Molecular epidemiology and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus isolates in...

Methicillin-resistant Staphylococcus aureus (MRSA) is a public health problem worldwide. This study aimed to investigate the antimicrobial susceptibility and molecular epidemiological characteristics of MRSA strains in Xiangyang, China, during 2012-2014.

Eighty non-duplicate S. aureus isolates from clinical specimens were collected from four tertiary hospitals. MRSA strains were identified and were tested for antibacterial susceptibility. Staphylococcal cassette chromosome mec (SCCmec) typing, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and staphylococcal protein A (spa) typing were performed to explore molecular characteristics.

Among the 80 S. aureus isolates, 43 MRSA (53.8%) were detected. MRSA strains exhibited resistance against non-β-lactam antibiotics to varying degrees. SCCmec type III was the predominant type (39/43; 90.7%), and the remainder were SCCmec type IVa (4/43; 9.3%). Thirteen MLST types were found, mainly ST239 (12/43; 27.9%) and ST59 (7/43; 16.3%). Fifteen spa types were found, mainly t437 (13/43; 30.2%) and t030 (6/43; 14.0%). PFGE grouped the 43 MRSA isolates into five types. SCCmecIII-ST239-t030/t632 and SCCmecIII-ST59/ST338-t437 were the dominant epidemic clones in this region. ST239-t030/t632/t037 was the epidemic clone with the most serious drug resistance.

This region presented a high MRSA rate and the MRSA isolates demonstrated strong antimicrobial resistance. The existence of four strains of community-acquired MRSA (SCCmec type IVa) indicated the dissemination of MRSA strains from the community to hospitals. The epidemic situation and drug resistance of MRSA should be regularly monitored. Effective measures should be adopted to prevent and control the occurrence of infection in hospitals.