Biology subjects

Kracht, D. J.

Publications and source records attributed to Kracht, D. J..

3 recordsLinked to original sources

bioRxiv2023

The vaginal microbiota of pregnant women varies with gestational age, maternal age, and parity

The composition of the vaginal microbiota is heavily influenced by pregnancy and may factor into pregnancy complications, including spontaneous preterm birth. However, results among studies have been inconsistent, due in part to variation in sample sizes and ethnicity. Thus an association between the vaginal microbiota and preterm labor continues to be debated. Yet, before assessing associations between the composition of the vaginal microbiota and preterm labor, a robust and in-depth characterization of the vaginal microbiota throughout pregnancy in the specific study population under investigation is required. Herein, we report a large longitudinal study (N = 474 women, 1862 vaginal samples) of a primarily African-American cohort- which experiences a relatively high rate of pregnancy complications - evaluating associations between individual identity, gestational age, and other maternal characteristics with the composition of the vaginal microbiota throughout gestation resulting in term delivery. The primary factors influencing the composition of the vaginal microbiota in pregnancy are individual identity and gestational age at sampling. Secondary factors are maternal age, parity, obesity, and self-reported Cannabis use. The principal pattern across gestation is for the vaginal microbiota to remain or transition to a state of Lactobacillus dominance. This pattern can be mitigated by maternal parity and obesity. Regardless, network analyses reveal dynamic associations among specific bacterial taxa within the vaginal ecosystem, which shift throughout the course of pregnancy. This study provides a robust foundational understanding of the vaginal microbiota in pregnancy among African-Americans, in particular, and sets the stage for further investigation of this microbiota in obstetrical disease. IMPORTANCEThere is debate regarding links between the vaginal microbiota and pregnancy complications, especially spontaneous preterm birth. Inconsistencies in results among studies are likely due to differences in sample sizes and cohort ethnicity. Ethnicity is a complicating factor because, although all bacterial taxa commonly inhabiting the vagina are present among all ethnicities, the frequencies of these taxa vary among ethnicities. Therefore, an in-depth characterization of the vaginal microbiota throughout pregnancy in the specific study population under investigation is required prior to evaluating associations between the vaginal microbiota and obstetrical disease. This initial investigation is a large longitudinal study of the vaginal microbiota throughout gestation resulting in a term delivery in a primarily African-American cohort, a population that experiences disproportionally negative maternal-fetal health outcomes. It establishes the magnitude of associations between maternal characteristics, such as age, parity, BMI, and self-reported Cannabis use, on the vaginal microbiota in pregnancy.

microbiology↗

bioRxiv2022

Microbiota of the pregnant mouse: characterization of the bacterial communities in the oral cavity, lung, intestine, and vagina through culture and DNA sequencing

Mice are frequently used as animal models for mechanistic studies of infection and obstetrical disease, yet characterization of the murine microbiota during pregnancy is lacking. The objective of this study was to therefore characterize the microbiotas of distinct body sites of the pregnant mouse that harbor microorganisms that could potentially invade the murine amniotic cavity leading to adverse pregnancy outcomes: vagina, oral cavity, intestine, and lung. The microbiotas of these body sites were characterized through anoxic, hypoxic, and oxic culture, as well as through 16S rRNA gene sequencing. With the exception of the vagina, the cultured microbiotas of each body site varied with atmosphere, with the greatest diversity in the cultured microbiota appearing under anoxic conditions. Only cultures of the vagina were able to recapitulate the microbiota observed from direct DNA sequencing of body site samples, primarily due to the dominance of two Rodentibacter strains. Identified as R. pneumotropicus and R. heylii, these isolates exhibited dominance patterns similar to those of Lactobacillus crispatus and L. iners in the human vagina. Whole genome sequencing of these Rodentibacter strains revealed shared genomic features, including the ability to degrade glycogen, an abundant polysaccharide in the vagina. In summary, we report body site specific microbiotas in the pregnant mouse with potential ecological parallels to those of humans. Importantly, our findings indicate that the vaginal microbiota of pregnant mice can be readily cultured, suggesting that mock vaginal microbiotas can be tractably generated and maintained for experimental manipulation in future mechanistic studies of host vaginal-microbiome interactions. IMPORTANCEMice are widely utilized as animal models of obstetrical complications; however, the characterization of the murine microbiota has been neglected during pregnancy. Microorganisms from the vagina, oral cavity, intestine, and lung have been found in the intra-amniotic space, where their presence threatens the progression of gestation. Herein, we characterize the microbiotas of pregnant mice and establish the appropriateness of culture in capturing the microbiota at each site. The high relative abundance of Rodentibacter observed in the vagina is similar to that of Lactobacillus in humans, suggesting potential ecological parallels. Importantly, we report that the vaginal microbiota of the pregnant mouse can be readily cultured under hypoxic conditions, demonstrating that mock microbial communities can be utilized to test the potential ecological parallels between microbiotas in human and murine pregnancy, and to evaluate the relevance of the structure of these microbiotas for adverse pregnancy outcomes, especially intra-amniotic infection and spontaneous preterm birth.

microbiology↗

bioRxiv2021

LACK OF EVIDENCE FOR A VIABLE MICROBIOTA IN MURINE AMNIOTIC FLUID

The existence of an amniotic fluid microbiota (i.e., a viable microbial community) in mammals is controversial. Its existence would require a fundamental reconsideration of the role of intra-amniotic microbes in fetal development and pregnancy outcomes. In this study, we determined whether the amniotic fluid of mice harbors a microbiota in late gestation. Bacterial profiles of amniotic fluids located proximally or distally to the cervix were characterized through quantitative real-time PCR, 16S rRNA gene sequencing, and culture (N = 21 mice). These profiles were compared to those of technical controls for background DNA contamination. The load of 16S rDNA in the amniotic fluid exceeded that in controls. Additionally, the 16S rDNA profiles of the amniotic fluid differed from those of controls, with Corynebacterium tuberculostearicum being differentially more abundant in amniotic fluid profiles; however, this bacterium was not cultured. Of the 42 total bacterial cultures of amniotic fluids, only one yielded bacterial growth - Lactobacillus murinus. The 16S rRNA gene of this common murine-associated bacterium was not detected in any amniotic fluid sample, suggesting it did not originate from the amniotic fluid. No differences in 16S rDNA load, 16S rDNA profile, or bacterial culture were observed between amniotic fluids located proximal and distal to the cervix. Collectively, these data show that, although there is a modest DNA signal of bacteria in murine amniotic fluid, there is no evidence that this signal represents a viable microbiota. These findings refute the proposed role of amniotic fluid as a source of microorganisms for in utero colonization. IMPORTANCEThe prevailing paradigm in obstetrics has been the sterile womb hypothesis, which posits that fetuses are first colonized by microorganisms during labor and/or the vaginal delivery process. However, it has been suggested that fetuses are consistently colonized in utero. One proposed source of colonizers is the amniotic fluid surrounding the fetus. This concept has been derived primarily from investigations that relied on DNA sequencing. Due to the low microbial biomass of amniotic fluid, such studies are susceptible to influences of background DNA contamination. Additionally, even if there is a microbial DNA signature in amniotic fluid, this is not necessarily reflective of a resident microbiota that could colonize the mammalian fetus. In the current study, using multiple microbiologic approaches and incorporating technical controls for DNA contamination, we show that, although there is a low abundance bacterial DNA signal in amniotic fluid, this does not translate to the presence of viable bacteria.

microbiology↗