Dietary supplementation with probiotics during late pregnancy: outcome on vaginal microbiota and cytokine secretion

Abstract

Background: The vaginal microbiota of healthy women consists of a wide variety of anaerobic and aerobic bacterial genera and species dominated by the genus Lactobacillus. The activity of lactobacilli helps to maintain the natural healthy balance of the vaginal microbiota. This role is particularly important during pregnancy because vaginal dismicrobism is one of the most important mechanisms for preterm birth and perinatal complications. In the present study, we characterized the impact of a dietary supplementation with the probiotic VSL#3, a mixture of Lactobacillus, Bifidobacterium and Streptococcus strains, on the vaginal microbiota and immunological profiles of healthy women during late pregnancy.

Results: An association between the oral intake of the probiotic VSL#3 and changes in the composition of the vaginal microbiota of pregnant women was revealed by PCR-DGGE population profiling. Despite no significant changes were found in the amounts of the principal vaginal bacterial populations in women administered with VSL#3, qPCR results suggested a potential role of the probiotic product in counteracting the decrease of Bifidobacterium and the increase of Atopobium, that occurred in control women during late pregnancy. The modulation of the vaginal microbiota was associated with significant changes in some vaginal cytokines. In particular, the decrease of the anti-inflammatory cytokines IL-4 and IL-10 was observed only in control women but not in women supplemented with VSL#3. In addition, the probiotic consumption induced the decrease of the pro-inflammatory chemokine Eotaxin, suggesting a potential anti-inflammatory effect on the vaginal immunity.

Conclusion: Dietary supplementation with the probiotic VSL#3 during the last trimester of pregnancy was associated to a modulation of the vaginal microbiota and cytokine secretion, with potential implications in preventing preterm birth.

Trial registration: ClinicalTrials.gov NCT01367470.

Figure 1

PCR-DGGE analysis with universal primers for bacteria. Analysis was conducted on the vaginal samples collected at 33^rd (W33) and 37^th (W37) week of gestation from 15 women supplemented with the probiotic VSL#3 [(P) N. 1–15] and 12 control women [(C) N. 16–27]. N: woman number; W: week of gestation; T: type of supplementation. (A) PCR-DGGE fingerprints. M, external reference marker. (B) Dendrogram of the DGGE profiles shown in panel A. Pearson correlation was used to calculate the similarity in DGGE profiles.

Figure 2

PCR-DGGE analysis with Lactobacillus-specific primers. Analysis was conducted on the vaginal samples collected at 33^rd (W33) and 37^th (W37) week of gestation from 15 women supplemented with the probiotic VSL#3 [(P) N. 1–15] and 12 control women [(C) N. 16–27]. N: woman number; W: week of gestation; T: type of supplementation. (A) PCR-DGGE fingerprints. M, external reference marker. Band L16 corresponds to L. helveticus (GenBank accession number: AB571603) (B) Dendrogram of the DGGE profiles shown in panel A. Pearson correlation was used to calculate the similarity in DGGE profiles.

Figure 3

qPCR evaluation of Lactobacillus(A),Bifidobacterium(B),Atopobium(C)andPrevotella(D). Analysis was performed on vaginal samples collected at 33^rd (W33) and 37^th (W37) week of gestation from pregnant women supplemented (P) and not supplemented (C) with VSL#3. Data are expressed as ng of DNA of the target genus per μg of total bacterial DNA extracted from the vaginal sample. The diagrams show the mean values with error bars representing the standard deviations.

Figure 4

Cytokines and chemokines whose concentration significantly changed during the study period (P<0.05). P, probiotic group; C, control group; W33, 33^rd gestational week (black colour); W37, 37^th gestational week (grey colour). Cytokine or chemokine names are reported in x-axis. Data are expressed as pg of the target cytokine or chemokine per μg of total proteins present in the vaginal sample (y-axis). The diagrams show means with error bars representing the standard deviations.

Figure 5

Women registering significant variations in total levels of immune-mediators. P, probiotic group; C, control group; W33, 33^rd gestational week (black colour); W37, 37^th gestational week (grey colour). Identification numbers of women registering significant variations are reported in x-axis. Data are expressed as pg of total immune-mediators per μg of total vaginal proteins (y-axis). The diagrams show means with error bars representing the standard deviations.