Abstract
Asymptomatic bacterial vaginosis (BV) in reproductive-age women has serious obstetric and gynecological consequences. Despite its high incidence, the behavior of vaginal lactobacilli in asymptomatic BV is unknown. We analyzed the functional properties of previously isolated vaginal lactobacilli from asymptomatic women with normal, intermediate, and BV microbiota. Lactic acid and antimicrobial activity against seven urogenital pathogens were evaluated from lactobacilli cell-free culture supernatants (CFCs) (n = 207) after 48 h incubation in MRS. Lactobacilli isolates were used to evaluate H2O2, autoaggregation and coaggregation with C. albicans. Lactobacilli from normal microbiota produced more d-lactate than lactobacilli from intermediate and asymptomatic BV (p = 0.007). L. plantarum, L. fermentum and L. reuteri produced greater d-lactate whereas L. rhamnosus, L. crispatus, L. johnsonii were greater producers of l-lactate. Interspecies positive correlation was observed in the lactic acid contents of CFCs. Distribution of H2O2-producing lactobacilli did not vary significantly among the groups. When lactic acid isomers were considered, species from intermediate and BV microbiota clustered together with each other and distinctly from species of normal microbiota. Broad-spectrum antagonism (≥90% inhibition) against E. coli, C. albicans, S. aureus, P. aeruginosa, G. vaginalis, N. gonorrhoeae, S. agalactiae were displayed by 46.86% (97) of isolates. Our study highlights the differential functional properties of vaginal lactobacilli from women with normal microbiota and asymptomatic BV.
Highlights
Vaginal microbiota are one of the critical features in maintaining vaginal homeostasis and providing protection against urogenital infections
Of the 207 lactobacilli, 169 were recovered from normal microbiota, 15 from intermediate, and 23 from asymptomatic bacterial vaginosis (BV). These 207 lactobacilli comprised of 12 different Lactobacillus species that constitutes L. reuteri (42, 20.29%), L. rhamnosus (40, 19.32%), L. gasseri (22, 10.62%), L. jensenii (18, 8.69%), L. crispatus (14, 6.76%) and L. salivarius (14, 6.76%)
These observations are in contrast to previous reports on lactic acid from eubiotic and dysbiotic microbiota [12,28]. This discrepancy could be due to the detection of lactic acid from cervicovaginal fluid samples in the earlier reports and the use of axenic cultures in the present study. This implies that during asymptomatic BV, which is characterized by reduction in Lactobacillus abundance and diversity, the remaining lactobacilli strains are capable of producing lactic acid when suitable environmental conditions are provided. d-lactic acid, which is an isomer of l-lactic acid, has a greater protective role than l- lactic acid [13]
Summary
Vaginal microbiota are one of the critical features in maintaining vaginal homeostasis and providing protection against urogenital infections. Bacterial vaginosis is the most common reproductive tract infection in women which could be symptomatic (with symptoms) or asymptomatic (without manifestation of clinical symptoms) [4]). Apart from symptomatic cases, incidences of asymptomatic BV can be 14.5% to as high as 84% [4,5,6]. Both symptomatic and asymptomatic BV has been associated with severe obstetrics’ and gynecological consequences [7,8,9,10]. Despite the increased risk of other infections, reproductive morbidity, and complications, asymptomatic BV is understudied
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