Comparison of community- and healthcare-associated methicillin-resistant Staphylococcus aureus isolates at a Chinese tertiary hospital, 2012-2017

The transmission between community-associated (CA-) and healthcare-associated (HA-) methicillin-resistant Staphylococcus aureus (MRSA) has increased the challenge of infection control. To understand the clonal evolution and transmission of MRSA isolates, we compared the characteristics of 175 CA-MRSA and 660 HA-MRSA strains at a Chinese tertiary hospital in 2012-2017. Antibiotic susceptibility was performed on VITEK system, the genetic background of the isolates was characterized by SCCmec, spa, and MLST typing, while virulence determinants were screened using conventional PCR. Although more than 70% of the CA-MRSA isolates were erythromycin and clindamycin resistant, CA-MRSA was more susceptible than HA-MRSA to most of the antibiotics tested. ST239-MRSA-III-t030 (30%) was the most prevalent clone among HA-MRSA, while ST59-MRSA-IVa-t437 (28.8%) was the major clone among CA-MRSA. Notably, ST59-MRSA-IVa-t437 accounted for 6.7% of the chosen HA-MRSA isolates. Additionally, difference in virulence gene content was found between the CA-and HA-MRSA strains. In conclusion, epidemiological characteristics were largely different between CA-and HA-MRSA. Although ST239-MRSA-III-t030 is still the predominant clone among HA-MRSA, the community clone ST59-MRSA- IVa-t437 has the potential of becoming an essential part of HA-MRSA in the region tested.