Quantification of Lactobacillus gasseri, Enterococcus faecium and Bifidobacterium infantis in a probiotic OTC drug by real-time PCR

Application of real-time PCR and SYBR Green for selective enumeration of probiotic bacteria in a lyophilised probiotic product sold as an OTC drug, containing Lactobacillus gasseri, Bifidobacterium infantis and Enterococcus faecium was evaluated. Maxwell DNA Purification Kit was found the most efficient and repeatable. Among nine pairs of primers tested, the following were selected: Enc-F, Enc-R for E. faecium, Lgas-3/Lgas-2 for L. gasseri and BiINF-1/BiINF-2 for B. infantis. Comparison of plate counts and real-time PCR analysis of 10 batches of product showed that on average 62% of lactobacilli, 45% of enterococci and 2% of bifidobacteria preserved their culturability.