Characterisation and selection of a Lactobacillus species to re-colonise the vagina of women with recurrent bacterial vaginosis

This paper reports the results of characterising and selecting a strain of Lactobacillus for potential use as a probiotic in regenerating the vaginal flora of women with recurrent episodes of bacterial vaginosis (BV). BV is a condition characterised by a depletion of vaginal lactobacilli accompanied by an overgrowth of a mixed vaginal flora of aerobic, anaerobic and micro-aerophilic species in very large numbers. BV has been associated with various gynaecological and obstetric complications and has an extremely high recurrence rate, due in part to the failure to establish a normal vaginal flora after antimicrobial therapy. A total of 60 vaginal isolates of lactobacilli was assessed for characteristics considered important for vaginal re-colonisation. The characteristics studied were the in-vitro inhibitory activity of the lactobacilli against bacterial species isolated from women with recurrent BV, acid production after growth of the lactobacilli in liquid culture, production of hydrogen peroxide (H2O2) and adhesiveness of the lactobacilli to exfoliated vaginal epithelial cells (VEC). Four strains of lactobacilli, L. acidophilus (61701 and 61880), L. crispatus (55730) and L. delbrueckii subsp. delbrueckii (65407), demonstrated the greatest inhibitory activity against the BV-associated bacterial species. Two of these isolates (55730 and 61880) produced H2O2. All four isolates produced a highly acidic environment after growth in liquid medium (pH <4). Only one of these (strain 61701) was strongly adherent to VEC (>100 bacteria/VEC). A further isolate (L. acidophilus 48101) did not demonstrate maximum inhibitory activity against BV-associated bacteria, but was found to be a strong producer of H2O2 and was also highly adherent to VEC. Isolates 61701 and 48101 could be candidates for use as probiotics for vaginal re-colonisation.