Isolation, Identification and Biofilm Formation Ability of Escherichia coli from Pork

This paper aims to investigate the biofilm formation and related genes expression of Escherichia coli isolated from pork. E. coli was isolated from pig slaughtering line, carcass surfaces and pork meat and identified using selective agar plates and specific polymerase chain reaction (PCR). After culture at 15 ℃ for 72 h, the biofilm forming abilities of the isolates were evaluated by means of microplate crystal violet staining. Furthermore, representative strains were selected to explore the changes of biofilm biomass, the composition of extracellular polymeric substances (EPS), and biofilm related-genes expression by means of reverse transcription real-time PCR in the process of biofilm formation. The results showed that a total of 31 strains of E. coli were isolated and identified in this study, among which 11 were obtained from pig slaughtering line, 4 from the surface of pig carcasses, and 16 from raw pork meat. The results of crystal violet staining showed that there were significant differences in the biofilm-forming ability among the 31 isolates, and 64.52% of them had weak biofilm-forming ability, one of which was then selected to study the biofilm formation process. The biofilm biomass of strain D_4-18 on the microplate increased continuously during 168 h incubation at 15 ℃. After incubation for 72 and 168 h, EPS were secreted by strain D_4-18, and the gene expression levels of papC、fimH、csgA genes were 0.095、0.933、0.435 copies/cm², respectively. With the increase of culture time, the contents of protein and polysaccharide in loose EPS (L-EPS) and the protein content in bound EPS (B-EPS) increased significantly (P < 0.01). After incubation for 168 h, the expression of the papC and fimH genes increased, while csgA gene expression did not change significantly, indicating that these genes play different regulatory roles in the biofilm formation of E. coli.