Biochemical characterization of different types of adherence of Vibrio species to fish epithelial cells.

Vibrio species are Gram-negative bacteria that cause a systemic infection in fish called vibriosis. The authors previously demonstrated that internalization and cytotoxicity are important virulence mechanisms in vibrio-fish epithelial cell interactions. Adherence is a prerequisite for successful internalization. In this study, the adherence capability of two invasive strains [V. anguillarum 811218-5W and G/Virus/5(3)] was compared with that of two non-invasive strains [V. damselae ATCC 33539 and V. anguillarum S2/5/93(2)] using adherence assays in three different types of fish cells (epithelial papillosum of carp, EPC; grunt-fin tissue, GF; and fat-head minnow epithelial cells, FHM). For all four strains there was no significant difference (P>0.05) in the adherence to the different cell lines. V. anguillarum 811218-5W exhibited the highest adherence, followed by G/Virus/5(3) and S2/5/93(2); V. damselae ATCC 33539 showed the lowest adherence. The super-adherence characteristic of V. anguillarum 811218-5W on EPC cells was not affected by inhibitors, sugars, low temperature (4 degrees C) incubation, or non-biological surfaces such as glass coverslips. The galactose-linked adherence characteristic of V. anguillarum G/Virus/5(3) to the EPC cells was partially inhibited by peptidase treatment of the fish cells, low-temperature incubation, and addition of sugars that contained galactose (such as lactose and N-acetyl-D-galactosamine). De novo synthesis of bacterial protein, viable bacteria and intact carbohydrate structure of vibrios were required for both super-adherence and galactose-linked adherence. These adherence characteristics were also found in ten other invasive vibrios, and galactose-linked adherence was found in nine invasive vibrios.