Resistance and Molecular Characteristics of Methicillin-Resistant Staphylococcus aureus and Heterogeneous Vancomycin-Intermediate Staphylococcus aureus

Abstract

To investigate the molecular epidemiology of Staphylococcus aureus (S. aureus) isolated from patients in the Yellow River Delta region and to construct antibiotic resistance profiles in different genetic backgrounds. Methods: Antibiotics susceptibility testing, staphylococcal protein A (spa) typing and accessory gene regulator (agr) typing were performed for all the 204 strains. Isolates with the positive mecA gene and heterogeneous vancomycin-intermediate S. aureus (hVISA) were subjected to multilocus sequence typing (MLST) and Staphylococcal chromosomal cassettes mec (SCCmec) typing. Results: Thirty-nine MRSA strains were identified by mecA gene. Twenty-two hVISA isolates including 9 MRSA and 13 methicillinsensitive S. aureus (MSSA) strains were confirmed, the rest isolates (n = 182) were vancomycin-susceptible S. aureus (VSSA). 94.9% of MRSA and 63.6% of hVISA belonged to agrI. Fifty-seven distinct spa types including 5 novel types were mainly t309 (30.9%), t078 (11.8%) and t437 (11.8%). Fourteen sequence types (STs) containing 3 new STs were classified into 3 clone complexes (CCs) and 7 singletons among MRSA and hVISA isolates. Most MRSA isolates (87.2%) belonged to type Ⅳ SCCmec. Conclusion:The predominant genotype among MRSA population was ST59-t437-agrI-IVa (53.8%), followed by ST72-t2431-agr I-IVF (15.4%). ST72 and CC5 (ST5/965/7197) were the most common hVISA clones. Both CC59 (ST59/7437) and ST72 clones were resistant to erythromycin and clindamycin among MRSA population. Strains of MSSA with phenotypic hVISA (MS-hVISA) exhibited a striking genetic diversity accompanied by the diversification of drug resistance patterns.

ESKAPE in China: epidemiology and characteristics of antibiotic resistance

“…Moreover, there is a growing concern due to the increasing prevalence of hVISA in recent years. Shen et al identified 7.6% (36/476) hVISA among S. aureus isolated in 2010–2011 [ 73 ], while Liang et al discovered 10.8% (22/204) hVISA among isolates from inpatients and outpatients in 2019–2021 [ 74 ]. With the recent decrease in MRSA isolation rates, the proportion of MRSA among VISA/hVISA has also declined [ 73 , 74 ].…”

“…Shen et al identified 7.6% (36/476) hVISA among S. aureus isolated in 2010–2011 [ 73 ], while Liang et al discovered 10.8% (22/204) hVISA among isolates from inpatients and outpatients in 2019–2021 [ 74 ]. With the recent decrease in MRSA isolation rates, the proportion of MRSA among VISA/hVISA has also declined [ 73 , 74 ]. Liang et al reported 22.7% of hVISA isolates belonged to ST72 and CC5 (ST5/965/7197), followed by CC59 (ST59) and ST25 (18.2%, respectively), which indicated that previous dominant hVISA/VISA clone ST239 in China is changed [ 74 ].…”

“…With the recent decrease in MRSA isolation rates, the proportion of MRSA among VISA/hVISA has also declined [ 73 , 74 ]. Liang et al reported 22.7% of hVISA isolates belonged to ST72 and CC5 (ST5/965/7197), followed by CC59 (ST59) and ST25 (18.2%, respectively), which indicated that previous dominant hVISA/VISA clone ST239 in China is changed [ 74 ].…”