Background: Staphylococcus aureus  is among the most common causes of health care- and community-associated infections worldwide. The distributions of different S. aureus  clones change over time and also vary geographically. The purpose of this study was to determine the molecular type and antimicrobial resistance profiles of clinical S. aureus  strains isolated in Urumqi, Northwestern China.
Methods: A total of 605 clinical S. aureus  isolates were collected from Xinjiang Military General Hospital, in Urumqi. Protein A-encoding (spa ) typing, multilocus sequence typing, staphylococcal chromosomal cassette mec  typing, Panton-Valentine leucocidin (pvl ) gene detection, and antimicrobial resistance profiling were performed.
Results: Among these strains, 271 isolates (44.7%) were methicillin-resistant S. aureus  (MRSA) and 334 (55.3%) were methicillin-susceptible S. aureus  (MSSA). The MRSA strains consisted of 22 spa  types and 14 sequence types (STs). ST239-MRSA-III-t030 (73.1%, 198/271) and ST59-MRSA-IV-t437 (11.8%, 32/271) were the most common, and ST22-MRSA-IV-t309 was the rarest (2.02%, 6/271). The MSSA strains consisted of 93 spa types and 29 STs. ST22, ST121, ST398, ST5, ST7, ST188, and ST15 were the main MSSA STs, and ST22-MSSA-t309 was most common (26.0%, 87/334). The pvl  gene was present in 20.3% of all S.aureus  strains, and 80.8% (88/99) of ST22-MSSA strains harbored the pvl  gene. A total of 85.7% pvl -positive ST22-MSSA strains were spa  t309 (85/99), and 87.5% of pvl -positive ST22-MSSA strains were from abscesses or wounds (skin and soft tissue infections). All ST239-MRSA strains were resistant to gentamicin (GEN), levofloxacin (LEV), ciprofloxacin (CIP), moxifloxacin (MXF), rifampicin (RIF), and tetracycline (TET). Among the ST59-MRSA strains, over 70.0% were resistant to erythromycin (ERY), clindamycin (CLI), and TET. ST22-MSSA remained susceptible to most antibiotics, but was resistant to PEN (97.0%), ERY (57.6%), and CLI (15.2%).
Conclusion: Our major results indicated that the antimicrobial resistance profiles and pvl  genes of S. aureus  isolates from Urumqi were closely associated with clonal lineage. ST239-MRSA-III-t030 and pvl -positive ST22-MSSA-t309 were the most common clones in this region of Northwestern China.
Keywords: Staphylococcus  aureus, methicillin-sensitive Staphylococcus aureus , methicillin-resistant Staphylococcus aureus , pvl  gene, molecular typing