Antimicrobial action of some GRAS compounds against Vibrio vulnificus

Vibrio vulnificus is a bacterium indigenous to estuarine waters and is known to be a significant human pathogen. Infections are generally associated with the consumption of raw oyster. In an attempt to identify possible antimicrobial agents against this organism that might be used in foods, ten compounds that are generally recognized as safe (GRAS) by the FDA were tested against both the opaque and translucent morphotypes of V. vulnificus. Eight of those compounds had a lethal effect for both morphotypes of this bacterium. Diacetyl had the lowest lethal concentration (50 ppm) of the GRAS compounds tested within 24 h. Lactic acid and butylated hydroxyanisole possessed lethal activities at 300 ppm and 400 ppm, respectively, within 3 h. The mode of action of lactic acid against V. vulnificus appears to be an effect primarily of pH, while the antimicrobial activities of diacetyl and BHA appeared not to be affected by pH. No significant differences were found for opaque to translucent, or from translucent to opaque switching, in examining the possible effects of the GRAS compounds on colonial morphology.