Analysis of fecal populations of bifidobacteria and lactobacilli and investigation of the immunological responses of their human hosts to the predominant strains

Abstract

The bifidobacterial and lactobacillus populations of fecal samples collected from 10 human subjects were studied. The numbers of bifidobacteria were similar in the fecal samples of all of the subjects, but lactobacillus numbers varied, even between samples collected from the same individual. Analysis of the composition of the bacterial populations by ribotyping and pulsed-field gel electrophoresis to differentiate between strains showed that, at least for the numerically predominant strains, each subject harbored a unique collection of bifidobacteria and lactobacilli. Predominant bifidobacterial and lactobacillus strains detected in the feces of each subject were used in immunological assays (lymphocyte transformation, serum antibody titers) to determine the influence of the bacteria on the immune system of their host. Immunoglobulin G antibodies reactive with lactobacilli were detected at high concentrations; antibodies reactive with bifidobacteria were present at lower concentrations. The antibodies appeared to be genus specific rather than strain specific. The results of the study emphasized the complexity of the relationship that exists between the intestinal microflora and the human host.

Genomic diversity of cultivable Lactobacillus populations residing in the neonatal and adult gastrointestinal tract

“…The numerically predominant species of bacteria are obligately anaerobic and are represented by both gram-positive and gram-negative genera (Tannock, 1994). It is estimated that more than 400 species of bacteria reside in the human gut, while only 30-40 species represent 99% of the microbiota found in any one human subject (Kimura et al, 1997). At birth, the newborn infant intestine is sterile, but is colonized rapidly thereafter by microorganisms from the mother and the surrounding environment.…”

“…In human faeces, lactobacilli generally account for less than 1% of the bacterial community and it has been reported that they were not detected in faecal samples collected from c. 27% of Americans (Finegold et al, 1983;Sghir et al, 2000). Particular Lactobacillus species are reported to be persistent in the intestinal tracts of some humans, undetectable in others or exhibiting temporal changes in strain composition (McCartney et al, 1996;Kimura et al, 1997). Lactobacillus acidophilus, Lactobacillus salivarius, Lactobacilli casei, Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus reuterii and Lactobacillus brevis are the most commonly isolated species from the human intestine (Mitsuoka, 1992).…”

Molecular approaches for identification and characterization of lactic acid bacteria

“…These facts, along with the size of the gene, make it a good evolutionary clock. 24 Though the 16S rRNA gene is a well-conserved universal marker, however, there are some shortcomings associated with its use. First, the 16S rRNA genes are so well conserved that it results in a limited resolving power.…”

“…Indeed, excellent subspecies differentiation has been shown using PFGE for a number of organisms, including lactobacilli and bifidobacteria. 24,33 In some cases PFGE has enabled the grouping of bacterial strains within a species, and there are various examples to assess the potential of this technique to characterize bacterial isolates as well. Further, the usefulness of PFGE has been adequately demonstrated in monitoring the changes in the predominant bifidobacterial and lactobacilli populations of human origin, both in individuals over time as well as between individuals.…”

“…Further, the usefulness of PFGE has been adequately demonstrated in monitoring the changes in the predominant bifidobacterial and lactobacilli populations of human origin, both in individuals over time as well as between individuals. 24 Strain typing has been successfully achieved by PFGE for the L. acidophilus complex, L. casei, L. delbrueckii and its three subspecies (bulgaricus, delbrueckii and lactis), L. fermentum, L.s helveticus, L.plantarum, L. rhamnosus and L.sakei. 34,35 Overall, PFGE has been shown to differentiate strains belonging to the same LAB species, to group strains within a species, to distinguish between strains of different LAB species, and even to place isolates in specific Lactobacillus species.…”