Bifidobacterium species isolated from animal feces and from beef and pork meat

Abstract

Bifidobacteria were isolated from 122 of 145 samples of animal feces (from cattle, swine, sheep, goats, horses, rabbits, chickens, geese, and pigeons) from farms in France and Austria and from 92 of 955 production and processing chain samples of beef and pork (obtained at slaughter, cutting, and retail). Bacterial strains were identified to species by phenotypic numerical classification based on API 50CH and ID 32A tests and DNA-DNA hybridization. Bifidobacterium pseudolongum was present in 81% (99 of 122 samples) of all Bifidobacterium-positive fecal samples and predominated in samples from all animal species except those from swine from Austria. In these Austrian swine samples, the majority of strains were identified as Bifidobacterium thermophilum (78%), followed by B. pseudolongum (48%). The distribution of B. thermophilum and B. pseudolongum differed significantly between Austrian swine and cattle samples such as those collected along beef and pork production and processing chains. Bifidobacterium animalis was isolated from swine feces, and Bifidobacterium ruminantium was isolated from cow dung. Six fecal isolates (from cattle, swine, rabbits, goats, and horses) were identified as belonging to Bifidobacterium species of predominantly human origin: B. adolescentis, B. bifidum, and B. catenulatum. Only one other species, Bifidobacterium choerinum, was detected with low frequency in a pork processing chain. B. pseudolongum subsp. pseudolongum was predominant in pig feces, whereas B. pseudolongum subsp. globosum was predominant in feces from other animal species. Four strains closely related to both subspecies (58 to 61% DNA reassociation) formed a distinct genomic group. PCR techniques, which are more rapid and sensitive than culture-based methods, could be used to detect directly B. pseudolongum and B. thermophilum as indicators of fecal contamination along the meat processing chain.