Genetic diversity of vaginal lactobacilli isolated from women of different geographic areas

초록

Lactobacilli play an important role in maintaining vaginal health in women, but the taxonomy of these lactobacilli is confusing. The genus Lactobacillus contains more than 50 different species. Among them, more than 10 species are from human vaginal or intestinal sources. Little is known, however, about the genetic diversity within this group of bacteria. The aim of this study was to analyze the genetic diversity of vaginal lactobacilli. We selected 32 phenotypically different vaginal Lactobacillus strains isolated from women of seven different geographical areas. These included 8 strains from USA (2 were from Native Americans), 9 from Turkey, 5 from Brazil, 3 from China, 3 from Argentina, 2 from South Korea, and 2 from India. Then, chromosomal DNA of these strains were isolated, and the DNA fragments of their 16S rRNA genes were amplified by polymerase chain reaction with the universal 16S rRNA gene primers. The sequences were determined by ABI 377 automated DNA sequencer (Perkin Elmer). The sequence data of the 32 vaginal isolates and the existing data in GeneBank for 15 Lactobacillus reference strains were analyzed by the Clustal W program. A dendrogram was achieved by the neighbor-joining method of the PHYLIP package. The phylogenetic tree showed many distinct branches, indicating novel species. Among 32 clinical strains analyzed, only 2 were related to known species: L. paracasei and L. johnsonii. The remaining 30 strains apparently belonged to 25 novel species. In conclusion, vaginal lactobacilli may represent a large number of uncharacterized novel species, and further studies are needed to classify these species.