Bifidobacterial Diversity and the Development of New Microbial Source Tracking Indicators
ABSTRACTMany studies suggest a close relationship between species ofBifidobacteriumand their hosts. Thus, species such asB. adolescentisandB. thermacidophilumsubsp.porcinumhave been proposed as potential indicators of human and porcine fecal pollution. The diversity of bifidobacteria in wastewaters (human and animal) and slurries is analyzed using nested PCR followed by denaturant gradient gel electrophoresis (DGGE). The sewage samples showed similar DGGE patterns. The predominant bands were recognized asB. adolescentis,B. longum, and two unidentified species related toB. adolescentis. A single band detected in poultry samples was identified asB. saeculare. Bifidobacterial diversity was higher within porcine and bovine samples. The main bands in porcine samples were identified asB. minimum, an unknown species, andB. thermophilum/B. thermacidophilumsubsp.porcinum. The latter species was also identified among the main bands in bovine samples together withB. pseudolongumandB. ruminantium. We then attempted to isolate the host-specific strains. DGGE bands were examined to develop specific probes to screen environmental samples by colony hybridization and further isolation of strains from positively hybridized colonies. Bifidobacterial strains that are host associated by DGGE bands to human and pig were successfully isolated from the environment:B. adolescentisfrom human sewage samples and the unidentified species related to pig from slurries and slaughterhouse wastewater. Neither the poultry-associatedB. saecularenor the ruminant-associatedB. pseudolongumcould be isolated with the current methodology, suggesting either a low prevalence in the samples or failure of the culture to grow in the media used.