Structures of SCC elements in methicillin-resistant are closely related to those harboured by community-associated methicillin-resistant .

Methicillin-resistant (MRSL) is increasingly recognized in healthcare and community settings. To obtain a better understanding of the emergence of MRSL, this study characterized the structure and content of the SCC elements harboured by 36 MRSL isolates obtained from diverse sources in Hong Kong from 2008 to 2017. The isolates were investigated by whole-genome sequencing. SCC types and subtypes were assigned according to the guidelines from the International Working Group on the Classification of Staphylococcal Cassette Chromosome Elements. The sequence type (ST)-SCC combinations in the 36 MRSL isolates were as follows: ST3-SCC IV (=2), ST3-SCC V (=28), ST27-SCC V (=5) and ST42-SCC V (=1). The two SCC IV elements were highly similar to the SCC IV element harboured by the community-associated methicillin-resistant (CA-MRSA) strain, JCSC6668. The J3 complex-J2 regions in the SCC V elements were highly similar to the corresponding regions in the CA-MRSA strains PM1 (=13) or WIS (=21). Based on the J1 to J3 sequences, the SCC V elements can be categorized into nine different subtypes. Our findings highlight the diversified structures of SCC elements among MRSL strains and their close relationship with SCC elements harboured by CA-MRSA.