Inhibitory effects of lactobionic acid on Vibrio parahaemolyticus planktonic cells and biofilms

Vibrio parahaemolyticus is the primary pathogenic bacteria associated with seafood-borne illnesses. Lactobionic acid (LBA) is an organic acid with multiple biological activities that has recently been a focus of interest as an antibacterial agent. The aim of this study was to investigate the inhibitory effects of LBA on Vibrio parahaemolyticus planktonic cells and biofilms. The minimum inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of LBA against Vibrio parahaemolyticus were both identified as 4 mg/mL. LBA exerted antimicrobial effects against planktonic Vibrio parahaemolyticus cells by damaging their membranes, as revealed by reduced intracellular ATP concentrations, increased protein leakage, abnormal cell morphology and diminished membrane integrity after treatment. At 1/16 × MIC and 1/8 × MIC, LBA inhibited biofilm formation and downregulated the expression of some biofilm-related genes, which was confirmed by crystal violet staining, field-emission scanning electron microscopy (FESEM) observations, and real-time quantitative PCR analysis. Moreover, LBA inactivated Vibrio parahaemolyticus cells within biofilms (on polystyrene and stainless steel surfaces), destroyed biofilm structures on stainless steel surfaces, and also reduced the levels of polysaccharides and proteins in the biofilms. Therefore, LBA is a potential low-cost agent that can be used to control planktonic Vibrio parahaemolyticus and its biofilms.