The aim of this study is to investigate the genetic backgrounds of methicillin susceptible Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA) and heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) isolates isolated from clinical specimens of the patients with verified infections in a Chinese teaching hospital. Macro E test (MET) was used to detect hVISA and multilocus sequence typing (MLST) was used to determine the STs of the selected isolates.

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... genotypes of SCCmec were determined by multiplex polymerase chain reaction (PCR) in MRSA isolates. Panton-valentine leucocidin (PVL) genes were also detected by PCR. Among 273 S. aureus isolates, hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA), community-associated methicillin-resistant S. aureus (CA-MRSA), hospital-acquired methicillin susceptible Staphylococcus aureus (HA-MSSA) and community-associated methicillin susceptible Staphylococcus aureus (CA-MSSA) isolates accounted for 55.6, 1.5, 36.3, and 6 .6%, respectively. Nine isolates were confirmed as hVISA by MET. Among 60 HA-MRSA isolates, ST239-MRSA-III was the most prevalent clone accounting for 51.7%, followed by ST5-MRSA-II clone. Fifty percentage and 22.2% of CA-MSSA isolates were found to be ST121 and ST88. ST239-MRSA-III was the predominant clone in hVISA isolates. However, no predominant ST type was found in HA-MSSA isolates. Of 9 PVL-positive strains, ST88 was the most prevalent ST (50.0%; 4/8), followed by ST121 (33.3%; 3/9), ST5 (4.5%; 1/22) and ST239 (2.6%; 1/39). In conclusion, ST239-III was the major pandemic clone in hVISA and HA-MRSA and spread in China. ST5-emerging rapidly in China had remained stable viability.