Inhibition of Escherichia coli O157:H7 and Salmonella enterica virulence factors by benzyl isothiocyanate

Authors: Patel, Jitu; YIN, HSIN-BAI - UNIVERSITY OF MARYLAND; Bauchan, Gary; MOWERY, JOSEPH

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2019
Publication Date: 4/20/2020
Citation: Patel, J.R., Yin, H., Bauchan, G.R., Mowery, J.D. 2020. Inhibition of Escherichia coli O157:H7 and Salmonella enterica virulence factors by benzyl isothiocyanate. Food Microbiology. https://doi.org/10.1016/j.fm.2019.103303.
DOI: https://doi.org/10.1016/j.fm.2019.103303

Interpretive Summary: Benzyl isothiocyanate (BIT) is a naturally occurring glucosinolate-hydrolysis compound commonly found in cruciferous vegetables. The antimicrobial activity glucosinolate-hydrolysis compounds against plant pathogens have been documented. We evaluated the antimicrobial and anti-virulence activity of BIT against foodborne pathogens: Escherichia coli O157:H7 and Salmonella. Confocal microscopy and transmission electron microscopy (TEM) procedures were used to determine bacterial damage at the cellular level. Results revealed that BIT at very low concentrations significantly inhibited the motility of both Salmonella and E. coli O157:H7. Shiga toxins produced by E. coli O157:H7 which may damage kidney was decreased by at least 18% and 32% in the presence of BIT at 0.0125% and 0.015%, respectively. TEM results showed the disruption of outer membrane, release of cytoplasmic contents, and cell lysis following BIT treatment. The BIT could be potentially used as an ingredient of salad dressings to serve as therapeutic interventions by reducing the virulence factors responsible for human illnesses. This research benefits processors in potential intervention against bacterial pathogens in fresh produce processing.

Technical Abstract: Escherichia coli O157:H7 and Salmonella spp. are foodborne pathogens with major public health concern in the United States. These bacterial pathogens utilize several virulence factors to initiate infections in human hosts and subsequently cause diseases. Bacterial motility helps in initial stages of infection whereas shiga toxins produced by E. coli O157:H7 may cause kidney failure in humans. The antimicrobial effect of seven glucosinolate hydrolysis compounds against Salmonella and E. coli O157:H7 was investigated by disc diffusion assay. Benzyl isothiocyanate (BIT), a glucosinolate hydrolysis compound with the highest antimicrobial activity, was evaluated for its effects against E. coli O157:H7 and Salmonella virulence in vitro. The effect of BIT on motility of Salmonella and E. coli O157:H7 and shiga toxin production by E. coli O157:H7 was determined by the motility assay and ELISA procedure, respectively. Confocal microscopy and transmission electron microscopy (TEM) procedures were used to determine bacterial damage at the cellular level. Results revealed that sub-inhibitory concentrations (SICs) of BIT significantly inhibited the motility of both Salmonella and E. coli O157:H7 (P<0.05). Shiga toxin production by E. coli O157:H7 was decreased by at least 18% and 32% in the presence of BIT at 0.0125% and 0.015% (SIC), respectively. TEM results showed the disruption of outer membrane, release of cytoplasmic contents, and cell lysis following BIT treatment. The results of current study suggest that BIT could be potentially used to attenuate Salmonella and E. coli O157:H7 infections by reducing the virulence factors including bacterial motility and shiga toxin production.