Molecular epidemiology and geographical variation of methicillin-resistant Staphylococcus aureus: a multicentre study...

This multicentre study investigated the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates across Xinjiang, China. We aimed to characterise resistance phenotypes, genotype distributions, virulence gene profiles, and regional variations to inform precise prevention strategies and clinical treatment of MRSA infections in Xinjiang.

MRSA clinical isolates (122) were collected from hospitals in Urumqi, Alaer, Tumxuk, and Yining cities. Following identification by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and mecA gene PCR confirmation, isolates underwent molecular characterisation using multilocus sequence typing (MLST), staphylococcal cassette chromosome mec (SCCmec) typing, and staphylococcal protein A (spa) typing. Antimicrobial susceptibility testing was conducted to evaluate resistance phenotypes according to the 2023 guidelines of the Clinical and Laboratory Standards Institute (CLSI). PCR was used to detect 16 resistance genes and 13 virulence genes.

Among 122 MRSA isolates, significant regional variations were observed in the prevalence of resistance (ermC, tetK, tetM, aac(6')-aph(2''), and aph(3')-III) and virulence (seb, sdrC, cap5H, and cap8H) genes (P < 0.05). Molecular typing revealed that CC59-ST59 (52.46%) and CC22-ST22 (18.03%) were the predominant clonal groups in Xinjiang. ST59 was dominant in Urumqi (63.27%) and Alaer (61.29%), whereas ST22 prevailed in Yining (37.50%) and Tumxuk (34.62%). All isolates were resistant to penicillin and oxacillin. Fluoroquinolone resistance (22.45%-34.62%) was higher in Urumqi and Tumxuk, whereas tetracycline resistance (45.16%) was elevated in Alaer. Notably, ST22 clones from Xinjiang displayed unique spa types (t223 and t005), which were distinct from those in other Chinese regions. A Tumxuk-specific ST22-t005-IV clone exhibited multidrug resistance (ten antibiotic classes) and high virulence (100% carrying pvl, tsst-1, and four other virulence genes).

MRSA epidemic strains in Xinjiang exhibit significant regional heterogeneity in molecular typing, resistance, and virulence profiles. Attention should be paid to the drug resistance of MRSA in different regions, while enhanced clinical surveillance is warranted for the unique spa type evolution within the ST22 lineage, particularly the highly virulent and multidrug-resistant ST22-t005-IV clone.