Indications for both host-specific and introduced genotypes of Staphylococcus aureus in marine mammals

Staphylococcus aureus is present in the marine environment and causes disease in marine mammals. To determine whether marine mammals are colonized by host-specific strains or by strains originating from other species, we performed multi-locus sequence typing on ten S. aureus strains isolated from marine mammals in the U.K., the Netherlands, and the Antarctic. Four new sequence types of S. aureus were discovered. S. aureus strains from a southern elephant seal (n = 1) and harbour porpoises (n = 2) did not cluster with known S. aureus strains, suggesting that they may be host species-specific. In contrast, S. aureus strains from harbour seals (n = 3), other harbour porpoises (n = 3), and a grey seal (n = 1) clustered with S. aureus strains previously isolated from domestic ruminants, humans, or birds, suggesting that these S. aureus strains in marine mammals were introduced from terrestrial species.