Population structure of Staphylococcus aureus in China

The present PhD research was aimed at analysing the population structure of Staphylococcus aureus in China. Between 2000 and 2005 we found that patients from a single Chinese hospital showed increasing trends in antimicrobial resistance. Among methicillin-resistant S. aureus (MRSA), resistance against rifampicin doubled to 68%. Staphylococcal food poisoning (SFP) is frequent in China. Two predominant S. aureus lineages, ST6 and ST943, were identified causing outbreaks of SFP in Southern China between 2006 and 2009. An investigation on 590 slaughter pigs in Northern China showed that the major type of methicillin-sensitive S. aureus (MSSA) was ST398 (61.1%) and all MRSA belonged to ST9. Moreover, a novel resistance determinant, lsa(E), was identified among quinupristin/dalfopristin-resistant strains with the ST9 type. A community survey showed that 16.5% of healthy Chinese individuals carried S. aureus with a low prevalence of MRSA (0.36%). Three risk factors were associated with S. aureus nasal carriage, namely city of residence, age and non-Han ethnicity. The CC398 and CC5 lineages were the most prevalent in this surveyed population. A comparison between contemporary strain collections from China and Europe revealed significant differences in the composition of the genetic population structures between both geographical regions. Lastly, the SasX protein was shown to have no influence on the motility of the most frequent healthcare-associated MRSA in China (ST239) suggesting that motility changes cannot explain the success of this lineage. Altogether, these studies uncovered systematic differences in the S. aureus populations in China and Europe, two opposite ends of the same continental shelf