Diversity of optrA genetic structures in Enterococcus faecalis from retail chicken and the differential biofilm-forming abilities of isolates at non-frozen temperatures

Abstract Aims This study aimed to explore the diversity of optrA genetic structures in Enterococcus faecalis from retail chicken and the variance in their biofilm-forming capabilities at refrigerated and room temperatures. By comprehensively studying these two traits, we aim to fully understand the transmission and biofilm-forming capabilities at non-frozen temperatures of optrA-positive E. faecalis. Methods and results Analysis of Chinese-sourced E. faecalis genomes in the database indicated that 65.76% were optrA-positive, with animals as the predominant hosts. In 2020, 15 optrA-carrying strains were isolated from 96 retail chicken samples from four Chinese supermarkets. The optrA gene was situated on plasmids or chromosomes. A novel optrA-carrying plasmid structure was identified, resulting from IS1485-mediated structural changes. Tn6674-like and Tn558-like structures mediated inter-chromosomal transfer of optrA, while IS1216E and ISEnfa1 promoted inter-plasmid transfer. Some isolates showed a greater tendency for biofilm formation at refrigerated temperature, and others at room temperature. Conclusions In conclusion, this research reveals the genetic intricacy of optrA-positive E. faecalis and their temperature-associated biofilm-forming behaviors, highlighting the necessity of monitoring food-related microbial hazards.