Vibrio vulnificus is a foodborne pathogen causing septicemia with high mortality rate. In this study, we explored how Escherichia coli, one of the commensal bacteria in the human gastrointestinal tract, can interact with V. vulnificus. Our study results show that the amount of biofilm produced by V. vulnificus was reduced in the presence of E. coli ATCC 35218, although the growth of V. vulnificus L‐180 remained unaffected. We also detected an antibiofilm effect of E. coli culture supernatant against V. vulnificus, which could not be reduced even after heat treatment. These findings indicate that E. coli and its culture supernatant may be suitable to prevent biofilm formation by V. vulnificus. By contrast, live cells of V. vulnificus could reduce the amount of preformed E. coli biofilm, but its culture supernatant could not. This suggests that the cell‐associated factors contribute toward reduction in E. coli biofilm. Therefore, we speculate that ingestion of an infectious dose of V. vulnificus might induce dislodging of the commensal bacteria from the intestinal epithelia and thus can colonize to initiate the infection.

About 60 tonnes of food pass through human gastrointestinal (GI) tract through an average lifetime together with many environmental microorganisms contaminating the food. These microorganisms might pose threat on GI tract integrity (Bengmark, 1998) or may colonize the GI tract and serve as a source for spreading perilous microorganisms, such as antibiotic resistance bacteria, to other individuals or to the environment (Boyee et al., 2007) . The gut microbiota is the term used to refer to all bacteria, archaea and eukarya living in the GI tract. Balance between the GI tract microbiota is important for maintaining host health, so that, distortion of this balance has been hypothesized to be involved in various diseases such as inflammatory bowel diseases, diabetes and others (Gu et al., 2013) .Colonization resistance is the mechanism whereby the intestinal microbiota protects itself against invasion by new and potentially harmful microorganisms. Colonization resistance can occur through direct or indirect manner (Buffie and Pamer, 2013) . In the first form, the commensals compete with invading microorganisms for available nutrient and niche establishment or through production of antimicrobial peptides and/or toxins against the invaders. Indirect colonization resistance is derived from stimulation of host innate and adaptive immune response by commensals against the invaders (Sassone- Corsi and Raffatellu, 2015) .Escherichia coli is a gram-negative motile bacterium and a commensal bacterium found commonly in the large intestine of human and animals (Poulsen et al., 1994) . Staphylococcus epidermidis is a gram-positive non-motile bacterium belonging to the coagulase negative staphylococci. This bacterium is widely present in the cutaneous ecosystem but linked to medical device associated nosocomial infections (von Eiff et al., 2002) . However, S. epidermidis is also a prominent coagulase negative bacteria recovered from the GI tract of children (Dominguez et al., 2002) . Namely, Akikumi and Lamikanra (2010) reported the recovery of drug resistant S. epidermidis strains from the GI tract of children, and Ohno et al. (2007) documented that 22.3 % of hospitalized pediatric children were carriers of methicillin resistant S. epidermidis strains. These studies suggest