Comparison of the Staphylococcal Chromosome Cassette (SCC) mec in Methicillin-Resistant Staphylococcus aureus (MRSA) and Non-aureus Staphylococci (MRNAS) from Animals and Humans

Methicillin-resistant Staphylococcus aureus (MRSA) and non-aureus staphylococci (MRNAS)
cause different infections in animals, including mastitis, in livestock and humans. This study aimed
to identify and compare the staphylococcal chromosome cassette mec (SCCmec) types of MRSA or
MRNAS isolated from several animal species and humans in different countries. Of 1462 S. aureus
and non-aureus staphylococci, 68 grew on Chrom MRSA ID® agar, were phenotypically resistant to
cefoxitin and tested positive with the PCR for the mecA gene. These 60 MRSA and 8 MRNAS were
isolated in Belgium mainly from cows (livestock-associated (LA) MRS) and humans (communityacquired (CA) MRS) and in Japan from dogs and cats. The SCCmec cassettes were identified by
multiplex PCR in 52 MRSA and 7 MRNAS and by whole genome sequencing (WGS) in 8 additional
MRSA. The SCCmec types IV and V were the most frequent in Belgian LA-MRS and CA-MRS, while
the SCCmec type II was identified in four of the five Japanese MRSA. The remaining isolate was a
bovine S. haemolyticus in which no SCCmec was identified. These results confirm the high prevalence
of the SCCmec types IV and V in LA-MRS and CA-MRS in Belgium, emphasizing the possible public
health hazard of the former, and the absence of SCCmec in some MRNAS.