Interstrain Variability of Human Vaginal Lactobacillus crispatus for Metabolism of Biogenic Amines and Antimicrobial Activity against Urogenital Pathogens.

Lactobacillus crispatus is the dominant species in the vagina of many women. With the potential for strains of this species to be used as a probiotic to help prevent and treat dysbiosis, we investigated isolates from vaginal swabs with Lactobacillus-dominated and a dysbiotic microbiota. A comparative genome analysis led to the identification of metabolic pathways for synthesis and degradation of three major biogenic amines in most strains. However, targeted metabolomic analysis of the production and degradation of biogenic amines showed that certain strains have either the ability to produce or to degrade these compounds. Notably, six strains produced cadaverine, one produced putrescine, and two produced tyramine. These biogenic amines are known to raise vaginal pH, cause malodour, and make the environment more favourable to vaginal pathogens. In vitro experiments confirmed that strains isolated from women with a dysbiotic vaginal microbiota have higher antimicrobial effects against the common urogenital pathogens Escherichia coli and Enterococcus faecium. The results indicate that not all L. crispatus vaginal strains appear suitable for probiotic application and the basis for selection should not be only the overall composition of the vaginal microbiota of the host from which they came, but specific biochemical and genetic traits.

Metabolomics as a clinical testing method for the diagnosis of vaginal dysbiosis.

Microbes play an important role in vaginal health, with lactobacilli a particularly abundant species. When dysbiosis occurs, the tools to determine whether it is a condition such as bacterial vaginosis, and whether it warrants antibiotic treatment, are currently suboptimal. We propose that standardization and implementation of an affordable metabolomics-based diagnostic technique could reduce instances of false positives, stress associated with misdiagnosis, and potentially save time and money. Basing diagnosis on the detection of pH elevated above 4.5 and specific polyamines could provide a better method to assist a physician determine whether treatment is warranted.