Livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA) CC398 isolated from UK animals belong to European lineages

n recent years there has been an increase in the number of livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA) clonal complex (CC) 398 recovered from animals in the UK. To determine possible origins of 12 isolates collected throughout the UK between 2013- 2015, whole genome sequences (WGS) of eighty-nine CC398 European and non-European isolates from diverse animal hosts, were compared. Phylogenetic reconstruction applied to WGS data to assess genetic relatedness, clustered all 12 UK CC398 LA-MRSA within the European sub-lineages, although on different nodes; implicating multiple independent incursions into the UK. Three UK isolates from healthy pigs and one from turkey clustered within the ccrC spa-type t011 European sub-lineage and three UK isolates from horses within the ccrA2B2 t011 European sub-lineage. The remaining UK isolates, mostly from pigs, clustered within the t034 European lineage. Presence of virulence, antimicrobial (AMR), heavy metal (HMR), and disinfectant (DR) resistance genes were determined using an in-house pipeline. Most isolates, including from the UK, harboured resistance genes to =3 antimicrobial classes in addition to ß-lactams. HMR genes were detected in most European ccrC positive isolates, with >80% harbouring czrC, encoding zinc and cadmium resistance; in contrast only 60% ccrC isolates within non-European lineages and 6% ccrA2B2 isolates showed this characteristic. The UK turkey MRSA isolate did not harbour fAVß avian prophage genes, SAV_2008 and SAV_2009 present in US MSSA isolates from turkey and pigs. Absence of some of the major human-associated MRSA toxigenic and virulence genes in the UK LA-MRSA animal isolates was not unexpected