Molecular characterization of Staphylococcus epidermidis strains isolated from a teaching hospital in Shanghai, China

Staphylococcus epidermidis is a leading cause of hospital-acquired infections, mostly associated with the use of medical devices in seriously ill or immunocompromised patients. Currently, the clonal characteristics of S. epidermidis in the hospital environment in China are unknown; neither is it known why these sequence types are easily disseminated in the hospital setting. In this study, multilocus sequence typing (MLST) was employed for the clonal analysis of 80 S. epidermidis isolates collected from patients with S. epidermidis infections. MLST revealed a total of 16 different sequence types among these isolates. ST2, which contained exclusively ica-positive, IS256-positive and biofilm-forming isolates, represented the majority of clinical strains tested. Of the S. epidermidis strains circulating in the hospital environment in China, as many as 96.25% are resistant to meticillin. Four staphylococcal chromosomal cassette mec (SCCmec) types were identified among the total 80 S. epidermidis isolates, none of the strains carried an SCCmec I cassette. All of the ST2 isolates carried the SCCmec type Ill cassette. Taken together, the combination of biofilm-forming ability and antibiotic resistance helps ST2 become successfully established within nosocomial environments, and promotes the device-related infection and bacteraemia.