The composition and diversity of the gut microbiota are known to be different between babies and adults. The
aim of this project was to compare the level of bifidobacteria between babies and adults and to investigate
the influence of lifestyle factors on the level of this bacterium in the gut. During this study, the levels of
bifidobacteria in 10 human babies below 2 years of age were compared with that of 10 human adults above 40
years. The level of bifidobacteria proved to be significantly higher in babies in comparison with adults. This
investigation concluded that a combination of several factors, such as age, diet, and BMI, has an important
effect on the level of bifidobacteria in adults, while in babies, a combination of diet and age may influence
the level of intestinal bifidobacteria.
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 allowed 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.
The potential of six strains of Bifidobacterium to colonise the gastrointestinal (GI) tract of Swiss mice , their interaction i n the GI tract of Swiss mice and their in-vitro characteristics were investigated. This study revealed that a strain of Bifidobacterium that was isolated from a C57BL/10 ScSn mouse was capable of colonising the GI tract of Swiss mice and remaining there for at least one month. The in-vitro studies showed that this strain had the highest capability among the six strains to adhere to the intestinal tissue of BALB/c mice. This strain grew in presence of 2% bile and lost less than 10-fold viability at pH 2.5.
This work was carried out in collaboration between all authors. Author OSF designed the study performed the test, performed the statistical analysis, wrote the protocol, wrote the first draft of the manuscript and managed literature searches. Author SS also performed the test. Author AP supervised the test. Authors AOM and OAM performed the statistical analysis. All authors read and approved the final manuscript.
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