[Show abstract][Hide abstract] ABSTRACT: The diversity of 87 Lactobacillus paracasei and Lactobacillus plantarum/paraplantarum strains, pre-viously identified from different autochthonous dairy products, was investigated by phenotypic and genotypic approaches. The increased resolution obtained using phe-notypic and genotypic characterization allowed the level of strain heterogeneity detection to be widened. Phenotypic diversity was evaluated by studying biochemical charac-teristics of technological interest, including antimicrobial and proteinase activities, resistance to nisin, aggregation ability, production of exopolysaccharides, acetoin and diacetyl, citrate utilization, and antibiotic susceptibility. Genotypic diversity was generally evaluated by PCR amplification of repetitive bacterial DNA element finger-printing using the (GTG) 5 primer [(GTG) 5 -PCR]. More-over, in cases where strains were not discriminated by (GTG) 5 -PCR combined with phenotypic analysis, pulsed-field gel electrophoresis (PFGE) analysis was performed. The results indicate that L. plantarum/paraplantarum and L. paracasei natural isolates from artisanal dairy products are a gold mine in terms of diversity of strains and could be potentially interesting to dairy companies for the formu-lation of functional starter cultures in the production of innovative foods.
Full-text · Article · Apr 2012 · European Food Research and Technology
[Show abstract][Hide abstract] ABSTRACT: Listeria monocytogenes is a facultative intracellular Gram-positive bacterium, ubiquitous in nature and capable of causing listeriosis in humans and animals. Conventional microbiological techniques and modern molecular approaches are currently used for the isolation and detection of L. monocytogenes in food samples. The aim of this study was to improve the sensitivity and reproducibility of PCR for the detection of Listeria spp. in milk. For that purpose milk samples were artificially inoculated with serial dilutions of L. monocytogenes 4b ATCC 19115 and L. innocua ATCC 33090. The results obtained on artificially contaminated milk samples indicated that incubation time and target genes have an influence on the sensitivity of PCR detection. The best results were obtained after 24 h of pre-enrichment, with primers complementary to the hlyA gene, when it was possible to detect 1 CFU/mL of Listeria spp.