Identification of an SCCmec-mecC Hybrid in Methicillin-Resistant Mammaliicoccus sciuri from Australian Wildlife

Background:
Mammaliicoccus sciuri, previously known as Staphylococcus sciuri, is a commensal bacterium widely distributed in animals and an opportunistic pathogen associated with infections in animals and humans. M. sciuri may act as a reservoir of antimicrobial resistance determinants, including the staphylococcal cassette chromosome mec (SCCmec) element, which confers methicillin resistance in methicillin-resistant Staphyloccoccus aureus (MRSA) via the mecA or mecC gene. In this study, we characterized methicillin-resistant M. sciuri (MRMS) isolated from Australian wildlife.
Method:
Skin and nasal swabs were collected from 180 wild animals upon admission to a wildlife hospital in Western Australia, and from 97 animals after seven days of hospitalization. ChromID MRSA selective agar was used for the isolation of MRMS. Whole genome sequencing was performed using the Illumina NovaSeq 6000 platform and the Oxford Nanopore MinION. The PubMLST website was used to determine the sequence type (ST). SCCmec elements were annotated and analyzed using the Geneious Prime software.
Results:
Thirty-one MRMSs were isolated from 4.4% (8/180) of the animals upon admission and 23.7% of animals (23/97) after hospitalization. Three STs were identified—ST81 (n=2), ST321 (n=16) and ST337 (n=13). All MRMS isolates harboured an SCCmec element. The ST81 and ST337 MRMSs harboured an mecA-positive SCCmec III(3A); an SCCmec was reported in hospital-associated MRSA clones. In contrast, the ST321 MRMS harboured an SCCmec-mecC hybrid element which contained the mecA, mecC and blaZ resistance genes. The SCCmec-mecC hybrid consisted of the SCCmec III(3A) element fused to a partial SCCmec XI element.
Conclusion:
Methicillin-resistant M. sciuri isolated from Australian wildlife carries mecA or mecC on an SCCmec element. This study provides the first evidence of an SCCmec-mecC hybrid in M. sciuri in Australia.