member suggesting nosocomial transmission. Despite the fact that another staff member (H1) also carried MRSA ST398, this isolate was not related and could therefore be considered as a separate introduction. In 2022, nine isolates from four SSIs, two staff members and three environmental samples were divided into two distinct clusters, ST398 and ST612. Within the clusters nosocomial transmission is likely. ST398 was found in 2020 and in 2022, but both clusters were not related and belonged to different spa-types.