Isolation of bifidobacteria from food and human faeces and rapid identification by Fourier transform infrared spectroscopy

Bifidobacteria are suggested to include a number of probiotic species which are added to dairy products. A total of 67 Bifidobacterium strains were isolated from food stuff and human faeces and were identified by fermentation tests and, in many cases, by 16S rDNA sequencing. In food products, only B. animalis was found. B. longum was present in starter cultures, but not in dairy products. B. bifidum, B. pseudocatenulatum, B. longum/infantis, B. breve, and B. dentium were isolated from faeces of infants and adults. The identification of the species of this genus by physiological methods is time consuming (seven days, starting from purified colonies) while molecular identification methods are rapid, but quite expensive. Therefore, we tested Fourier transform infrared (FT-IR) spectroscopy, an emerging physicochemical identification method, which correctly identified 62 out of the 67 isolates within two days. With respect to the overall cellular composition, which is the basis of FT-IR spectroscopy, the type strains of B. bifidum, B. breve and B. infantis appear to be rather untypical and did not cluster near the isolates of these species. The discrimination between B. infantis and B. longum as well as between B. lactis and B. animalis was difficult with all methods applied.