Selective enumeration of dairy based strains of probiotic and lactic acid bacteria

Reliable methods for selective enumeration of probiotic and lactic acid bacteria (LAB) are required for improving the functional food quality of probiotics. Various methods were evaluated for selective enumeration of seventeen LAB and probiotic strains. Tested sugars failed to select any species however, improved recovery of total LAB count. The strains were viable and physiologically active within a range of oxygen tension levels, temperature and acidic conditions. Prior methods showed varied results such as De Man Rogosa Sharpe containing bile (MRSB), MRS containing nalidixic acid, paromomycin, neomycin sulphate and lithium chloride (MRS-NPNL), M17 and L. casei (LC) agar failed to select Lactobacillus acidophilus, Bifidobacterium, starter LAB and L. casei strains respectively. However, LC agar appears appropriate for L. paracasei and MRSB for yoghurt starter bacteria in the absence of L. reuteri and L. rhamnosus. The study suggests selective potential of culture media largely depends on target species.