Abstract
BackgroundDespite their antimicrobial potential, vaginal lactobacilli often fail to retain dominance, resulting in overgrowth of the vagina by other bacteria, as observed with bacterial vaginosis. It remains elusive however to what extent interindividual differences in vaginal Lactobacillus community composition determine the stability of this microflora. In a prospective cohort of pregnant women we studied the stability of the normal vaginal microflora (assessed on Gram stain) as a function of the presence of the vaginal Lactobacillus index species (determined through culture and molecular analysis with tRFLP).ResultsFrom 100 consecutive Caucasian women vaginal swabs were obtained at mean gestational ages of 8.6 (SD 1.4), 21.2 (SD 1.3), and 32.4 (SD 1.7) weeks, respectively. Based on Gram stain, 77 women had normal or Lactobacillus-dominated vaginal microflora (VMF) during the first trimester, of which 18 had grade Ia (L. crispatus cell morphotypes) VMF (23.4%), 16 grade Iab (L. crispatus and other Lactobacillus cell morphotypes) VMF (20.8%), and 43 grade Ib (non-L. crispatus cell morphotypes) VMF (55.8%). Thirteen women with normal VMF at baseline, converted in the second or third trimester (16.9%) to abnormal VMF defined as VMF dominated by non-Lactobacillus bacteria. Compared to grade Ia and grade Iab VMF, grade Ib VMF were 10 times (RR = 9.49, 95% CI 1.30 – 69.40) more likely to convert from normal to abnormal VMF (p = 0.009). This was explained by the observation that normal VMF comprising L. gasseri/iners incurred a ten-fold increased risk of conversion to abnormal VMF relative to non-L. gasseri/iners VMF (RR 10.41, 95% CI 1.39–78.12, p = 0.008), whereas normal VMF comprising L. crispatus had a five-fold decreased risk of conversion to abnormal VMF relative to non-L. crispatus VMF (RR 0.20, 95% CI 0.05–0.89, p = 0.04).ConclusionThe presence of different Lactobacillus species with the normal vaginal microflora is a major determinant to the stability of this microflora in pregnancy: L. crispatus promotes the stability of the normal vaginal microflora while L. gasseri and/or L. iners predispose to some extent to the occurrence of abnormal vaginal microflora.
Highlights
Despite their antimicrobial potential, vaginal lactobacilli often fail to retain dominance, resulting in overgrowth of the vagina by other bacteria, as observed with bacterial vaginosis
Vaginal microflora status according to Gram stain at baseline and on follow-up Based on Gram stain, 77 women presented with normal or grade I vaginal microflora (VMF) during the first trimester, of which 18 had grade Ia VMF (23.4%), 16 grade Iab (L. crispatus and other Lactobacillus cell morphotypes) VMF (20.8%), and 43 grade Ib VMF (55.8%)
It was recently established that of the 80 known Lactobacillus species, up to 20 different species may colonize the intestinal tract, yet merely four species seem to dominate the vaginal microflora, in particular L. crispatus, L. jensenii, L. gasseri and L. iners [7,17,18], a finding that has been corroborated in various parts of the world among women with differing ethnicity[20], albeit a fifth species L. vaginalis may have been overlooked by culture-independent methods
Summary
Vaginal lactobacilli often fail to retain dominance, resulting in overgrowth of the vagina by other bacteria, as observed with bacterial vaginosis. The lactobacillidriven defence of the vaginal niche is in its essence seized as a principle of colonisation resistance, i.e. the vaginal lactobacilli prevent colonisation of the vaginal epithelium by other microorganisms, through a variety of mechanisms [3] Despite their intrinsic antimicrobial potential vaginal lactobacilli fail to retain dominance in a considerable number of women, resulting in overgrowth of the vaginal epithelium by other bacteria, as observed, most typically, with anaerobic polymicrobial overgrowth in bacterial vaginosis [1], or less commonly, with overgrowth by streptococci, including group A [4] and group B streptococci [5,6], by bifidobacteria [7,8], or by coliforms such as E. coli [5,6,9]. The ecological conditions of the vaginal niche, like the low pH, which enable lactobacilli to inhibit overgrowth by other microorganisms, are intermittently disturbed by non-microbial factors, primarily by the menses [14] and by sexual intercourse [15], to which some practices like vaginal douching [16] may add further disturbance
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
