Bile salt hydrolase activity of Enterococci isolated from food: screening and quantitative determination

One hundred seventeen enterococcal strains isolated from food (47 Enterococcus faecium, 48 Enterococcus faecalis, 16 Enterococcus durans, 2 Enterococcus gallinarum, 3 Enterococcus casseliflavus, and 1 Enterococcus malodoratus) were screened for bile salt hydrolase (BSH) activity on de Man, Rogosa, and Sharpe agar medium containing taurocholic acid and calcium chloride. The highest incidence of BSH-active strains was observed for E. faecalis (81%) followed by E. faecium (50%) and E. durans (44%). Isolates were grouped into four putative activity groups (no, low, medium, and high activity) based on the size of precipitation zones observed in the screening experiment. Our results showed that assumptions on BSH activity based on the size of bile precipitation zones in screening experiments did not correlate with actual activity as quantified by high-pressure liquid chromatography, but the screening assay is useful for assessing the presence or absence of BSH activity.