Biofilm Formation Of Escherichia Coli Isolated From Retail Chicken And Tannin-rich Fraction From Pomegranate Rind Inhibits Biofilm Formation In Escherichia Coli

Escherichia coli(E. coli) is a common Gram negative opportunistic pathogen, some certain pathovars can cause sevrere acute or chronic infection affect either animals or humans worldwide. Generally, it is considered an indicator of fecal contamination in food and water. Bacterial biofilms are multicellular communities of bacteria that attach to abiotic or biotic surfaces and produce an extracellular polymeric matrix. Bacteria within a biofilm are protected against several stresses including antibiotics and disinfectants compared with their planktonic counterparts.Pomegranate(Punica granatum L.) is an ancient fruit from Middle East, and its biological properties such as anticancer, prevention of cardiovascular diseases and diabetes and antibacterial has been well promoted. Anthocyanins, ellagitannins and hydrolyzable tannins are the main phytochemicals of pomegranate. In this study, biofilm formation of E. coli isolated from retail chicken was assessed and characterization of these strains was conducted. Meanwhile, the inhibition effect and mechnisms of tannin-rich fraction from pomegranate rind(TFPR) on E. coli biofilm formation were studied. It is expected that these findings will provide theoretical bases for developing a safe antibacterial agent. The main results are as follows:(1) Among all the 117 E. coli isolates from retail chicken in Beijing, 92 of them(78.63%) were strong biofilm producer, and the reset 25 isolates(21.37%) were weak biofilm producer. In 35 randomly selected isolates, there is no correlation between minimum inhibitory concentration of benzalkonium chloride(BAC) and specific biofilm formation index, while lies a significant positive correlation between minimal biofilm eradication concentration and specific biofilm formation index. Only fimA、hlyA and tsh genes were found to be correlated with strong/weak biofilm formation producers.(2) Biofilm formation and motility of E. coli were hindered by TFPR. Transcriptional analysis further showed that TFPR repressed expressions of curli genes(csgB and csgD) and various motility genes(fimA, fimH, flhD, motB, qseB, and qseC).(3) It was shown that TFPR inhibited violacein pigment production of AI-1 quorum sensing indicator strain, Chromobacterium violaceum. For the precdicted molecular docking test, it was also shown that ellagic acid, a component of TFPR, had potency to attenuate quorum sensing of E. coli.