Phenotypic and molecular characteristics of methicillin-resistant Staphylococcus aureus isolated from food and clinical samples
Objective To investigate the drug resistance,biofilm formation ability,and molecular characteristics of methicillin-resistant Staphylococcus aureus(MRSA)isolated from food and clinical samples.Methods A total of 21 MRSA strains isolated from commercial food and 30 MRSA strains isolated from clinical cases in a Class 3 Grade A hospital in Shaanxi from 2019 to 2020 were tested for drug susceptibility,MLST,spa,SCCmec typing,and biofilm formation ability.The phylogenetic analysis of strains from different sources was performed based on SNP by whole genome sequencing.Results The resistance rates of 51 MRSA strains to penicillin,oxacillin,erythromycin,clindamycin,tetracycline,and other antibiotics exceeded 50%.Penicillin and oxacillin exhibited the highest resistance rates(100%),followed by erythromycin,clindamycin,and tetracycline with resistance rates of 98.04%,96.08%,and 52.94%respectively.The ST59-t437-IVa(2B)molecular type was predominant among 21 food MRSA strains and 30 clinical MRSA strains,accounting for 52.38%(11/21)and 36.67%(11/30),respectively.Among the 21 food-borne MRSA strains,38.09%(8/21)exhibited the capacity for biofilm formation,while all 30 clinical MRSA strains demonstrated biofilm-forming ability.The phylogenetic analysis revealed that ST59-t437-IVa(2B)constituted the primary evolutionary lineage of MRSA strains isolated from both food and clinical samples,with some strains from these two sources falling within the same evolutionary branch.Conclusion The drug-resistant types and rates of drug resistance in MRSA strains isolated from both food and clinical sources exhibited a high degree of consistency in this study.Moreover,the biofilm formation ability was found to be stronger in clinical MRSA isolates compared to those derived from food-borne sources.Additionally,close genetic relationships were observed between certain MRSA strains obtained from both food and clinical samples,highlighting the significance of further research and attention towards the risk posed by food-borne MRSA.
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