Three 16S rRNA hybridization probes were developed and tested for genus-specific detection of Bifidobacterium species in the human fecal flora. Variable regions V2, V4, and V8 of the 16S rRNA contained sequences unique to this genus and proved applicable as target sites for oligodeoxynucleotide probes. Determination of the genus specificity of the oligonucleotides was performed by whole-cell hybridization with fluorescein isothiocyanate-labelled probes. To this end, cells were fixed on glass slides, hybridized with the probes, and monitored by videomicroscopy. In combination with image analysis, this allowed quantification of the fluorescence per cell and objective evaluation of hybridization experiments. One of the probes developed was used to determine the population of Bifidobacterium spp. in human fecal samples. A comparison was made with results obtained by cultural methods for enumeration. Since both methods gave similar population estimates, it was concluded that all bifidobacteria in feces were culturable. However, since the total culturable counts were only a fraction of the total microscopic counts, the contribution of bifidobacteria to the total intestinal microflora was overestimated by almost 10-fold when cultural methods were used as the sole method for enumeration.

No abstract

Periodontal sulfate-reducing bacteria are associated with several clinical categories of periodontitis and with periodontal sites of increased pocket depth.

The aim of this study was to monitor the presence of sulfate-reducing bacteria (SRB) at different sites in the mouths of both healthy individuals and periodontitis patients. In 20 healthy subjects and 21 periodontitis patients, samples were taken from the palate, vestibulum, dorsum of the tongue, supragingival plaque, and periodontal pockets. In order to demonstrate growth of SRB, samples were incubated in an anoxic chamber in a reduced growth-medium for SRB, with an iron-indicator for sulfide production. The SRB were detected throughout the oral cavity. They were found on the mucosa in 10% of both healthy subjects and periodontitis patients. On the tongue and in supragingival plaque, the frequency of detection was slightly higher (22% of the subjects). In contrast, 86% of the periodontitis patients harbored SRB in one or more pockets. In 1/3 of the patients, SRB were present in all 3 pockets that were sampled. The data indicated that SRB belong to the normal oral microbiota, and have a preference for periodontal pockets.