In vitro biofilm forming capacity on abiotic contact surfaces by outbreak-associated Vibrio harveyi strains

Objective:To evaluate the in vitro biofilm forming capacity on abiotic food contact surfaces by Vibrio harveyi(V.harveyi)strains.Methods:Thirty six Gram-negative V.harveyi strains were isolated from various street vended seafood outlets in a food processing line and evaluated for their ability to produce mucoid biofilms on food contact surfaces using a microplate assay.Phenotypic characterization of mucoid biofilm producing V.harveyi strains were screened on Congo red agar,thiosulfate-citrate-bile salts-sucrose agar and tryptic soy agar,respectively.Results:Only five V.harveyi strains(14%)were mucoid biofilm producers characterized by formation of black colonies,whereas the remaining 31 strains(86%)were not capable of producing biofilm characterized by formation of red colonies or pinkish-red colonies with darkening at the centre.The morphological,physiological and biochemical characteristics of these isolates were studied using standard protocols.Strain identification was confirmed by polymerase chain reaction targeted to species-specific polymerase chain reaction primers VH-1 and VH-2 corresponding to variable regions of V.harveyi 16S rRNA sequence.All the biofilm-forming strains showed resistance to at least three antimicrobial compounds tested.V.harveyi strains isolated from various seafood were able to form biofilms of different capacity,and the strains VB267,VB238 and VB166 isolated from cat fish,shrimp and eel fish exhibited significantly greater biofilm forming ability compared to other isolates.Conclusions:It can be concluded from the present study that the strain VB166 was able to better attach and form subsequent biofilms on glass and stainless steel compared to high density polyethylene.These properties allow these bacteria to survive,proliferate and persist in street vended seafood outlets.