A selective medium for isolation and accurate enumeration of Lactobacillus casei-group lactobacilli in probiotic milks and dairy products

The correct identification and quantitative detection of Lactobacillus casei-group members continues to be a key issue due to the extensive use of members of this group as (probiotic) adjuncts, corrective and/or reinforcement cultures. Numerous selective/differential media use selective agents to which injured or stressed cells are sensitive, resulting in an underestimation of the actual number of target bacteria. We developed a selective medium and applied it to detect members of the Lb. casei-group reliably, regardless of their physiological condition, quantitatively detect and isolate strains of this group from probiotic milk and cheeses, and monitor the probiotic Lb. paracasei CRL 431 strain in Caciotta cheeses made either from goats' or cows' milk inoculated with this probiotic strain and a multiple strain culture. This approach could be useful for control bodies, agro-food and pharmaceutical industries to isolate Lb. casei-group strains, develop probiotic food/supplements and demonstrate their compliance with the species labelling.