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The isolation of meticillin-resistant Staphylococcus aureus (MRSA) from farmers led to the recognition of a zoonotic MRSA lineage (ST398) in pigs in Europe and elsewhere (Khanna and others 2008, European Food Safety Authority (EFSA) 2009). Recent studies revealed that ST9 is the predominant livestock-associated MRSA (LA-MRSA) strain in China (Cui and others 2009, Guardabassi and others 2009).
In Hong Kong (HK), pig farming has declined markedly, and the 40 remaining farms, each with around 600 animals kept in covered outdoor pens, produce around 400 pigs per day. Approximately 93 per cent of the 4600 pigs slaughtered daily in HK are transported by train from several areas of mainland China to a central abattoir. ST9 has been reported from farms in northern China (Cui and others 2009), but no data are available about the type and frequency of LA-MRSA in pig farms in southern China, where there are numerous very large establishments.
This study investigated carriage rates and characterised LA-MRSA by convenience sampling at two large-scale intensive farms in Guangdong (farm 1, 105 samples; farm 2, 150 samples) and two small-scale farms in HK (farm 1, 100 samples; farm 2, 120 samples). Risk of cross-contamination during transport and slaughter was assessed in LA-MRSA-negative pigs.
Nasal swabs (Transwabs; Medical Wire and Equipment) were collected from approximately equal numbers of weaners, finishers and breeding sows at all farms (Table 1). At the HK farms only, five environmental swabs from farm rails, slurry, pigs' drinking water containers and workers' boots …