Assessment of the anti-biofilm activity of traditional homemade prickly pear vinegar against selected food-borne pathogens on different abiotic surfaces

Samia AZABOU, Mouna BEN HAMMOUDA, Hamadi ATTIA

Laboratoire Analyse, Valorisation et Sécurité des Aliments, ENIS, Université de Sfax, 3038, Tunisie
*azabousamia@yahoo.fr

Background : One of the most worldwide public concerns facing various food industries is the microbial food-borne disease mainly attributed to biofilms, that account for up to 80% of microbial infections. Biofilms have become a real problem in food industries such as brewing, seafood, dairy, poultry, and meat processing, because they make their inhabitants resistant to antimicrobial agents and cleaning processes. Numerous approaches have been used for biofilm prevention and removal such as, flushing, chlorination, and ultraviolet disinfection. However, these methods lack both effectiveness and safety, and therefore, the development of new and natural anti-biofilm agents seems to be interesting, given that the emergence of antibiotic-resistant bacterial strains as well as the consumer attitude towards the consumption of chemically treated food products have encouraged researchers to find effective alternatives and develop natural antimicrobial agents.

Objectives: To evaluate the antibacterial and anti-biofilm activities of traditional homemade prickly pear vinegar (PPV) against selected food-borne pathogens on different abiotic surfaces.

Methods: Minimum inhibitory (MIC) and bactericidal (MBC) concentrations assays were carried out using the two-fold serial dilution method and MTT assay against Gram-positive (Staphylococcus aureus CIP 4.83) and Gram-negative (Escherichia coli CIP 54127 and Salmonella enterica CIP 8297) bacterial strains. The biofilm inhibitory effect of traditional PPV on initial cell attachment and mature microbial biofilms was investigated on three abiotic surfaces viz., polystyrene microplates, stainless steel and glass slides.

Results: Obtained results demonstrated that homemade PPV could be an effective antimicrobial agent against both sessile and planktonic cells of S. aureus, E. coli, and S. enterica. PPV was found to be more effective in inhibiting initial cell attachment compared to 24h-preformed biofilms. Besides, it was efficient to reduce the metabolic activity of the tested biofilm-forming bacteria. The anti-biofilm effect of homemade PPV was evaluated on two additional abiotic surfaces such as glass and stainless steel surfaces, commonly encountered in food processing environments. Results showed that treatment of the studied biofilms with PPV at 2×MIC (% v/v) resulted in a log reduction of the initial biomass. Microscopic analysis on glass surface confirmed PPV inhibitive effect, where a reduction in the dispersed cells was observed.

Conclusion: These findings suggested that homemade PPV could be used as a natural and safe antimicrobial and anti-biofilm agent against food-borne pathogens encountered in the agri-food industries.