16S RIBOSOMAL-RNA GENE-SEQUENCES OF CANDIDATUS CAMPYLOBACTER-HOMINIS,A NOVEL UNCULTIVATED SPECIES, ARE FOUND IN THE GASTROINTESTINAL-TRACTOF HEALTHY HUMANS

Although some Campylobacter species are agents of gastroenteritis and periodontal disease in humans, little is known of the variety of campy lobacters in the gastrointestinal tract of healthy individuals. This p aper provides evidence for the existence of a previously undescribed, uncultivated Campylobacter species that may be a commensal in the heal thy human gut. Saliva and faeces from 20 healthy individuals were exam ined by PCR assays specific for nine species of campylobacter (C. sput orum, C. concisus, C. upsaliensis, C. helveticus, C lari, C. fetus, C. hyointestinalis, C. jejuni and C. cold and for the genus as a whole. Genus-specific amplicons were produced from 19 of 20 saliva samples an d from 18 of 20 faecal samples. C. concisus species-specific amplicons were produced from 19 of 20 saliva samples and 3 of 20 faecal samples . The faecal samples were all PCR-negative for other Campylobacter spe cies. Three unidentified 16S rRNA Campylobacter genus-specific amplico ns of faecal origin were sequenced. Phylogenetic analysis showed that these sequences were 99% similar, and clustered within the genus as a novel group which was termed HS (HS = healthy subject). A PCR primer p air specific for the HS group was designed from the sequence data and used to reexamine the original samples. Although it was not possible t o culture the organism from faeces, specific PCR assay detected it in 10 of the 20 faecal samples, but not in any corresponding saliva sampl es. The authors propose that the source of the amplicons is a previous ly undescribed and so far uncultivated species, which they term 'Candi datus Campylobacter hominis'.