Abstract
Bacterial vaginosis (BV) causes genital inflammation and increased HIV acquisition risk. The standard-of-care for BV, antibiotic therapy, is associated with high recurrence rates. Probiotics may improve treatment outcomes, although substantial heterogeneity in efficacy has been observed during clinical trials. To evaluate the potential to improve existing probiotics, we compared the inflammatory and antimicrobial (adhesion, H2O2, D-lactate and L-lactate production) characteristics of 23 vaginal Lactobacillus isolates from South African women, commercial vaginal probiotics (L. casei rhamnosus, L. acidophilus) and 4 reference strains. All lactobacilli induced inflammatory cytokine production by genital epithelial cells and produced D-lactate. Of six isolates assessed, five suppressed inflammatory responses to Gardnerella vaginalis. Although the L. acidophilus probiotic was the most adherent, many clinical isolates produced greater amounts of H2O2, D-lactate and L-lactate than the probiotics. The most L-lactate and H2O2 were produced by L. jensenii (adjusted p = 0.0091) and L. mucosae (adjusted p = 0.0308) species, respectively. According to the characteristics evaluated, the top 10 isolates included 4 L. jensenii, 2 L. crispatus, 1 L. mucosae, 1 L. vaginalis and the L. acidophilus probiotic. There is potential to develop an improved vaginal probiotic using clinical Lactobacillus isolates. Inflammatory profiles are critical to evaluate as some isolates induced substantial cytokine production.
Highlights
Bacterial vaginosis (BV) is a highly prevalent dysbiosis of the vaginal microbiota that is characterized by a shift from predominantly Lactobacillus species to a diverse population including pathogenic bacteria, such as Gardnerella vaginalis and Prevotella spp[1]
Two commercial vaginal probiotics were found on the South African market and lactobacilli isolated from these probiotics were evaluated
Adjunctive probiotic treatment for BV may promote vaginal recolonization with healthy lactobacilli, BV treatment outcomes have been heterogeneous in probiotic clinical trials
Summary
Bacterial vaginosis (BV) is a highly prevalent dysbiosis of the vaginal microbiota that is characterized by a shift from predominantly Lactobacillus species to a diverse population including pathogenic bacteria, such as Gardnerella vaginalis and Prevotella spp[1]. The role of H2O2 in protection against BV-associated bacteria is controversial, as some studies have reported that physiological concentrations are not microbicidal and that, at microbicidal concentrations, H2O2 inhibits lactobacilli more effectively than pathogenic bacteria[19]. Competitive exclusion is another important protective mechanism utilized by lactobacilli, whereby adherent lactobacilli prevent the adhesion of pathogens to the vaginal epithelium and colonization[20]. Suppression of inflammatory responses by lactobacilli and lactic acid is another proposed mechanism for reduced susceptibility to HIV in women with Lactobacillus-dominant microbiota[22]. The aims of this study were to compare the antimicrobial and inflammatory characteristics of existing vaginal probiotics on the South African market to those of clinical Lactobacillus isolates from the FGTs of South African women
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