Epidemiological and genetic diversity of Staphylococcus aureus causing bloodstream infection in Shanghai, 2009-2011.

OBJECTIVES: Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) has been an important pathogen causing bloodstream infections. Our study aimed to investigate the epidemiological and genetic diversity of clinical S. aureus isolates from patients with bloodstream infection in four hospitals of Shanghai from 2009 to 2011. METHODS: A collection of S. aureus isolates causing bloodstream infection from four hospitals in the central part of Shanghai was carried out. Antimicrobial susceptibility testings of collected isolates were performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, and spa-type, multi-locus sequence typing, agr type and toxin gene profiling were performed to explore the molecular diversity. Moreover, MRSA strains were also characterized by Staphylococcal cassette chromosome mec (SCCmec) typing. RESULTS: The drugs such as linezolid, teicoplanin and vancomycin were efficacious for treating S. aureus including MRSA bloodstream infection. Methicillin-sensitive Staphylococcus aureus (MSSA) strains displayed distinct diversity in molecular characterization and toxin genes, and three virulent MSSA strains encoding at least five toxins were detected. Five community-associated MRSA (CA-MRSA) strains were found, but the majority (88.7%) of MRSA strains belonged to two epidemic clones (ST239-MRSA- III and ST5-MRSA- II) with different toxin gene profiles among patients with bloodstream infection. CONCLUSIONS: Healthcare-associated MRSA (HA-MRSA) strains were still the main pathogen causing bloodstream infections in spite of the emergence of CA-MRSA strains in hospital setting.

Molecular epidemiologic analysis of Staphylococcus aureus isolated from four burn centers.

Staphylococcus aureus has been a major cause of hospital-acquired infections. Methicillin-resistant Staphylococcus aureus (MRSA) has emerged since 1980s as an epidemiologic problem in hospitals. This old pathogen brings a new challenge to all physicians and bacteriologists. Hence, effective measures of MRSA control are in critical need. S. aureus or MRSA is one of the leading causes of infection among burn centers, resulting in a number of poor outcomes and even death. The present study performed a molecular epidemiologic analysis of S. aureus isolated from four burn centers in the southeast of China. A total of 85 isolates were collected, and molecular characters were determined for further investigation. In this study, the prevalent clone of MRSA among four burn centers was found to be SCCmec III (spa-type t030, agr I), which is resistant to 4 kinds of antimicrobials including erythromycin, clindamycin, kanamycin and mupirocin. Discrepancy between mecA detection and conventional tests used for MRSA identification was observed unintentionally. Our data demonstrated that the overall prevalence rate of MRSA was 55.3%, and drugs such as sulfamethoxazole/trimethoprim, linezolid and fusidic acid are efficient antibiotic options for treating S. aureus or MRSA infections among four burn centers studied in present investigation.