Historically, wine was believed to aid digestion, and recently consumption of alcohol has been reported to have a protective effect during foodborne outbreaks of Salmonella Enteriditis and hepatitis A. The consumption of alcohol has also been shown to protect against Helicobacter pylori, which is a major cause of respiratory tract infections.

The precise mechanisms responsible for the antibacterial effects of wine are not fully understood. Wine contains several compounds with antimicrobial activity such as malic and tartaric acids and ethanol. In addition, the low pH and presence of polyphenols may contribute to the antimicrobial effects.

When bacteria are exposed to environmental stress, they may initiate a response to the new conditions. Several of the components present in wine, such as ethanol and organic acids, and a low pH may induce stress responses in several genera of bacteria. The expression of genes involved in stress response are often controlled by alternative sigma factors. Sigma mutants impaired in their ability to launch stress responses have been found to be more sensitive than their wild counterparts to stresses such as ethanol, low pH and antibiotics,

A study by Moretro and Daeschel¹ evaluated the antibacterial effect of red and white wines, without added sulfite, against wild-type strains and sigma mutants of the pathogenic bacteria E. coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes and Staphyloccus aureus. The wines exhibited antibacterial effects against these pathogens, with synergism between organic acids, low pH and ethanol appearing to be responsible for a major part of this activity. The alternative sigma factors seemed to be involved in protecting the bacteria against wine.
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¹ Moretro, I; Daeschel, MA (2004). Wine is bactericidal to foodborne pathogens. Journal of Food Science 69 (9) 251-257.

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