Molecular characterization and virulence gene profiling of methicillin-resistant Staphylococcus aureus associated with bloodstream infections in southern China

Rui Zhao; Xing Wang; Xinhui Wang; Bingyu Du; Kexin Xu; Faming Zhang; Changhong Jiang; Yanfeng Zhao; Yefei Zhu

doi:10.3389/fmicb.2022.1008052

Molecular characterization and virulence gene profiling of methicillin-resistant Staphylococcus aureus associated with bloodstream infections in southern China

Front Microbiol. 2022 Oct 17:13:1008052. doi: 10.3389/fmicb.2022.1008052. eCollection 2022.

Authors

Rui Zhao¹, Xing Wang², Xinhui Wang¹, Bingyu Du¹, Kexin Xu¹, Faming Zhang³, Changhong Jiang⁴, Yanfeng Zhao¹, Yefei Zhu¹

Affiliations

¹ Laboratory Medicine Center, The Second Affiliated Hospital, Nanjing Medical University, Nanjing, China.
² Department of Laboratory Medicine, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
³ Medical Center for Digestive Diseases, The Second Affiliated Hospital, Nanjing Medical University, Nanjing, China.
⁴ Department of Laboratory Medicine, Zhujiang Hospital, Southern Medical University, Guangzhou, China.

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) causes an enormous illness burden, including skin and soft tissue infections (SSTIs), pneumonia, bloodstream infections (BSI), and sepsis. BSI are associated with significant patient morbidity and mortality worldwide. However, limited information is available on MRSA-related BSI in China. This study aimed to investigate the molecular characterization of 77 MRSA isolates recovered from hospitalized patients with BSI between 2012 and 2020 at three first-class tertiary hospitals in southern China based on multilocus sequence typing (MLST), spa typing, and staphylococcal cassette chromosome mec (SCCmec) typing. Overall, 13 clonal complexes (CCs) were identified, with CC59 and CC5 being the largest clusters, indicating high genetic diversity among BSI-causing MRSA isolates. ST59 was the most prevalent MLST type (22.1%). ST5/ST764-MRSA SCCmec II was the predominant adult MRSA clone, whereas ST59-MRSA SCCmec IV was the most common pediatric MRSA clone. ST5-t2460, ST764-t1084, and ST59-t437 were the most common types of adult MRSA isolates, whereas ST59-t437 and ST59-t172 were the predominant types of children's MRSA isolates. ST59-SCCmec IV/V represented the most common clone among community acquired-MRSA isolates. ST5/ST764-SCCmec II was the most common type of hospital-associated MRSA isolate. The most prevalent toxin-encoding genes detected were hla, hld, icaA, and clfA (96.1-100%). Forty-three (100%, 43/43) isolates harbored more than 18 of the tested virulence genes in adults and eight virulence genes (23.5%, 8/34) in children. Virulence gene analysis revealed diversity among different clones: the positivity rates for the Panton-Valentine leukocidin (PVL) gene were 55.8 and 35.3% in adult and pediatric MRSA isolates, respectively; the genes seb-sei were present in all adult strains; seb-seg-sei-seo were present in all ST5, ST59, ST15, ST45, and ST22 adult strains; and seg-sei-sem-sen-seo were present in different clones, including ST15, ST45, and ST22 adult MRSA isolates and ST25, ST30, ST546, and ST72 children's MRSA isolates. Adult MRSA isolates had significantly higher antibiotic resistance rates and virulence gene prevalence than pediatric MRSA isolates. For 8 years, this study provided epidemiological data on the molecular characteristics and virulence genes in different groups of MRSA BSI in China. Our findings may provide critical information for a better understanding of MRSA BSI.

Keywords: antibiotic resistance; bloodstream infection; methicillin-resistant Staphylococcus aureus; sequence typing; virulence genes.