Inhibition of the in vitro growth of Salmonella enteritidis D by goat and cow milk fermented with probiotic bacteria Bifidobacterium longum Bb-46

Abstract

This study was carried out to determine the influence of goat and cow milk fermented by <I>Bifidobacterium longum</I> Bb-46 on the pathogenic <I>Salmonella enteritidis</I> D strain. The basic hypothesis of this study was that fermented goat milk could possibly have a stronger inhibitory effect on the growth of <I>Salmonella enteritidis</I> D than fermented cow milk. The correlation between the inhibitory effect and some fermentation parameters (number of viable cells of <I>Bifidobacterium longum</I> Bb-46 and pH of fermented milk) was also analysed. <I>S enteritidis</I> D strains were isolated directly from the faeces of an infant with diagnosed salmonellosis. The inhibitory effects of goat and cow milk fermented with <I>Bifidobacterium longum</I> Bb-46 were determined on Salmonella-Shigella agar after 0, 5, 10, 15, 20, and 25 h from the start of fermentation. <I>Bifidobacterium longum</I> Bb-46 count and pH values were also measured in samples of goat and cow milk during fermentation. The results obtained have shown a considerably higher inhibitory effect of fermented goat milk on the growth of <I>Salmonella enteritidis</I> D as compared to that of fermented cow milk. At the same time, higher acidity and CFU of <I>Bifidobacterium longum</I> Bb-46 were noted in fermented goat milk in all the phases of the fermentation process. The inhibitory effects of the fermented goat and cow milk on <I>Salmonella enteritidis</I> D growth increased rapidly with the fermentation time. The results indicated high sensitivity of <I>Salmonella enteritidis</I> D to acidity of both fermented milks. Consequently, a significant correlation between the inhibition degree and pH values of fermented goat and cow milk was noted.