Enterotoxin C and Enterotoxin-Like L Associated with Post-partum Mastitis.

Denmark is a low prevalence country with regard to methicillin resistant (MRSA). In 2008 and 2014, two neonatal wards in the Copenhagen area experienced outbreaks with a typical community acquired MRSA belonging to the same type and sequence type (t015:ST45) and both were PVL and ACME negative. In outbreak 1, the isolates harbored SCC IVa and in outbreak 2 SCC V. The clinical presentation differed between the two outbreaks, as none of five MRSA positive mothers in outbreak 1 had mastitis vs. five of six MRSA positive mothers in outbreak 2 ( < 0.02). To investigate if whole-genome sequencing could identify virulence genes associated with mastitis, t015:ST45 isolates from Denmark ( = 101) were whole-genome sequenced. Sequence analysis confirmed two separate outbreaks with no sign of sustained spread into the community. Analysis of the accessory genome between isolates from the two outbreaks revealed a pathogenicity island containing enterotoxin C and enterotoxin-like L only in isolates from outbreak 2. Enterotoxin C and enterotoxin-like L carrying are associated with bovine mastitis and our findings indicate that these may also be important virulence factors for human mastitis.