Wine is bactericidal to foodborne pathogens

Summary

Red and white wines without added sulfite were tested for antibacterial activity against stationary-phase grown cells of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus. The wines had bactericidal activity against all strains, with the red wine being most potent. S. Typhimurium was most sensitive, with 6 log reduction after 10 min exposure to wine, whereas S. aureus appeared least sensitive to the wines. Mutants having the gene encoding the alternative sigma factor disrupted were generally more sensitive to wine than their wild-type counterparts. When different combinations of ethanol, organic acids, and acidity were tested against the pathogens, it was found that a composition of 0.15% malic acid, 0.6% tartaric acid, 15% ethanol, and pH 3.0 had a strong bactericidal effect. The compounds in the mixture seemed to act synergistically against the pathogens. The pathogens grew in 25% to 40% white wine diluted in brain hearth infusion broth, with S. aureus being able to grow at the highest concentration of wine. Preincubation of the bacteria in sublethal concentrations of wine and ethanol and pH 4.5 did not increase their tolerance against wine or against the mixture of organic acids and ethanol. In conclusion, wine had an antibacterial effect against the pathogens tested. The synergistic effect of organic acids, ethanol, and low pH seems to be responsible for a major part of the antibacterial effect of wine. The alternative sigma factors seemed to be involved in protection of the bacteria against wine.