Lactobacillus vaginalis

The species was identified by Embley and his coworkers in the course of a vaccine development against trichomoniasis.[1] The vaginal secretions of women suffering from trichomoniasis were examined for the presence of certain proposed Lactobacillus strains exhibiting mutualistic behavior with Trichomonas vaginalis, facilitating sustainment of infection.[1] The isolates initially designated L. fermentum were compared to the reference strains of a number of heterofermentative species using the DNA–DNA hybridization method, and have shown a maximal DNA homology of 35% with L. reuteri, far below the standard threshold of 70% recommended for species delineation.[1] The new species L. vaginalis with type strain NCTC 12197 was proposed, and the description of its carbohydrate fermentation patterns as well as cellular fatty acid composition were provided.[1] Further taxonomic investigations relying on 16S rRNA gene sequence analysis placed L. vaginalis in the L. reuteri phylogenetic group along with 14 other species, including L. fermentum.[2]

L. vaginalis is a Gram-positive, facultatively anaerobic, catalase negative bacterium.[1] These obligate heterofermentative lactobacilli produce both D and L isomers of lactic acid as the metabolic end-product of carbohydrate fermentation.[1] Similarly to most other vaginal Lactobacillus species, L. vaginalis does not directly metabolize glycogen, but rather its depolymerization products.[3] The bacterium occurs in less than 1% of healthy women.[4]

Specific strains of L. vaginalis characterized by an insufficient protective efficacy against vaginal pathogens are used in lactobacillus vaccines, a therapy method of chronic vaginal infections that respond poorly to antibiotic treatment, available in German-speaking Europe.[5] L. vaginalis is not used as a probiotic, nor as a starter culture in the food industry. It is occasionally isolated from fermented dairy products, where it represents an unwanted contaminant.[6]