Abstract:Objective This study aims to evaluate the antibiotic resistance and transmission risk of Enterococcus faecalis (E. faecalis) in the pork production chain.Method A total of 300 samples were collected from the surface of live pigs, carcasses, and the environment in 2 pig farms, 1 slaughterhouse, and 2 markets in Hangzhou, Zhejiang. The strain identification, antibiotic resistance phenotypes, resistance genotypes, and virulence genotypes were performed by 16S rDNA sequences, broth microdilution method (MIC), and PCR. In addition, multilocus sequencing typing (MLST) and conjugational transfer tests were conducted.Result The 125 isolates of E. faecalis showed high resistance to antibiotics such as tiamulin, tetracycline, and doxycycline, and the isolates from pig farms showed higher antibiotic resistance rates than those from the slaughterhouse and markets. Ten antibiotic resistance genes were detected in the 125 strains of E. faecalis, and the detection rates of optrA, tet(M), tet(L), and erm(B) were higher. The detection rate of antibiotic resistance genes followed the trend of pig farm > slaughterhouse > market. Among the virulence genes tested, efaA was the most prevalent, followed by gelE, asa1, ace, cylA, hyl, and esp. Overall, the detection rate of virulence genes was the highest in pig farms, moderate in the slaughterhouse, and the lowest in markets. MLST results indicated that horizontal transmission was the main mechanism for the prevalence of optrA in pig-derived E. faecalis in Hangzhou, Zhejiang. The results of conjugation transfer tests showed that optrA in 12 pig-derived strains could be transferred to the recipient strain JH2-2 by plasmid conjugation.Conclusion The antibiotic resistance and transmission risk of E. faecalis in the pork production chain are assessed, which provides a theoretical basis for ensuring the safety of meat products.
