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A polymerase chain reaction (PCR)-based method was developed for the identification of isolates of Bifidobacterium at the species level. Using two Bifidobacterium-specific primers directed against the 16S ribosomal gene (Bif164 and Bif662), a PCR product was obtained from the type strains of 12 different bifidobacterial species that have been found in the human alimentary tract. After purification of the PCR products, the DNA was restricted with five different restriction enzymes. The size of the different restriction fragments was used as a fingerprint for the identification of individual bifidobacterial species. The amplified ribosomal DNA restriction analysis method was subsequently used to speciate bifidobacterial isolates from child's feces and from an in vitro model of the large intestine.

A validated in vitro model of the large intestine ( TIM-2), set up with human or pig faeces, was used to evaluate the impact of potentially probiotic Lactobacillus amylovorus DSM 16698, administered alone (i), in the presence of prebiotic galactooligosaccharides ( GOS) (ii), and co-administered with probiotic Bifidobacterium animalis ssp. lactis Bb-12 ( Bb-12) (iii) on GOS degradation, microbial growth ( L. amylovorus, lactobacilli, bifidobacteria and total bacteria) and metabolite production. High performance anion exchange chromatography revealed that GOS degradation was more pronounced in TIM-2 inoculated with pig faeces than with human faeces. Denaturing gradient gel electrophoresis profiling of PCR-amplified 16S r RNA genes detected a more complex Lactobacillus spp. community in pig faecal material than in human faecal inoculum. According to 16S r RNA gene-targeted q PCR, GOS stimulated the growth of lactobacilli and bifidobacteria in faecal material from both materials. The cumulative production of short chain fatty acids and ammonia was higher ( P < 0.05) for pig than for human faeces. However, lactate accumulation was higher ( P < 0.05) in the human model and increased after co-administration with GOS and Bb-12. This study reinforced the notion that differences in microbiota composition between target host organisms need to be considered when animal data are extrapolated to human, as is often done with pre- and probiotic intervention studies. [ABSTRACT FROM AUTHOR]