Background Methicillin-resistant Staphylococcus aureus (MRSA) is a major global problem. The analysis of the molecular characteristics and changing trend of MRSA is essential for the control and treatment of diseases caused by the pathogen.
Methods A total of 162 MRSA isolates from invasive infections between 2012 and 2018 were collected, molecular typing and antimicrobial susceptibility tests to explore its molecular epidemiologic change in a hospital were performed.
Results All of the 162 MRSA isolates (86.4% HA-MRSA and 13.6% CA-MRSA) were divided into 16 different ST and 30 Spa types. The major STs were ST5 (96/162, 59.3%) and the predominant spa type was t311(83/162, 51.2%). Five SCCmec types were found and the most common SCCmec type was type II (101/162, 61.7%). The prevalence of ST5 MRSA gradually declined from 2014 to 2018 but the prevalence of ST59 MRSA significantly increased. At the same time, livestock-associated methicillin-resistant S.aureus ST239 and ST9 were detected. 28 isolates were Panton-valentine leucocidin (pvl) gene positive (28/162, 17.3%). The most prevalent pvl-positive clone was ST59-IVa-t437. Comparing with HA-MRSA, CA-MRSA had a lower probability of ST5 (9.1% vs, 67.1%, P=0.000) but a higher probability of ST59 (63.6% vs. 11.4%, P=0.000), not only that, it was more likely to carrying pvl-positive gene (36.4% vs. 14.3%, P=0.028).
Conclusions The molecular types of MRSA were getting complex over time. ST5-II-t311 was the predominant clone of MRSA isolate with a downward incidence from 2012 to 2018. ST59 MRSA strains, which is thought community related strain are spreading into hospitals and has an upward incidence during the investigational period.