Human Milk Oligosaccharides Reduce Murine Group B Streptococcus Vaginal Colonization with Minimal Impact on the Vaginal Microbiota

During pregnancy, GBS ascension into the uterus can cause fetal infection or preterm birth. In addition, GBS exposure during labor creates a risk of serious disease in the vulnerable newborn and mother postpartum.

Efficacy of an experimental gonococcal lipooligosaccharide mimitope vaccine requires terminal complement

A safe and effective vaccine against multidrug-resistant gonorrhea is urgently needed. An experimental peptide vaccine called TMCP2 that mimics an oligosaccharide epitope in gonococcal lipooligosaccharide, when adjuvanted with glucopyranosyl lipid adjuvant-stable emulsion (GLA-SE), elicits bactericidal IgG and hastens clearance of gonococci in the mouse vaginal colonization model. Here, we show that efficacy of TMCP2 requires an intact terminal complement pathway, evidenced by loss of activity in C9 -/- mice or when C7 function was blocked. In conclusion, TMCP2 vaccine efficacy in the mouse vagina requires membrane attack complex. Serum bactericidal activity may serve as a correlate of protection for TMCP2.

Group B Streptococcus CAMP Factor Does Not Contribute to Interactions with the Vaginal Epithelium and Is Dispensable for Vaginal Colonization in Mice

Group B Streptococcus (GBS) remains a pervasive pathogen for pregnant women and their newborns. Maternal screening and intrapartum antibiotic prophylaxis to GBS-positive mothers have reduced, but not eliminated GBS neonatal disease, and have not impacted GBS-associated preterm birth or stillbirth.

Human milk oligosaccharides reduce murine group B Streptococcus vaginal colonization with minimal impact on the vaginal microbiota

Group B Streptococcus (GBS) colonizes the vaginal mucosa of a significant percentage of healthy women and is a leading cause of neonatal bacterial infections. Currently, pregnant women are screened in the last month of pregnancy and GBS-positive women are given antibiotics during parturition to prevent bacterial transmission to the neonate. Recently, human milk oligosaccharides (HMOs) isolated from breastmilk were found to inhibit GBS growth and biofilm formation in vitro, and women that make certain HMOs are less likely to be vaginally colonized with GBS. Using in vitro human vaginal epithelial cells and a murine vaginal colonization model, we tested the impact of HMO treatment on GBS burdens and the composition of the endogenous microbiota by 16S rRNA amplicon sequencing. HMO treatment reduced GBS vaginal burdens in vivo with minimal alterations to the vaginal microbiota. HMOs displayed potent inhibitory activity against GBS in vitro, but HMO pretreatment did not alter adherence of GBS or the probiotic Lactobacillus rhamnosus to human vaginal epithelial cells. Additionally, disruption of a putative GBS glycosyltransferase (Δsan_0913) rendered the bacterium largely resistant to HMO inhibition in vitro and in vivo but did not compromise its adherence, colonization, or biofilm formation in the absence of HMOs. We conclude that HMOs are a promising therapeutic bioactive to limit GBS vaginal colonization with minimal impacts on the vaginal microenvironment.

Bacterial and Host Determinants of Group B Streptococcal Vaginal Colonization and Ascending Infection in Pregnancy

Group B streptococcus (GBS) is a gram-positive bacteria that asymptomatically colonizes the vaginal tract. However, during pregnancy maternal GBS colonization greatly predisposes the mother and baby to a wide range of adverse outcomes, including preterm birth (PTB), stillbirth, and neonatal infection. Although many mechanisms involved in GBS pathogenesis are partially elucidated, there is currently no approved GBS vaccine. The development of a safe and effective vaccine that can be administered during or prior to pregnancy remains a principal objective in the field, because current antibiotic-based therapeutic strategies do not eliminate all cases of invasive GBS infections. Herein, we review our understanding of GBS disease pathogenesis at the maternal-fetal interface with a focus on the bacterial virulence factors and host defenses that modulate the outcome of infection. We follow GBS along its path from an asymptomatic colonizer of the vagina to an invasive pathogen at the maternal-fetal interface, noting factors critical for vaginal colonization, ascending infection, and vertical transmission to the fetus. Finally, at each stage of infection we emphasize important host-pathogen interactions, which, if targeted therapeutically, may help to reduce the global burden of GBS.

Role of dipA and pilD in Francisella tularensis Susceptibility to Resazurin

The phenoxazine dye resazurin exhibits bactericidal activity against the Gram-negative pathogens Francisella tularensis and Neisseria gonorrhoeae. One resazurin derivative, resorufin pentyl ether, significantly reduces vaginal colonization by Neisseria gonorrhoeae in a mouse model of infection. The narrow spectrum of bacteria susceptible to resazurin and its derivatives suggests these compounds have a novel mode of action. To identify potential targets of resazurin and mechanisms of resistance, we isolated mutants of F. tularensis subsp. holarctica live vaccine strain (LVS) exhibiting reduced susceptibility to resazurin and performed whole genome sequencing. The genes pilD (FTL_0959) and dipA (FTL_1306) were mutated in half of the 46 resazurin-resistant (RZR) strains sequenced. Complementation of select RZR LVS isolates with wild-type dipA or pilD partially restored sensitivity to resazurin. To further characterize the role of dipA and pilD in resazurin susceptibility, a dipA deletion mutant, ΔdipA, and pilD disruption mutant, FTL_0959d, were generated. Both mutants were less sensitive to killing by resazurin compared to wild-type LVS with phenotypes similar to the spontaneous resazurin-resistant mutants. This study identified a novel role for two genes dipA and pilD in F. tularensis susceptibility to resazurin.

Evaluation of SARS-CoV-2 in the Vaginal Secretions of Women with COVID-19: A Prospective Study

Objective: We aimed to investigate the likelihood of vaginal colonization with Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in pregnant and non-pregnant women with Coronavrus Disease 2019 (COVID-19). Materials and Methods: Vaginal swabs were taken from women diagnosed with mild to moderately acute SARS-CoV-2 infection, at Wolfson Medical Center, Israel, from March 2020 through October 2020. COVID-19 was diagnosed by real-time polymerase chain reaction (RT-PCR) performed on nasopharyngeal swabs. Vaginal swabs were tested for the presence of SARS-CoV-2 by reverse transcription polymerase chain reaction (RT-PCR). Results: In total, 51 women diagnosed with COVID-19 were included in the study. Of the 51 women with COVID-19 enrolled in this study, 16 (31.4%) were pregnant at enrollment and 35 (68.6%) were non-pregnant. Mean age was 43.5 ± 15.3 years (range 21–74 years). Compared to the non-pregnant group, the pregnant group was characterized by a higher white blood cell and absolute neutrophil count (p = 0.02 and p = 0.027, respectively). The non-pregnant patients were more likely to have chronic diseases (p = 0.035) and to be hospitalized (p < 0.001). Only one patient (1.9%) aged 60 years tested positive for SARS-CoV-2 in vaginal secretions. Mean gestational age at the diagnosis of COVID-19 of the pregnant group was 32.3 ± 7.8 weeks. Thirteen patients delivered during the study period; all delivered at term without obstetric complications and all neonates were healthy. Conclusions: Detection of SARS-CoV-2 in the vaginal secretions of patients diagnosed with COVID-19 is rare. Vaginal colonization may occur during the viremia phase of the disease, although infectivity from vaginal colonization needs to be proven.