Where has the ST 398 MRSA come from and how does it spread to man?
Although originally it was thought that the ST398 emerged as a resistance phenotype (strain) independent of human MRSA, the current thinking is that a swine-adapted MSSA (Methicillin susceptible S. aureus) acquired a gene (mecA) from a human CA-MRSA by direct gene transfer to the swine MSSA. Thus, the swine MSSA became a swine MRSA. However, further studies are needed to confirm this hypothesis. The most likely way that ST398 MRSA transfers from animals to man is via the environment in the pig house. The organism can survive for some time in dust and pig houses inevitably are sources of dust. In 2010 in the UK, we can expect a report on a major survey containing the results of tests from over 300 pig herds. This should give a valuable insight into possible incidence and reasons for its occurrence, as well as helping design new prevention programmes and possible additional biosecurity measures. References Elston J W T, Barlow G D Community–associated MRSA in the UK, J Infect (2009) doi:
