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Exposure to environmental contaminants can result in profound effects on the host immune system. One class of environmental toxicants, known as dioxins, are persistent environmental contaminants termed "forever chemicals". The archetype toxicant from this group of chemicals is 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD), an immunotoxicant that activates the aryl-hydrocarbon receptor pathway leading to a variety of changes in immune cell responses. Immune cell functions are crucial to the development and maintenance of healthy reproduction. Immune cells facilitate tolerance between at the maternal-fetal interface between the parent and the semi-allogenic fetus and help defend the gravid reproductive tract from infectious assault. Epidemiological studies reveal that exposure to environmental contaminants (such as TCDD) are linked to adverse reproductive health outcomes including endometriosis, placental inflammation, and preterm birth. However, little is known about the molecular mechanisms that underpin how environmental toxicant exposures impact immune functions at the maternal-fetal interface or within the reproductive tract in general. This review presents the most recent published work that studies interactions between dioxin or TCDD exposure, the host immune system, and reproduction., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Stephens, Horner, Avila, Spicer, Chinni, Bernabe, Hinton, Damo, Eastman, McCallister, Osteen and Gaddy.)

When coordinating and adhering to a surface, microorganisms produce a biofilm matrix consisting of extracellular DNA, lipids, proteins, and polysaccharides that are intrinsic to the survival of bacterial communities. Indeed, bacteria produce a variety of structurally diverse polysaccharides that play integral roles in the emergence and maintenance of biofilms by providing structural rigidity, adhesion, and protection from environmental stressors. While the roles that polysaccharides play in biofilm dynamics have been described for several bacterial species, the difficulty in isolating homogeneous material has resulted in few structures being elucidated. Recently, Cegelski and co-workers discovered that uropathogenic Escherichia coli (UPEC) secrete a chemically modified cellulose called phosphoethanolamine cellulose (pEtN cellulose) that plays a vital role in biofilm assembly. However, limited chemical tools exist to further examine the functional role of this polysaccharide across bacterial species. To address this critical need, we hypothesized that we could design and synthesize an unnatural glycopolymer to mimic the structure of pEtN cellulose. Herein, we describe the synthesis and evaluation of a pEtN cellulose glycomimetic which was generated using ring-opening metathesis polymerization. Surprisingly, the synthetic polymers behave counter to native pEtN cellulose in that the synthetic polymers repress biofilm formation in E. coli laboratory strain 11775T and UPEC strain 700415 with longer glycopolymers displaying greater repression. To evaluate the mechanism of action, changes in biofilm and cell morphology were visualized using high resolution field-emission gun scanning electron microscopy which further revealed changes in cell surface appendages. Our results suggest synthetic pEtN cellulose glycopolymers act as an antiadhesive and inhibit biofilm formation across E. coli strains, highlighting a potential new inroad to the development of bioinspired, biofilm-modulating materials.

Exposure to environmental toxicants (such as dioxins) has been epidemiologically linked to adverse reproductive health outcomes, including placental inflammation and preterm birth. However, the molecular underpinnings that govern these outcomes in gravid reproductive tissues remain largely unclear. Placental macrophages (also known as Hofbauer cells) are crucial innate immune cells that defend the gravid reproductive tract and help promote maternal-fetal tolerance. We hypothesized that exposure to environmental toxicants such as 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) could alter placental macrophage responses to inflammatory insults such as infection. To test this, placental macrophages were cultured in the presence or absence of TCDD and then infected with the perinatal pathogen Group B Streptococcus (GBS). Our results indicate that TCDD is lethal to placental macrophages at and above a 5 nM concentration and that sublethal dioxin exposure inhibits phagocytosis and cytokine production. Taken together, these results indicate that TCDD paralyzes placental macrophage responses to bacterial infection.

Preterm birth affects nearly 10% of all pregnancies in the United States, with 40% of those due, in part, to infections. Streptococcus agalactiae (Group B Streptococcus , GBS) is one of the most common perinatal pathogens responsible for these infections. Current therapeutic techniques aimed to ameliorate invasive GBS infections are less than desirable and can result in complications in both the neonate and the mother. To this end, the need for novel therapeutic options is urgent. Human milk oligosaccharides (HMOs), an integral component of human breast milk, have been previously shown to possess antiadhesive and antimicrobial properties. To interrogate these characteristics, we examined HMO-mediated outcomes in both in vivo and ex vivo models of GBS infection utilizing a murine model of ascending GBS infection, an EpiVaginal human organoid tissue model, and ex vivo human gestational membranes. Supplementation of HMOs resulted in diminished adverse pregnancy outcomes, decreased GBS adherence to gestational tissues, decreased colonization within the reproductive tract, and reduced proinflammatory immune responses to GBS infection. Taken together, these results highlight the potential of HMOs as promising therapeutic interventions in perinatal health., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Group B Streptococcus (GBS) is an encapsulated Gram-positive bacterial pathogen that causes severe perinatal infections. Human milk oligosaccharides (HMOs) are short-chain sugars that have recently been shown to possess antimicrobial and anti-biofilm activity against a variety of bacterial pathogens, including GBS. We have expanded these studies to demonstrate that HMOs can inhibit and dismantle biofilm in both invasive and colonizing strains of GBS. A cohort of 30 diverse strains of GBS were analyzed for susceptibility to HMO-dependent biofilm inhibition or destruction. HMOs were significantly effective at inhibiting biofilm in capsular-type- and sequence-type-specific fashion, with significant efficacy in CpsIb, CpsII, CpsIII, CpsV, and CpsVI strains as well as ST-1, ST-12, ST-19, and ST-23 strains. Interestingly, CpsIa as well as ST-7 and ST-17 were not susceptible to the anti-biofilm activity of HMOs, underscoring the strain-specific effects of these important antimicrobial molecules against the perinatal pathogen Streptococcus agalactiae., (© 2023 Wiley-VCH GmbH.)

Streptococcus agalactiae, also known as group B Streptococcus (GBS), is a Gram-positive encapsulated bacterium that colonizes the gastrointestinal tract of 30 to 50% of humans. GBS causes invasive infection during pregnancy that can lead to chorioamnionitis, funisitis, preterm prelabor rupture of membranes (PPROM), preterm birth, neonatal sepsis, and maternal and fetal demise. Upon infecting the host, GBS encounters sentinel innate immune cells, such as macrophages, within reproductive tissues. Once phagocytosed by macrophages, GBS upregulates the expression of the gene npx , which encodes an NADH peroxidase. GBS mutants with an npx deletion (Δ npx ) are exquisitely sensitive to reactive oxygen stress. Furthermore, we have shown that npx is required for GBS survival in both THP-1 and placental macrophages. In an in vivo murine model of ascending GBS vaginal infection during pregnancy, npx is required for invading reproductive tissues and is critical for inducing disease progression, including PPROM and preterm birth. Reproductive tissue cytokine production was also significantly diminished in Δ npx mutant-infected animals compared to that in animals infected with wild-type (WT) GBS. Complementation in trans reversed this phenotype, indicating that npx is critical for GBS survival and the initiation of proinflammatory signaling in the gravid host. IMPORTANCE This study sheds new light on the way that group B Streptococcus (GBS) defends itself against oxidative stress in the infected host. The enzyme encoded by the GBS gene npx is an NADH peroxidase that, our study reveals, provides defense against macrophage-derived reactive oxygen stress and facilitates infections of the uterus during pregnancy. This enzyme could represent a tractable target for future treatment strategies against invasive GBS infections.

Over the past century, human health has been enhanced by antimicrobial development. Following the deployment of the first antibiotics in the 1940s, bacterial resistance evolved and has increasingly outmaneuvered even the most promising antimicrobial agents. Accordingly, increased interest has been placed on alternative methods to circumvent antimicrobial resistance evolution. In the enclosed short review, we discuss the antimicrobial properties of human breast milk with a special emphasis on human milk oligosaccharides (HMOs). We recount studies across gram-negative and gram-positive pathogens, highlighting the usage of HMOs in promoting human health and wellness., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Adverse pregnancy outcomes affect 54 million people globally per year, with at least 50% of these attributed to infection during gestation. These include inflammation of the membranes surrounding the growing fetus (chorioamnionitis), preterm prelabor rupture of membranes (PPROM), preterm birth (PTB), early-onset disease (EOD) and late-onset disease (LOD), neonatal and maternal sepsis, and maternal or fetal demise. Although universal screening and implementation of intrapartum antibiotic prophylaxis (IAP) has improved EOD outcomes, these interventions have not reduced the incidences of LOD or complications occurring early on during pregnancy such as PPROM and PTB. Thus, novel therapies are needed to prevent adverse pregnancy outcomes and to ameliorate disease risk in vulnerable populations. Lactoferrin has recently been explored as a potential therapeutic as it demonstrates strong antimicrobial and anti-biofilm activity. Lactoferrin is a glycoprotein capable of iron chelation found in a variety of human tissues and is produced in high concentrations in human breast milk. In recent studies, lactoferrin has shown promise inhibiting growth and biofilm formation of streptococcal species, including Group B Streptococcus (GBS), a prominent perinatal pathogen. Understanding the interactions between lactoferrin and GBS could elucidate a novel treatment strategy for adverse pregnancy outcomes caused by GBS infection., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Perinatal infection with Streptococcus agalactiae, or Group B Streptococcus (GBS), is associated with preterm birth, neonatal sepsis, and stillbirth. Here, we study the interactions of GBS with macrophages, essential sentinel immune cells that defend the gravid reproductive tract. Transcriptional analyses of GBS-macrophage co-cultures reveal enhanced expression of a gene encoding a putative metal resistance determinant, cadD. Deletion of cadD reduces GBS survival in macrophages, metal efflux, and resistance to metal toxicity. In a mouse model of ascending infection during pregnancy, the ΔcadD strain displays attenuated bacterial burden, inflammation, and cytokine production in gestational tissues. Furthermore, depletion of host macrophages alters cytokine expression and decreases GBS invasion in a cadD-dependent fashion. Our results indicate that GBS cadD plays an important role in metal detoxification, which promotes immune evasion and bacterial proliferation in the pregnant host., (© 2022. The Author(s).)

Acinetobacter baumannii is a serious threat to human health, per the Centers for Disease Control and Prevention's latest threat assessment. A. baumannii is a Gram-negative opportunistic bacterial pathogen that causes severe community and nosocomial infections in immunocompromised patients. Treatment of these infections is confounded by the emergence of multi- and pan-drug resistant strains of A. baumannii . A. baumannii colonizes abiotic and biotic surfaces and evades antimicrobial challenges by forming biofilms, which are three-dimensional architectural structures of cells adhered to a substrate and encased in an extracellular matrix comprised of polymeric substances such as polysaccharides, proteins, and DNA. Biofilm-inhibiting compounds have recently gained attention as a chemotherapeutic strategy to prevent or disperse A. baumannii biofilms and restore the utility of traditional antimicrobial strategies. Recent work indicates that human milk oligosaccharides (HMOs) have potent antibacterial and biofilm-inhibiting properties. We sought to test the utility of HMOs against a bank of clinical isolates of A. baumannii to ascertain changes in bacterial growth or biofilm formation. Our results indicate that out of 18 strains tested, 14 were susceptible to the antibiofilm activities of HMOs, and that the potent antibiofilm activity was observed in strains isolated from diverse anatomical sites, disease manifestations, and across antibiotic-resistant and susceptible strains.

Group B Streptococcus (GBS) is one of the leading infection-related causes of adverse maternal and neonatal outcomes. This includes chorioamnionitis, which leads to preterm ruptures of membranes and can ultimately result in preterm or stillbirth. Infection can also lead to maternal and neonatal sepsis that may contribute to mortality. Currently, treatment for GBS infection include a bolus of intrapartum antibiotic prophylaxis to mothers testing positive for GBS colonization during late pregnancy. Lactoferrin is an antimicrobial peptide expressed in human breast milk, mucosal epithelia, and secondary granules of neutrophils. We previously demonstrated that lactoferrin possesses antimicrobial and antibiofilm properties against several strains of GBS. This is largely due to the ability of lactoferrin to bind and sequester iron. We expanded upon that study by assessing the effects of purified human breast milk lactoferrin against a panel of phenotypically and genetically diverse isolates of GBS. Of the 25 GBS isolates screened, lactoferrin reduced bacterial growth in 14 and biofilm formation in 21 strains. Stratifying the data, we observed that colonizing strains were more susceptible to the growth inhibition activity of lactoferrin than invasive isolates at lactoferrin concentrations between 250-750 µg/mL. Treatment with 750 µg/mL of lactoferrin resulted in differences in bacterial growth and biofilm formation between discrete sequence types. Differences in bacterial growth were also observed between capsular serotypes 1a and III. Maternally isolated strains were more susceptible to lactoferrin with respect to bacterial growth, but not biofilm formation, compared to neonatal sepsis isolates. Finally, high biofilm forming GBS strains were more impacted by lactoferrin across all isolates tested. Taken together, this study demonstrates that lactoferrin possesses antimicrobial and antibiofilm properties against a wide range of GBS isolates, with maternally isolated colonizing strains being the most susceptible., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lu, Guevara, Francis, Spicer, Moore, Chambers, Craft, Manning, Townsend and Gaddy.)

Group B Streptococcus (GBS) is an encapsulated Gram-positive pathogen that causes ascending infections of the reproductive tract during pregnancy. The capsule of this organism is a critical virulence factor that has been implicated in a variety of cellular processes to promote pathogenesis. Primarily comprised of carbohydrates, the GBS capsule and its synthesis is driven by the c apsule p olysaccharide s ynthesis ( cps ) operon. The cpsE gene within this operon encodes a putative glycosyltransferase that is responsible for the transfer of a Glc-1-P from UDP-Glc to an undecaprenyl lipid molecule. We hypothesized that the cpsE gene product is important for GBS virulence and ascending infection during pregnancy. Our work demonstrates that a GBS cpsE mutant secretes fewer carbohydrates, has a reduced capsule, and forms less biofilm than the wild-type parental strain. We show that, compared to the parental strain, the ΔcpsE deletion mutant is more readily taken up by human placental macrophages and has a significantly attenuated ability to invade and proliferate in the mouse reproductive tract. Taken together, these results demonstrate that the cpsE gene product is an important virulence factor that aids in GBS colonization and invasion of the gravid reproductive tract.

Acinetobacter baumannii is an opportunistic bacterial pathogen that causes severe infections in immunocompromised patients. The emergence of multi- and pan-drug resistant strains of A. baumannii from clinical sources has confounded treatment and enhanced morbidity and mortality associated with these infections. One way that A. baumannii circumnavigates environmental and antimicrobial challenge is by forming tertiary architectural structures of cells known as biofilms. Biofilm-inhibiting molecules could be deployed as a potential chemotherapeutic strategy to inhibit or disrupt A. baumannii biofilms and mitigate adverse outcomes due to infection. Lactoferrin is an innate immune glycoprotein produced in high concentrations in both human and bovine milk which has previously been shown to have antibacterial and antibiofilm activities. We sought to test lactoferrin against a bank of clinical isolates of A. baumannii to determine changes in bacterial growth or biofilm formation. Our results indicate that human lactoferrin has slightly more potent antibacterial activities than bovine lactoferrin against certain strains of A. baumannii and that these effects are associated with anatomical site of isolation. Additionally, we have shown that both bovine and human lactoferrin can inhibit A. baumannii biofilm formation and that these effects are associated with anatomical site of isolation and whether the strain forms robust or weak biofilms.

Urinary tract infections (UTIs) are caused by bacteria growing in complex, multicellular enclosed aggregates known as biofilms. Recently, a zwitterionic cellulose derivative produced in Escherichia coli (E. coli) was determined to play an important role in the formation and assembly of biofilms. In order to produce a minimal, yet structurally defined tool compound to probe the biology of the naturally occurring polymer, we have synthesized a zwitterionic phosphoethanolamine cellobiose (pEtN cellobiose) and evaluated its biofilm activity in the Gram-negative bacterium E. coli, a pathogen implicated in the pathogenesis of UTIs. The impact of synthetic pEtN cellobiose on biofilm formation was examined via colorimetric assays which revealed an increase in cellular adhesion to an abiotic substrate compared to untreated samples. Additionally, Congo red binding assays indicate that culturing E. coli in the presence of pEtN cellobiose enhances Congo Red binding to bacterial cells. These results reveal new opportunities to study the impact glycopolymers have on cellular adhesion in Gram-negative pathogens., (© 2021 Wiley-VCH GmbH.)

Cryptococcus neoformans is a fungal pathogen that causes cryptococcal meningitis in immunocompromised individuals. Existing antifungal treatment plans have high mammalian toxicity and increasing drug resistance, demonstrating the dire need for new, nontoxic therapeutics. Antimicrobial peptoids are one alternative to combat this issue. Our lab has recently identified a tripeptoid, AEC5, with promising efficacy and selectivity against C. neoformans. Here, we report studies into the broad-spectrum efficacy, killing kinetics, mechanism of action, in vivo half-life, and subchronic toxicity of this compound. Most notably, these studies have demonstrated that AEC5 rapidly reduces fungal burden, killing all viable fungi within 3 hours. Additionally, AEC5 has an in vivo half-life of 20+ hours and no observable in vivo toxicity following 28 days of daily injections. This research represents an important step in the characterization of AEC5 as a practical treatment option against C. neoformans infections., (© 2019 Wiley Periodicals, Inc.)