This french research was one of the first to draw a link between ST398 and pig farming
Pig farming is a risk factor for increased nasal Staphylococcus aureus colonization. Using sequence typing and phylogenetic comparisons, we showed that overcolonization of farmers was caused by a few bacterial strains that were not present in nonfarmers but often caused swine infections. This finding suggests a high rate of strain exchange between pigs and farmers.
Clonal comparison of Staphylococcus aureus isolate…[Emerg Infect Dis. 2005] – PubMed Result.