Epidemiological Characteristics of MRSA Strains Isolated from Fresh Pork Sources of Chengdu City

Objective:The epidemiological characteristics of methicillin-resistant Staphylococcus aureus(MRSA)isolated from fresh pork samples were investigated.Methods:MRSA isolates from fresh pork samples were conducted for MLST,spa and SCCmec typing. The enterotoxin genes,disinfectant resistance gene,biofilm genes and drug resistance genes carried by MRSA isolates were detected by polymerase chain reaction(PCR)method. The antibiotics sensitivity of MRSA was also investigated by K-B disc diffusion method. Results:In this study,24 strains of MRSA were screened from 297 S. aureus isolates of fresh pork origin,with an isolation rate of 8.08%.The main types of MRSA isolates were ST88-IVa-t1376,ST59-IVa-t437 and ST9-IVb-t3433. Most isolates carried 3~7 antibiotics resistant tested genes. All the MRSA strains were resistant to ampicillin and penicillin G,and multi-drug resistances existed. At the same time,MRSA strains carried multiple enterotoxin genes,of which,MRSA8 and MRSA13 carried the complete egc gene cluster. These isolates contained biofilm-forming related genes clfB,eno,icaBC and sasG. The anti-disinfectant genes qacA/B,qacC and qacG were carried by 62.5% of the isolates,and qacG gene was the main type. In addition,79.17% of MRSA carried hemolysin genes(hla,hlb). The pvl gene was not detected in all MRSA strains.Conclusion:The prevalence of pork-sourced MRSA in Chengdu might have cross-contamination and the monitoring of MRSA strains carried by animal-derived foods should be strengthened.