[Study on drug resistance and molecular typing of food-borne Staphylococcus aureus in Ningxia, 2011-2022].

Objective: To investigate the molecular typing characteristics, drug resistance status and drug resistance gene carrying of food-borne Staphylococcus aureus in Ningxia.

Methods: Staphylococcus aureus isolated from food safety risk monitoring project in Ningxia in the past ten years were collected, drug resistance was detected using microbroth dilution method, enterotoxins were detected by real-time PCR. The strains were genotyped by pulsed field gel electrophoresis(PFGE) using SmaI endonuclease. Based on bacterial whole genome sequencing(WGS) technology, multilocus sequence typing(MLST)typing and drug resistance gene screening were performed, and the consistency between the prediction result of drug resistance genes and drug resistance phenotypes was analyzed by resfinder database.

Results: Among the 87 strains of Staphylococcus aureus, the detection rate of methicillin-resistant Staphylococcus aureus(MRSA) was 10.34%(9/87), and the detection rate of sea-see strains was 70.11%(61/87), among which two strains carried both sec and sed genes. There were 26 band types and 23 ST types from PFGE and MLST, respectively, and the dominant type was obvious. All strains were completely resistant to penicillin except teicoplanin and rifampicin, and the resistance rate to penicillin was 100.00%. The resistance rates to erythromycin and clindamycin were also relatively high, reaching 60.92%(53/87) and 45.98%(40/87). The 21 drug-resistant genes in 9 classes were analyzed, and the drug-resistant genes encoding different antibiotics were carried in different degrees. The detection rate of blaZ gene encoding penicillase was 81.61%(71/87), and the consistency rate of gene prediction result with drug-resistant phenotype was 85.05%(74/87).

Conclusion: MRSA has been isolated from food-borne Staphylococcus aureus in Ningxia, suggesting rational use of antibiotics and strengthening surveillance to slow down and control the spread of MRSA.