Abstract
The aim of this study is to investigate the genetic backgrounds of methicillin susceptibleStaphylococcus 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. The 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-â…¡emerging rapidly in China had remained stable viability. Key words: Staphylococcus aureus, heterogeneous vancomycin-intermediate Staphylococcus aureus, molecular characteristic.
Highlights
Staphylococcus aureus is one of the most virulent and common pathogens, accounting for a wide range of different serious infections from minor skin and soft tissue infections (SSTIs) to life threatening pneumonias and sepsis (Valentini et al, 2008)
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 isolates isolated from clinical specimens of the patients with verified infections in a Chinese teaching hospital
Twenty-two isolates (8.1%, 22/273) were classified as community- acquired, of which 18 isolates belonged to community-associated methicillin susceptible Staphylococcus aureus (CA-MSSA) and 4 isolates belonged to community-associated methicillin-resistant S. aureus (CA-MRSA)
Summary
Staphylococcus aureus is one of the most virulent and common pathogens, accounting for a wide range of different serious infections from minor skin and soft tissue infections (SSTIs) to life threatening pneumonias and sepsis (Valentini et al, 2008). Since methicillin-resistant S. aureus (MRSA) first appeared in 1961 (Kowalski et al, 2005), MRSA has become a major cause of hospital- and community-acquired infections worldwide. MRSA is conferred by an acquired penicillin-binding protein encoded by the mecA gene located on a mobile genetic element, the Staphylococcal cassette chromosome mec (SCCmec). Seven different SCCmec types with difference in size and construe (types I, II, III, IV, V, VII and VIII) have been found (Ito et al, 2004). SCCmec is regarded as an antibiotic-resistant island, as it can be integrated by other mobile elements and resistance genes. MRSA isolates are mostly multi-resistant to many antimicrobial agents, such as macrolides, aminoglycosides and fluoroquinolones. Measures should be taken to control the spread of MRSA in both hospitals and communities
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