Specific identification and molecular typing analysis of Lactobacillus johnsonii by using PCR-based methods and pulsed-field gel electrophoresis.

A fast and reliable Multiplex-PCR assay was established to identify the species Lactobacillus johnsonii. Two opposing rRNA gene-targeted primers have been designed for this specific PCR detection. Specificity was verified with DNA samples isolated from different lactic acid bacteria. Out of 47 Lactobacillus strains isolated from different environments, 16 were identified as L. johnsonii by PCR. The same set of strains was investigated with five alternative molecular typing methods: enterobacterial repetitive intergenic consensus PCR (ERIC-PCR), repetitive extragenic palindromic PCR (REP-PCR), amplified fragment length polymorphism, single triplicate arbitrarily primed PCR, and pulsed-field gel electrophoresis in order to compare the discriminatory power of these methods. The reported data strongly support the highly significant heterogeneity among all L. johnsonii isolates, potentially linked to their origin of isolation. The use of species-specific primers as well as rapid and highly powerful PCR-based molecular typing tools (namely ERIC- and REP-PCR techniques) should be respectively envisaged for identifying, differentiating and monitoring L. johnsonii strains from various environmental samples, for product monitoring, for species tracing in clinical studies as well as bacterial profiling of various microecological or gastrointestinal environments.