Bifidus-Blood Agar a Differentiatin Medium for Isolation and Enumeration of Bifidobacteria from Faecal Samples
Bioscience and Microflora
A modification of bifidus-blood agar (A-W) containing peptones combination "A" (peptone from casein trypsin digested, peptone from meat pepsin digested, peptone from meat trypsin digested) and water-soluble aniline blue "W" was evaluated for its use in enumeration of Bifidobacterium species in faeces. This medium was originally described by Reuter in 1963. Colonies of bifidobacteria appeared copper coloured and had an elevated morphology on bifidus-blood agar (A-W). This distinct appearance
... wed an easy and quick differentiation of bifidobacteria in faecal samples. Using bifidus-blood agar (A-W), bifidobacteria were isolated from 24 mouse faecal samples (n = 26), 16 human faecal samples (n =16), and two rat faecal samples (n = 3). Ten known strains of Bifidobacterium and 50 strains of Bifidobacterium species isolated from faecal samples and commercial products all grew as elevated, copper colonies on bifidus-blood agar (A-W). Colonies of lactobacilli were distinctly different in colour and morphology, as were all other faecal bacteria in the samples tested. When recovery of bifidobacteria on bifidus-blood agar (A-W) was compared with that on three non-selective and two selective media, the recovery on bifidus-blood agar (A-W) was equivalent to that of two of the non-selective media. However, A-W agar provided a significantly higher recovery than the third non-selective medium and both selective media tested. The method of preparation and the choice of ingredients used were important.