Lactobacillus species: colonization after treatment for bacterial vaginosis (BV) and their inhibitory potential to (BV) associated bacteria

Abstract

Maintenance of a normal vaginal flora is important in the prevention of sexually transmitted infections including gonorrhoea and Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS). Lactobacillus species predominate a healthy vaginal flora and produce chemicals that are toxic to pathogenic microorganisms. Reduction in the number of Lactobacilli in the vagina may result in bacterial vaginosis (BV) characterized by adverse pregnancy outcomes including preterm birth, premature rupture of uterine membranes and amnionitis. BV has also been associated with increased risk of acquisition of HIV and although this condition can be easily treated with antibiotics, recurrence after treatment is common. The reasons for the recurrence have been linked to hygiene practices such as vaginal douching, multiple sexual partners, and other sexually transmitted infections (STIs). Evidence also suggests that failure to establish normal flora following antimicrobial therapy contributes to the recurrence. The main objective of the study was characterise Lactobacillus species isolated from vaginal tracts of women following BV treatment and to document their inhibitory capacity against G. vaginalis, B. fragilis spp, P. bivia and Mobiluncus spp. Lactobacillus spp were isolated from women treated for BV two months earlier to determine the diversity of the Lactobacillus species recolonising the vagina post treatment. Lactobacilli were also tested for hydrogen peroxide (H202) production and their inhibitory potential to pathogens associated with BV. The organisms were identified by morphologically and by biochemicals. H202 production was determined using tetramethylbenzidine agar and inhibitory activity by a deferred antagonism well assay in which Lactobacilli suspension was inoculated into wells cut in agar to which Gadnerella vaginalis, Bacteroides fragilis, Prevotella bivia and Mobiluncus spp suspension was seeded. The prevalence of BV among the women tested was 38.3%. A wide diversity of Lactobacilli was identified with with L. jensenii being the most predominant Lactobacilli (18.4%). Thirty seven percent of the women were colonized by H202 producing Lactobacilli, and of these the majority of those with the H202 positive Lactobacilli had BV associated micro flora. When inhibitory potential of the Lactobacilli was tested, 23% were inhibitory to G. vaginalis, P. bivia and Mobiluncus spp. None of the Lactobacilli tested inhibited B. fragilis. Only about a third (37%) of the women were colonized with H202 positive Lactobacilli (LB). It was also observed that H202 positive LB were more inhibitory to indicator bacteria and therefore important in preventing growth of pathogens. Therefore, in a large proportion of women, H202 positive LB failed to recolonize following treatment and as a result remain unprotected from colonization with pathogens. In conclusion, the results f this study found that in spite of the Lactobacillus strains being capable of producing H202, acid and bacteriocins, not all strains producing each of these substances were inhibitory; for example, despite some strains producing H202 they were not inhibitory, some produced highly acidic culture supernatants yet they would not inhibit the indicator bacteria. Therefore we would suggest that there could be a synergistic action of these substances to make the overall effect. Based on the results of this study, it would be recommended that in management of BV, conventional treatment using antibiotics like metronindazole should be augmented by biotherapy using Lactobacilli producing inhibitory compounds to re-establish a normal vaginal microflora.