S almonella infection in grey seals ( H alichoerus grypus ), a marine mammal sentinel species: pathogenicity and molecular typing of S almonella strains compared with human and livestock isolates

Microbial pollution of the marine environment through land–sea transfer of human and livestock pathogens is of concern. S almonella was isolated from rectal swabs of free‐ranging and stranded grey seal pups (21.1%; 37/175) and compared with strains from the same serovars isolated from human clinical cases, livestock, wild mammals and birds in Scotland, UK to characterize possible transmission routes using pulsed‐field gel electrophoresis and multi‐locus variable number of tandem repeat analyses. A higher prevalence of S almonella was found in pups exposed to seawater, suggesting that this may represent a source of this pathogen. S almonella Bovismorbificans was the most common isolate (18.3% pups; 32/175) and was indistinguishable from isolates found in Scottish cattle. S almonella T yphimurium was infrequent (2.3% pups; 4/175), mostly similar to isolates found in garden birds and, in one case, identical to a highly multidrug resistant strain isolated from a human child. S almonella H aifa was rare (1.1% pups; 2/175), but isolates were indistinguishable from that of a human clinical isolate. These results suggest that S . Bovismorbificans may circulate between grey seal and cattle populations and that both S . Typhimurium and S . Haifa isolates are shared with humans, raising concerns of microbial marine pollution.