Enumeration and identification of Lactobacillus paracasei subsp. paracasei F19

The identification of probiotic lactobacilli at strain level is important for their industrial use. Methods for enumeration and identification of Lactobacillus paracasei subsp. paracasei isolate F19 ( Lactobacillus F19) were evaluated. Nine closely related isolates were used to validate the methods. MRS with vancomycin (20 &#119 g ml) or adjusted to pH 5.4, and Rogosa with vancomycin (20 &#119 g ml) showed good results for enumeration in dairy products and biological samples, respectively. MRS with cefotaxime (0.5-2 &#119 g ml) slightly suppressed growth and cell count of Lactobacillus F19. RAPD analysis modified from the study by Tynkkynen et al. (1999) proved applicable for strain-level identification of Lactobacillus F19. Also, FT-IR analysis was tested with good results. The recommendation is to enumerate using the MRS with vancomycin or adjusted to pH 5.4 and screen colonies with RAPD analysis with the primer Lbc-19 and confirm identity with the primer OPA-02, provided that the preparation of crude cell extracts and the parameters of RAPD protocol are strictly standardized.