Detection ofBifidobacterium longumin faecal samples after orogastric intubation using immunological test systems

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Abstract
A simple method based on a sandwich-ELISA was developed to study the passage and the viability of a bifidobacterial species after oral application of lyophilized preparation. Rabbits were immunized with a formaldehyde-inactivated strain of the species Bifidobacterium longum resulting in a highly specific antiserum. The cross-reaction of most of 46 selected, representative strains of 14 bifidobacterial species from animal and human sources was negligibly low. Only two strains of B. angulatum and some strains of B. longum isolated from breast-fed infants showed cross-reactions greater than 10 per cent, which was not reflected by biochemical characteristics such as murein type and DNA-DNA homology grouping. Western blot analyses indicated a 60-KDa protein as the major immunogen of the strain used for the immunization procedure. The detection limit of the sandwich-ELISA developed on the basis of the antiserum was about 103 cells/ml test buffer. Viable B. longum could be detected strain specifically in faeces of minipigs after oral application of a pharmaceutical product containing B. longum and two additional non-bifidobacterial species. The viable B. longum was determined by a combination of selective cultivation from faecal samples and immunological techniques based on the specific anti-B. longum antibody.