Person:

Onderdonk, Andrew

Background: The mechanisms for the association between birth by cesarean section and atopy and asthma are largely unknown. Objective: To examine whether cesarean section results in neonatal secretion of cytokines that are associated with increased risk of atopy and/or asthma in childhood. To examine whether the association between mode of delivery and neonatal immune responses is explained by exposure to the maternal gut flora (a marker of the vaginal flora). Methods: CBMCs were isolated from 37 neonates at delivery, and secretion of IL-13, IFN-γ, and IL-10 (at baseline and after stimulation with antigens [dust mite and cat dander allergens, phytohemagglutinin, and lipopolysaccharide]) was quantified by ELISA. Total and specific microbes were quantified in maternal stool. The relation between mode of delivery and cord blood cytokines was examined by linear regression. The relation between maternal stool microbes and cord blood cytokines was examined by Spearman's correlation coefficients. Results: Cesarean section was associated with increased levels of IL-13 and IFN-γ. In multivariate analyses, cesarean section was associated with an increment of 79.4 pg/ml in secretion of IL-13 by CBMCs after stimulation with dust mite allergen (P < 0.001). Among children born by vaginal delivery, gram-positive anaerobes and total anaerobes in maternal stool were positively correlated with levels of IL-10, and gram-negative aerobic bacteria in maternal stool were negatively correlated with levels of IL-13 and IFN-γ. Conclusion: Cesarean section is associated with increased levels of IL-13 and IFN-γ, perhaps because of lack of labor and/or reduced exposure to specific microbes (e.g., gram-positive anaerobes) at birth.

The human gut microbiota comprise a complex and dynamic ecosystem that profoundly affects host development and physiology. Standard approaches for analyzing time-series data of the microbiota involve computation of measures of ecological community diversity at each time-point, or measures of dissimilarity between pairs of time-points. Although these approaches, which treat data as static snapshots of microbial communities, can identify shifts in overall community structure, they fail to capture the dynamic properties of individual members of the microbiota and their contributions to the underlying time-varying behavior of host ecosystems. To address the limitations of current methods, we present a computational framework that uses continuous-time dynamical models coupled with Bayesian dimensionality adaptation methods to identify time-dependent signatures of individual microbial taxa within a host as well as across multiple hosts. We apply our framework to a publicly available dataset of 16S rRNA gene sequences from stool samples collected over ten months from multiple human subjects, each of whom received repeated courses of oral antibiotics. Using new diversity measures enabled by our framework, we discover groups of both phylogenetically close and distant bacterial taxa that exhibit consensus responses to antibiotic exposure across multiple human subjects. These consensus responses reveal a timeline for equilibration of sub-communities of micro-organisms with distinct physiologies, yielding insights into the successive changes that occur in microbial populations in the human gut after antibiotic treatments. Additionally, our framework leverages microbial signatures shared among human subjects to automatically design optimal experiments to interrogate dynamic properties of the microbiota in new studies. Overall, our approach provides a powerful, general-purpose framework for understanding the dynamic behaviors of complex microbial ecosystems, which we believe will prove instrumental for future studies in this field.

Background: The link between histologic acute chorioamnionitis and infection is well established in preterm deliveries, but less well-studied in term pregnancies, where infection is much less common. Methodology/Principal Findings We conducted a secondary analysis among 195 low-risk women with term pregnancies enrolled in a randomized trial. Histologic and microbiologic evaluation of placentas included anaerobic and aerobic cultures (including mycoplasma/ureaplasma species) as well as PCR. Infection was defined as ≥1,000 cfu of a single known pathogen or a ≥2 log difference in counts for a known pathogen versus other organisms in a mixed culture. Placental membranes were scored and categorized as: no chorioamnionitis, Grade 1 (subchorionitis and patchy acute chorioamnionitis), or Grade 2 (severe, confluent chorioamnionitis). Grade 1 or grade 2 histologic chorioamnionitis was present in 34% of placentas (67/195), but infection was present in only 4% (8/195). Histologic chorioamnionitis was strongly associated with intrapartum fever >38°C [69% (25/36) fever, 26% (42/159) afebrile, P<.0001]. Fever occurred in 18% (n = 36) of women. Most febrile women [92% (33/36)] had received epidural for pain relief, though the association with fever was present with and without epidural. The association remained significant in a logistic regression controlling for potential confounders (OR = 5.8, 95% CI = 2.2,15.0). Histologic chorioamnionitis was also associated with elevated serum levels of interleukin-8 (median = 1.3 pg/mL no histologic chorioamnionitis, 1.5 pg/mL Grade 1, 2.1 pg/mL Grade 2, P = 0.05) and interleukin-6 (median levels = 2.2 pg/mL no chorioamnionitis, 5.3 pg/mL Grade 1, 24.5 pg/mL Grade 2, P = 0.02) at admission for delivery as well as higher admission WBC counts (mean = 12,000cells/mm(^3) no chorioamnionitis, 13,400cells/mm(^3) Grade 1, 15,700cells/mm(^3) Grade 2, P = 0.0005). Conclusion/Significance: Our results suggest histologic chorioamnionitis at term most often results from a noninfectious inflammatory process. It was strongly associated with fever, most of which was related to epidural used for pain relief. A more ‘activated’ maternal immune system at admission was also associated with histologic chorioamnionitis.

Background: Menstrual Toxic Shock Syndrome (mTSS) is thought to be associated with the vaginal colonization with specific strains of Staphylococcus aureus TSST-1 in women who lack sufficient antibody titers to this toxin. There are no published studies that examine the seroconversion in women with various colonization patterns of this organism. Thus, the aim of this study was to evaluate the persistence of Staphylococcus aureus colonization at three body sites (vagina, nares, and anus) and serum antibody to toxic shock syndrome toxin-producing Staphylococcus aureus among a small group of healthy, menstruating women evaluated previously in a larger study. Methods: One year after the completion of that study, 311 subjects were recalled into 5 groups. Four samples were obtained from each participant at several visits over an additional 6-11 month period: 1) an anterior nares swab; 2) an anal swab; 3) a vagina swab; and 4) a blood sample. Gram stain, a catalase test, and a rapid S. aureus-specific latex agglutination test were performed to phenotypically identify S. aureus from sample swabs. A competitive ELISA was used to quantify TSST-1 production. Human TSST-1 IgG antibodies were determined from the blood samples using a sandwich ELISA method. Results: We found only 41% of toxigenic S. aureus and 35.5% of non-toxigenic nasal carriage could be classified as persistent. None of the toxigenic S. aureus vaginal or anal carriage could be classified as persistent. Despite the low persistence of S. aureus colonization, subjects colonized with a toxigenic strain were found to display distributions of antibody titers skewed toward higher titers than other subjects. Seven percent (5/75) of subjects became seropositive during recall, but none experienced toxic shock syndrome-like symptoms. Conclusions: Nasal carriage of S. aureus appears to be persistent and the best predicator of subsequent colonization, whereas vaginal and anal carriage appear to be more transient. From these findings, it appears that antibody titers in women found to be colonized with toxigenic S. aureus remained skewed toward higher titers whether or not the colonies were found to be persistent or transient in nature. This suggests that colonization at some point in time is sufficient to elevate antibody titer levels and those levels appear to be persistent. Results also indicate that women can become seropositive without experiencing signs or symptoms of toxic shock syndrome.

Background: Over-the-counter (OTC) feminine hygiene products come with little warning about possible side effects. This study evaluates in-vitro their effects on Lactobacillus crispatus, which is dominant in the normal vaginal microbiota and helps maintain a healthy mucosal barrier essential for normal reproductive function and prevention of sexually transmitted infections and gynecologic cancer. Methods: A feminine moisturizer (Vagisil), personal lubricant, and douche were purchased OTC. A topical spermicide (nonoxynol-9) known to alter the vaginal immune barrier was used as a control. L. crispatus was incubated with each product for 2 and 24h and then seeded on agar for colony forming units (CFU). Human vaginal epithelial cells were exposed to products in the presence or absence of L. crispatus for 24h, followed by epithelium-associated CFU enumeration. Interleukin-8 was immunoassayed and ANOVA was used for statistical evaluation. Results: Nonoxynol-9 and Vagisil suppressed Lactobacillus growth at 2h and killed all bacteria at 24h. The lubricant decreased bacterial growth insignificantly at 2h but killed all at 24h. The douche did not have a significant effect. At full strength, all products suppressed epithelial viability and all, except the douche, suppressed epithelial-associated CFU. When applied at non-toxic dose in the absence of bacteria, the douche and moisturizer induced an increase of IL-8, suggesting a potential to initiate inflammatory reaction. In the presence of L. crispatus, the proinflammatory effects of the douche and moisturizer were countered, and IL-8 production was inhibited in the presence of the other products. Conclusion: Some OTC vaginal products may be harmful to L. crispatus and alter the vaginal immune environment. Illustrated through these results, L. crispatus is essential in the preservation of the function of vaginal epithelial cells in the presence of some feminine hygiene products. More research should be invested toward these products before they are placed on the market.

Objectives: Complex interactions of vaginal microorganisms with the genital tract epithelium shape mucosal innate immunity, which holds the key to sexual and reproductive health. Bacterial vaginosis (BV), a microbiome-disturbance syndrome prevalent in reproductive-age women, occurs commonly in concert with trichomoniasis, and both are associated with increased risk of adverse reproductive outcomes and viral infections, largely attributable to inflammation. To investigate the causative relationships among inflammation, BV and trichomoniasis, we established a model of human cervicovaginal epithelial cells colonised by vaginal Lactobacillus isolates, dominant in healthy women, and common BV species (Atopobium vaginae, Gardnerella vaginalis and Prevotella bivia). Methods: Colonised epithelia were infected with Trichomonas vaginalis (TV) or exposed to purified TV virulence factors (membrane lipophosphoglycan (LPG), its ceramide-phosphoinositol-glycan core (CPI-GC) or the endosymbiont Trichomonas vaginalis virus (TVV)), followed by assessment of bacterial colony-forming units, the mucosal anti-inflammatory microbicide secretory leucocyte protease inhibitor (SLPI), and chemokines that drive pro-inflammatory, antigen-presenting and T cells. Results: TV reduced colonisation by Lactobacillus but not by BV species, which were found inside epithelial cells. TV increased interleukin (IL)-8 and suppressed SLPI, likely via LPG/CPI-GC, and upregulated IL-8 and RANTES, likely via TVV as suggested by use of purified pathogenic determinants. BV species A vaginae and G vaginalis induced IL-8 and RANTES, and also amplified the pro-inflammatory responses to both LPG/CPI-GC and TVV, whereas P bivia suppressed the TV/TVV-induced chemokines. Conclusions: These molecular host–parasite–endosymbiont–bacteria interactions explain epidemiological associations and suggest a revised paradigm for restoring vaginal immunity and preventing BV/TV-attributable inflammatory sequelae in women.

Background: A modest number of prospective studies of the composition of the intestinal microbiota and eczema in early life have yielded conflicting results. Objective: To examine the relationship between the bacterial diversity of the gut and the development of eczema in early life by methods other than stool culture. Methods: Fecal samples were collected from 21 infants at 1 and 4 months of life. Nine infants were diagnosed with eczema by the age of 6 months (cases) and 12 infants were not (controls). After conducting denaturating gradient gel electrophoresis (DGGE) of stool samples, we compared the microbial diversity of cases and controls using the number of electrophoretic bands and the Shannon index of diversity (H') as indicators. Results: Control subjects had significantly greater fecal microbial diversity than children with eczema at ages 1 (mean H' for controls = 0.75 vs. 0.53 for cases, P = 0.01) and 4 months (mean H' for controls = 0.92 vs. 0.59 for cases, P = 0.02). The increase in diversity from 1 to 4 months of age was significant in controls (P = 0.04) but not in children who developed eczema by 6 months of age (P = 0.32). Conclusion: Our findings suggest that reduced microbial diversity is associated with the development of eczema in early life.

Longitudinal studies of the microbiota are important for discovering changes in microbial communities that affect the host. The complexity of these ecosystems requires rigorous integrated experimental and computational methods to identify temporal signatures that promote physiologic or pathophysiologic responses in vivo. Employing a murine model of infectious colitis with the pathogen Citrobacter rodentium, we generated a 2-month time-series of 16S rDNA gene profiles, and quantitatively cultured commensals, from multiple intestinal sites in infected and uninfected mice. We developed a computational framework to discover time-varying signatures for individual taxa, and to automatically group signatures to identify microbial sub-communities within the larger gut ecosystem that demonstrate common behaviors. Application of this model to the 16S rDNA dataset revealed dynamic alterations in the microbiota at multiple levels of resolution, from effects on systems-level metrics to changes across anatomic sites for individual taxa and species. These analyses revealed unique, time-dependent microbial signatures associated with host responses at different stages of colitis. Signatures included a Mucispirillum OTU associated with early disruption of the colonic surface mucus layer, prior to the onset of symptomatic colitis, and members of the Clostridiales and Lactobacillales that increased with successful resolution of inflammation, after clearance of the pathogen. Quantitative culture data validated findings for predominant species, further refining and strengthening model predictions. These findings provide new insights into the complex behaviors found within host ecosystems, and define several time-dependent microbial signatures that may be leveraged in studies of other infectious or inflammatory conditions.

Leptotrichia species are normal constituents of the oral cavity and the genitourinary tract microbiota that are known to provoke disease in immunocompromised patients and rarely in immunocompetent individuals. Following the description of Leptotrichia goodfellowii sp. nov., two cases of endocarditis by this species have been reported. Here, we report a case of Leptotrichia goodfellowii endocarditis in an immunocompetent patient with a valvular allograft. The isolation and identification of Leptotrichia can be challenging, and it is likely that infection with this pathogen is significantly underdiagnosed. A definitive identification, as in this case, most often requires 16S rRNA gene sequencing, highlighting the increasingly important role of this diagnostic modality among immunocompetent patients with undetermined anaerobic bacteremia.

Background: Increasing evidence links altered intestinal flora in infancy to eczema and asthma. No studies have investigated the influence of maternal intestinal flora on wheezing and eczema in early childhood.

Objective: To investigate the link between maternal intestinal flora during pregnancy and development of wheeze and eczema in infancy.

Methods: Sixty pregnant women from the Boston area gave stool samples during the third trimester of their pregnancy and answered questions during pregnancy about their own health, and about their children’s health when the child was 2 and 6 months of age. Quantitative culture was performed on stool samples and measured in log10colony-forming units(CFU)/gram stool. Primary outcomes included infant wheeze and eczema in the first 6 months of life. Atopic wheeze, defined as wheeze and eczema, was analyzed as a secondary outcome.

Results: In multivariate models adjusted for breastfeeding, daycare attendance and maternal atopy, higher counts of maternal total aerobes (TA) and enterococci (E) were associated with increased risk of infant wheeze (TA: OR 2.32 for 1 log increase in CFU/g stool [95% CI 1.22, 4.42]; E: OR 1.57 [95% CI 1.06, 2.31]). No organisms were associated with either eczema or atopic wheeze.

Conclusions & Clinical Relevance: In our cohort, higher maternal total aerobes and enterococci were related to increased risk of infant wheeze. Maternal intestinal flora may be an important environmental exposure in early immune system development.