Methicillin-resistant staphylococci (MRS) are increasingly being isolated in bovine mastitis. The aim of our study was to evaluate the occurrence of MRS in Finnish mastitis milk samples and characterize the MRS isolates using molecular methods.

Nationwide surveillance identified 10 human isolates of methicillin-resistant Staphylococcus aureus clonal complex (CC) 398. Further typing in comparison with animal isolates identified 4 clusters: 1 related to a horse epidemic and 3 to persons who had no direct contact with animals or each other. These findings may indicate unrecognized community transmission.

Methicillin-resistant Staphylococcus aureus (MRSA) carrying mecC gene (mecC-MRSA) is frequently reported among European hedgehogs (Europeaus erineaus) due to co-evolutionary adaptation to dermatophyte infection in European hedgehogs. The occurrence of MRSA in European hedgehogs in Finland is unknown. Consequently, we investigated the occurrence of MRSA in wild hedgehogs from urban Helsinki metropolitan area in 2020–2021 and applied whole genome sequencing (WGS) to further characterize the studied isolates and compared them with human clinical MRSA isolates. Altogether 115 dead hedgehogs were screened for MRSA using selective cultivation methods. Presumptive MRSA isolates were tested for antimicrobial susceptibility and confirmed MRSA isolates were further characterized by spa-typing and WGS. Hedgehog derived MRSA isolates were compared with clinical human MRSA isolates using core genome multilocus sequence typing (cgMLST). In total MRSA was recovered from 11 out of 115 (10%) hedgehogs. Among these four different spa types (t304; n = 4, t8835; n = 4, t5133; n = 2 and t622; n = 1) and three different sequence types (STs) (ST6; n = 6, ST7663; n = 4 and ST2840; n = 1) were identified. From the studied MRSA isolates seven harboured the mecA gene (mecA-MRSA) and four were identified as mecC-MRSA. All mecA-MRSA isolates carried immune evasion cluster genes, and one isolate was positive for Panton-Valentine leukocidin. cgMLST comparison revealed close genetic relatedness among three hedgehog and two human mecA-MRSA isolates all belonging to t304/ST6. Our results suggest a clonal dissemination of a successful MRSA clone among humans and hedgehogs. Further studies are warranted to investigate the sources and dissemination of such clone in urban environments. We observed a relatively low occurrence of mecC-MRSA in Finnish hedgehogs.