Jose M. Miranda, Fabiao Jorge, Lucas Dominguez, Alberto Cepeda, Carlos M. Franco

Laboratorio de Higiene, Inspección y Control de los Alimentos. Dpto. de Química Analítica, Nutrición y Bromatología. Facultad de Veterinaria, Universidad de Santiago de Compostela, 27002, Lugo, Spain.

Abstract

The study investigates the effectiveness of a synthetic vitamin analog (vitamin k₅) for the growth inhibition of a total of 14 bacterial pathogens, spoilage-inducing bacteria and three spoilage-inducing molds that were tested during this study. Bacterial growth inhibition by vitamin k₅ and vitamin k₅ combined with sodium chloride (NaCl) were tested by determining the Minimum Inhibitory Concentrations (MICs) using a broth microdilution method. Antifungal effects of vitamin k₅ were determined by measuring the growth of three different spoilage molds on Malt agar plates containing different concentrations of vitamin k₅. All bacterial strains assayed were inhibited by vitamin k₅ in a range of 64-1,024 μg/ml. When vitamin k₅ was combined with 3% NaCl, five out of the 14 bacterial strains assayed showed lower MICs than for vitamin k₅ alone. When vitamin k₅ was combined with 5% NaCl, nine of the 14 bacterial strains assayed displayed lower MICs than for vitamin k₅ alone. With respect to inhibition of molds, 10 μg/ml vitamin k₅ induced inhibitory effects against Aspergillus parasiticus NRRL 2999 and Penicillium expansum NRRL 6069, but not Aspergillus flavus NRRL 6540. In contrast, 30 or 50 μg/ml vitamin k₅ showed inhibitory effects against the growth of all molds assayed; however, inhibitory effects against aflatoxin production by A. flavus NRRL 6540 were achieved only with 50 μg/ml. These data show that vitamin k₅ is a useful antimicrobial agent that at low concentrations causes growth inhibition of a broad spectrum of bacterial pathogens and spoilage bacteria as well as certain molds.