Surveillance of Antibiotic Resistance and Molecular Epidemiology of

To investigate the distribution, drug resistance patterns, multi-locus sequence typing (MLST), and virulence gene carriage of Staphylococcus aureus in the Baotou region of Inner Mongolia, China. From January 2018 to December 2020, clinical isolates of S. aureus were collected from 11 hospitals in Baotou participating in the China Antimicrobial Resistance Surveillance System (CARSS). Data were analyzed using WHONET 5.6 and SPSS 26.0. Ninety methicillin-resistant S. aureus (MRSA) strains from 2020 were typed by MLST, with results analyzed via the eBURST program. Ninety randomly selected methicillin-sensitive S. aureus (MSSA) strains from 2020, along with the 90 MRSA strains, underwent polymerase chain reaction to detect 20 virulence genes, including clfa, clfb, fnbB, scn, chp, sak, coa, nuc, ebps, eno, cna, and bbp. A total of 2453 S. aureus strains, including 309 MRSA, were isolated. Secretions were the main source for S. aureus (38.0%), and sputum for MRSA (16.7%). MRSA showed higher resistance to most antimicrobials than MSSA. Among eight identified sequence types, ST59 dominated (60%), mainly linked to hospital-acquired surgical infections (66.7%, 36/54). All strains carried hla, hld, nuc, clfa, and clfb genes, and over 90% carried sak, scn, and coa genes. The fnbB gene detection rate was significantly higher in MSSA (83%) than in MRSA (15%). Detection rates of chp, pvl, and LukED genes varied significantly among sequence types. The detection rate of the pvl gene was 67% in ST22 strains, which was higher than that observed in the ST59, ST398, and ST25 strains. The isolation rates of S. aureus and MRSA in Baotou are lower than the national averages, with no strains resistant to vancomycin, linezolid, or teicoplanin. The predominant MRSA strain in this region is ST59. The S. aureus strains in this region carry a large number of virulence genes, indicating high virulence.