Diet-driven differential response of Akkermansia muciniphila modulates pathogen susceptibility.

The erosion of the colonic mucus layer by a dietary fiber-deprived gut microbiota results in heightened susceptibility to an attaching and effacing pathogen, Citrobacter rodentium. Nevertheless, the questions of whether and how specific mucolytic bacteria aid in the increased pathogen susceptibility remain unexplored. Here, we leverage a functionally characterized, 14-member synthetic human microbiota in gnotobiotic mice to deduce which bacteria and functions are responsible for the pathogen susceptibility. Using strain dropouts of mucolytic bacteria from the community, we show that Akkermansia muciniphila renders the host more vulnerable to the mucosal pathogen during fiber deprivation. However, the presence of A. muciniphila reduces pathogen load on a fiber-sufficient diet, highlighting the context-dependent beneficial effects of this mucin specialist. The enhanced pathogen susceptibility is not owing to altered host immune or pathogen responses, but is driven by a combination of increased mucus penetrability and altered activities of A. muciniphila and other community members. Our study provides novel insights into the mechanisms of how discrete functional responses of the same mucolytic bacterium either resist or enhance enteric pathogen susceptibility.

Concentrated Raw Fibers Enhance the Fiber-Degrading Capacity of a Synthetic Human Gut Microbiome.

The consumption of prebiotic fibers to modulate the human gut microbiome is a promising strategy to positively impact health. Nevertheless, given the compositional complexity of the microbiome and its inter-individual variances, generalized recommendations on the source or amount of fiber supplements remain vague. This problem is further compounded by availability of tractable in vitro and in vivo models to validate certain fibers. We employed a gnotobiotic mouse model containing a 14-member synthetic human gut microbiome (SM) in vivo, characterized a priori for their ability to metabolize a collection of fibers in vitro. This SM contains 14 different strains belonging to five distinct phyla. Since soluble purified fibers have been a common subject of studies, we specifically investigated the effects of dietary concentrated raw fibers (CRFs)-containing fibers from pea, oat, psyllium, wheat and apple-on the compositional and functional alterations in the SM. We demonstrate that, compared to a fiber-free diet, CRF supplementation increased the abundance of fiber-degraders, namely Eubacterium rectale, Roseburia intestinalis and Bacteroides ovatus and decreased the abundance of the mucin-degrader Akkermansia muciniphila. These results were corroborated by a general increase of bacterial fiber-degrading α-glucosidase enzyme activity. Overall, our results highlight the ability of CRFs to enhance the microbial fiber-degrading capacity.

The impact of ambient operating room temperature on neonatal and maternal hypothermia and associated morbidities: a randomized controlled trial.

BACKGROUND: Neonatal hypothermia is common at the time of cesarean delivery and has been associated with a constellation of morbidities in addition to increased neonatal mortality. Additionally, maternal hypothermia is often uncomfortable for the surgical patient and has been associated with intraoperative and postoperative complications. Various methods to decrease the rates of neonatal and maternal hypothermia have been examined and found to have varying levels of success. OBJECTIVE: We sought to determine whether an increase in operating room temperature at cesarean delivery results in a decrease in the rate of neonatal hypothermia and associated morbidities. STUDY DESIGN: In this single-center randomized trial, operating room temperatures were adjusted weekly according to a cluster randomization schedule to either 20°C (67°F), which was the standard at our institution, or 23°C (73°F), which was the maximum temperature allowable per hospital policy. Neonatal hypothermia was defined as core body temperature <36.5°C (97.7°F) per World Health Organization criteria. The primary study outcome was neonatal hypothermia on arrival to the admitting nursery. Measures of neonatal morbidity potentially associated with hypothermia were examined. RESULTS: From February through July 2015, 791 women who underwent cesarean deliveries were enrolled, resulting in 410 infants in the 20°C standard management group and 399 in the 23°C study group. The rate of neonatal hypothermia on arrival to the admitting nursery was lower in the study group as compared to the standard management group: 35% vs 50%, P < .001. Moderate to severe hypothermia was infrequent when the operating room temperature was 23°C (5%); in contrast such hypothermia occurred in 19% of the standard management group, P < .001. Additionally, neonatal temperature in the operating room immediately following delivery and stabilization was also higher in the study group, 37.1 ± 0.6°C vs 36.9 ± 0.6°C, P < .001. We found no difference in rates of intubation, ventilator use, hypoglycemia, metabolic acidemia, or intraventricular hemorrhage. Fever (temperature >38.0°C or 100.4°F) on arrival to the admitting unit was uncommon and did not differ between the study groups. Maternal temperature on arrival to the operating room was not different between the 2 groups, however by delivery it was significantly lower in the standard management group, 36.2 ± 0.6°C vs 36.4 ± 0.6°C, P < .001. This effect persisted, as maternal temperature on arrival to the postoperative care area was lower in the standard management group, 36.1 ± 0.6°C vs 36.2 ± 0.6°C, P < .001, and the rate of hypothermia was higher, 77% vs 69%, P = .008. CONCLUSION: A modest increase in operating room temperature at the time of cesarean reduces the rate of neonatal and maternal hypothermia. We did not detect a decrease in neonatal morbidity, but the power to detect a small change in these outcomes was limited.

A randomized control trial of bupivacaine and fentanyl versus fentanyl-only for epidural analgesia during the second stage of labor.

BACKGROUND: The purpose of this prospective, double-blinded, parallel-arm, randomized trial was to examine the effects of epidural bupivacaine on the length of the second stage of labor in nulliparous women. METHODS: The authors assessed length of second-stage labor, degree of motor blockade, mode of delivery, and visual analog scores in 310 nulliparous women with labor epidurals randomized to receive either: (1) 0.125% bupivacaine and fentanyl 2 µg/ml or (2) fentanyl 10 µg/ml alone via epidural using double blinding. RESULTS: The median duration of the second stage was 75 min (41, 128) in the bupivacaine/fentanyl group versus 73 min (42, 120) in the fentanyl-only group (P = 0.17) with a median difference of 6.0 (95% CI, -6.0 to 18.0). Furthermore, there was no difference in degree of motor blockade, incidence of operative delivery, visual analog scores, or neonatal outcomes between the two groups. No adverse events were reported. CONCLUSIONS: Use of epidural bupivacaine/fentanyl or a fentanyl-only infusion during the second stage of labor did not affect the duration of the second stage of labor, degree of motor blockade, mode of delivery, pain relief, and maternal or neonatal outcomes. However, in the fentanyl-only infusion group, there was a fivefold increase in opioid exposure to the fetus with unknown effects on neurobehavior, an outcome not assessed beyond the immediate postnatal period in this study.

Continuous Spinal Analgesia for Labor and Delivery: An Observational Study with a 23-Gauge Spinal Catheter.

BACKGROUND: The aim of the study was to assess postdural puncture headache, pain relief, motor blockade, and success rate of conversion to cesarean delivery anesthesia of a 23-gauge spinal catheter (Wiley Spinal®) for labor analgesia. METHODS: After insertion of the spinal catheter, intrathecal bupivacaine 2.5 mg was administered, followed by patient-controlled intrathecal analgesia (basal infusion of 0.0625% bupivacaine with fentanyl 2 µg/mL at a rate of 2 mL/h, demand bolus 1 mL, lockout interval 20 minutes). Bupivacaine 0.5%, up to 25 mg, was administered via the catheter along with fentanyl 20 µg for cesarean delivery anesthesia, if necessary. The catheter was removed after delivery or after 12 hours, whichever was longer. RESULTS: One hundred thirteen women were enrolled. In 12 women (11%), the catheter was not successfully inserted or maintained in position. Continuous spinal analgesia was used in 101 women. Three women (2.6%, 95% confidence interval, 0.7%-8.1%) developed postdural puncture headache. There were 83 spontaneous, 12 operative vaginal, and 18 cesarean deliveries. Of the 18 cesarean deliveries, 16 had continuous spinal analgesia when the decision was made to perform a cesarean delivery; conversion from labor analgesia to cesarean anesthesia was successful in 15 women (94%, 95% confidence interval, 67.7%-99.7%). CONCLUSIONS: The 23-gauge spinal catheter can be used for analgesia for labor. It can also be converted to surgical anesthesia for cesarean deliveries. Further studies are warranted to determine whether the spinal catheter will be a useful addition to the neuraxial techniques available for obstetric anesthesia care.

Active Warming during Cesarean Delivery: Should We SCIP It?

BACKGROUND: The purpose of this open, cluster randomized controlled trial was to evaluate whether use of a fiber optic-regulated warming mattress would decrease the incidence of hypothermia in women undergoing cesarean delivery. PATIENTS AND METHODS: A total of 484 women were randomized via the cluster method on a rotating weekly basis allocating participants to either use of the warming mattress or the standard method of warming at Parkland Hospital (heat-retaining caps, warmed intravenous and irrigation fluids, and warmed blankets). The primary outcome of interest was maternal hypothermia. Surgical site infections and neonatal outcomes were also assessed. RESULTS: The incidence of maternal hypothermia at the conclusion of the surgery was decreased in the warming mattress group, 67 versus 80% in the standard method group (p = 0.013). There were no significant differences in maternal hypothermia at delivery or on arrival to the postanesthesia care unit. The difference in surgical site infections and neonatal outcomes were nonsignificant. CONCLUSION: Use of a warming mattress reduced the incidence of maternal hypothermia at the conclusion of surgery; however, on admission to the postanesthesia care unit, these effects had dissipated.

Non-SCFA microbial metabolites associated with fiber fermentation and host health.

Dietary fiber is degraded by commensal gut microbes to yield host-beneficial short-chain fatty acids (SCFAs), but personalized responses to fiber supplementation highlight a role for other microbial metabolites in shaping host health. In this review we summarize recent findings from dietary fiber intervention studies describing health impacts attributed to microbial metabolites other than SCFAs, particularly secondary bile acids (2°BAs), aromatic amino acid derivatives, neurotransmitters, and B vitamins. We also discuss shifts in microbial metabolism occurring through altered maternal dietary fiber intake and agricultural practices, which warrant further investigation. To optimize the health benefits of dietary fibers, it is essential to survey a range of metabolites and adapt recommendations on a personalized basis, according to the different functional aspects of the microbiome.

Gut microbial factors predict disease severity in a mouse model of multiple sclerosis.

Gut bacteria are linked to neurodegenerative diseases but the risk factors beyond microbiota composition are limited. Here we used a pre-clinical model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), to identify microbial risk factors. Mice with different genotypes and complex microbiotas or six combinations of a synthetic human microbiota were analysed, resulting in varying probabilities of severe neuroinflammation. However, the presence or relative abundances of suspected microbial risk factors failed to predict disease severity. Akkermansia muciniphila, often associated with MS, exhibited variable associations with EAE severity depending on the background microbiota. Significant inter-individual disease course variations were observed among mice harbouring the same microbiota. Evaluation of microbial functional characteristics and host immune responses demonstrated that the immunoglobulin A coating index of certain bacteria before disease onset is a robust individualized predictor of disease development. Our study highlights the need to consider microbial community networks and host-specific bidirectional interactions when aiming to predict severity of neuroinflammation.

Opposing diet, microbiome, and metabolite mechanisms regulate inflammatory bowel disease in a genetically susceptible host.

Inflammatory bowel diseases (IBDs) are chronic conditions characterized by periods of spontaneous intestinal inflammation and are increasing in industrialized populations. Combined with host genetics, diet and gut bacteria are thought to contribute prominently to IBDs, but mechanisms are still emerging. In mice lacking the IBD-associated cytokine, interleukin-10, we show that a fiber-deprived gut microbiota promotes the deterioration of colonic mucus, leading to lethal colitis. Inflammation starts with the expansion of natural killer cells and altered immunoglobulin-A coating of some bacteria. Lethal colitis is then driven by Th1 immune responses to increased activities of mucin-degrading bacteria that cause inflammation first in regions with thinner mucus. A fiber-free exclusive enteral nutrition diet also induces mucus erosion but inhibits inflammation by simultaneously increasing an anti-inflammatory bacterial metabolite, isobutyrate. Our findings underscore the importance of focusing on microbial functions-not taxa-contributing to IBDs and that some diet-mediated functions can oppose those that promote disease.

The duplication 17p13.3 phenotype: analysis of 21 families delineates developmental, behavioral and brain abnormalities, and rare variant phenotypes.

Chromosome 17p13.3 is a gene rich region that when deleted is associated with the well-known Miller-Dieker syndrome. A recently described duplication syndrome involving this region has been associated with intellectual impairment, autism and occasional brain MRI abnormalities. We report 34 additional patients from 21 families to further delineate the clinical, neurological, behavioral, and brain imaging findings. We found a highly diverse phenotype with inter- and intrafamilial variability, especially in cognitive development. The most specific phenotype occurred in individuals with large duplications that include both the YWHAE and LIS1 genes. These patients had a relatively distinct facial phenotype and frequent structural brain abnormalities involving the corpus callosum, cerebellar vermis, and cranial base. Autism spectrum disorders were seen in a third of duplication probands, most commonly in those with duplications of YWHAE and flanking genes such as CRK. The typical neurobehavioral phenotype was usually seen in those with the larger duplications. We did not confirm the association of early overgrowth with involvement of YWHAE and CRK, or growth failure with duplications of LIS1. Older patients were often overweight. Three variant phenotypes included cleft lip/palate (CLP), split hand/foot with long bone deficiency (SHFLD), and a connective tissue phenotype resembling Marfan syndrome. The duplications in patients with clefts appear to disrupt ABR, while the SHFLD phenotype was associated with duplication of BHLHA9 as noted in two recent reports. The connective tissue phenotype did not have a convincing critical region. Our experience with this large cohort expands knowledge of this diverse duplication syndrome.

Ultrasound-guided transversus abdominal plane block with multimodal analgesia for pain management after total abdominal hysterectomy.

BACKGROUND: Transversus abdominis plane (TAP) block has been shown to provide pain relief after abdominal procedures. However, TAP block combined with multimodal analgesia technique have not been assessed in a randomized controlled trial. This randomized, controlled, observer-blinded study was designed to evaluate the analgesic efficacy of bilateral ultrasound-guided TAP blocks with or without acetaminophen and non-steroidal anti-inflammatory drug (NSAID) combination. METHODS: Patients undergoing total abdominal hysterectomy were randomized to one of three groups. Group 1 (n = 25) received a TAP block and ketorolac 30 mg, IV at the end of surgery and then ketorolac plus paracetamol 650 mg, orally, every 6 h for 24 h. Group 2 (n = 24) received only TAP block at the end of surgery. Group 3 (n = 25) received ketorolac 30 mg, IV at the end of surgery and then ketorolac plus paracetamol 650 mg, orally, every 6 h for 24 h. All patients received IV-PCA morphine for 24-h, postoperatively. All patients received a standardized general anaesthetic technique and dexamethasone 4 mg and ondansetron 4 mg, IV for antiemetic prophylaxis. RESULTS: There were no statistically significant differences in pain at rest between the groups. However, the pain on coughing (dynamic pain) in Group 1 was significantly less variable, compared with the other two groups (P = 0.012). Opioid consumption and occurrences of nausea, vomiting, and rescue antiemetic were similar in three the groups. CONCLUSIONS: The combination of TAP block and acetaminophen and NSAID provided less variability in dynamic pain compared with either treatment alone.

Maternal diet and gut microbiome composition modulate early-life immune development.

In early life, the intestinal mucosa and immune system undergo a critical developmental process to contain the expanding gut microbiome while promoting tolerance toward commensals, yet the influence of maternal diet and microbial composition on offspring immune maturation remains poorly understood. We colonized germ-free mice with a consortium of 14 strains, fed them a standard fiber-rich chow or a fiber-free diet, and then longitudinally assessed offspring development during the weaning period. Unlike pups born to dams fed the fiber-rich diet, pups of fiber-deprived dams demonstrated delayed colonization with Akkermansia muciniphila, a mucin-foraging bacterium that can also use milk oligosaccharides. The pups of fiber-deprived dams exhibited an enrichment of colonic transcripts corresponding to defense response pathways and a peak in Il22 expression at weaning. Removal of A. muciniphila from the community, but maintenance on the fiber-rich diet, was associated with reduced proportions of RORγt-positive innate and adaptive immune cell subsets. Our results highlight the potent influence of maternal dietary fiber intake and discrete changes in microbial composition on the postnatal microbiome assemblage and early immune development.

Diet-driven differential response of Akkermansia muciniphila modulates pathogen susceptibility.

The erosion of the colonic mucus layer by a dietary fiber-deprived gut microbiota results in heightened susceptibility to an attaching and effacing pathogen, Citrobacter rodentium. Nevertheless, the questions of whether and how specific mucolytic bacteria aid in the increased pathogen susceptibility remain unexplored. Here, we leverage a functionally characterized, 14-member synthetic human microbiota in gnotobiotic mice to deduce which bacteria and functions are responsible for the pathogen susceptibility. Using strain dropouts of mucolytic bacteria from the community, we show that Akkermansia muciniphila renders the host more vulnerable to the mucosal pathogen during fiber deprivation. However, the presence of A. muciniphila reduces pathogen load on a fiber-sufficient diet, highlighting the context-dependent beneficial effects of this mucin specialist. The enhanced pathogen susceptibility is not owing to altered host immune or pathogen responses, but is driven by a combination of increased mucus penetrability and altered activities of A. muciniphila and other community members. Our study provides novel insights into the mechanisms of how discrete functional responses of the same mucolytic bacterium either resist or enhance enteric pathogen susceptibility.

Akkermansia muciniphila exacerbates food allergy in fibre-deprived mice.

Alterations in the gut microbiome, including diet-driven changes, are linked to the rising prevalence of food allergy. However, little is known about how specific gut bacteria trigger the breakdown of oral tolerance. Here we show that depriving specific-pathogen-free mice of dietary fibre leads to a gut microbiota signature with increases in the mucin-degrading bacterium Akkermansia muciniphila. This signature is associated with intestinal barrier dysfunction, increased expression of type 1 and 2 cytokines and IgE-coated commensals in the colon, which result in an exacerbated allergic reaction to food allergens, ovalbumin and peanut. To demonstrate the causal role of A. muciniphila, we employed a tractable synthetic human gut microbiota in gnotobiotic mice. The presence of A. muciniphila within the microbiota, combined with fibre deprivation, resulted in stronger anti-commensal IgE coating and innate type-2 immune responses, which worsened symptoms of food allergy. Our study provides important insights into how gut microbes can regulate immune pathways of food allergy in a diet-dependent manner.

Unravelling specific diet and gut microbial contributions to inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic condition characterized by periods of spontaneous intestinal inflammation and is increasing in industrialized populations. Combined with host genetic predisposition, diet and gut bacteria are thought to be prominent features contributing to IBD, but little is known about the precise mechanisms involved. Here, we show that low dietary fiber promotes bacterial erosion of protective colonic mucus, leading to lethal colitis in mice lacking the IBD-associated cytokine, interleukin-10. Diet-induced inflammation is driven by mucin-degrading bacteria-mediated Th1 immune responses and is preceded by expansion of natural killer T cells and reduced immunoglobulin A coating of some bacteria. Surprisingly, an exclusive enteral nutrition diet, also lacking dietary fiber, reduced disease by increasing bacterial production of isobutyrate, which is dependent on the presence of a specific bacterial species, Eubacterium rectale. Our results illuminate a mechanistic framework using gnotobiotic mice to unravel the complex web of diet, host and microbial factors that influence IBD.

Glycemic control during labor and delivery: a survey of academic centers in the United States.

PURPOSE: Significant controversy surrounds the management of blood glucose levels during labor and delivery. The American College of Obstetrics and Gynecology has recommended "tight" blood glucose control (<110 mg/dL). However, there is concern that tight control can increase the incidence of maternal hypoglycemia. Thus, there remains a lack of consensus regarding glycemic control during labor and delivery. To assess the current intrapartum glycemic management, we surveyed obstetrical residency programs in the United States. METHODS: Questionnaires were distributed via email and if there was no response within 3 weeks, they were mailed to obstetrics/gynecology residency program directors. RESULTS: Of the 117 questionnaires distributed, 49 responses (41.9%) were received, but one was excluded, as it was incomplete. Although 85% of responders reported having a written protocol in place regarding intrapartum BG management, there was significant variation in target blood glucose levels, maintenance of those levels, monitoring of glucose levels, and fluid management during labor and delivery. CONCLUSION: The key finding of our survey is that there is significant variation in blood glucose management during labor and delivery. This survey identifies areas for improvement as well as areas for future research. Given the sparse obstetrical literature, properly conducted trials are necessary to assess all aspects of optimal intrapartum glucose management.

Quantitative assay to detect bacterial glycan-degrading enzyme activities in mouse and human fecal samples.

The gut microbiome expresses a multitude of enzymes degrading polysaccharides in dietary plant fibers and in host-secreted mucus. The quantitative detection of these glycan-degrading enzymes in fecal samples is important to elucidate the functional activity of the microbiome in health and disease. We describe a protocol for detection of glycan-degrading enzyme activity in mouse and human fecal samples, namely sulfatase and four carbohydrate-active enzymes. Assessing their activity can inform treatment strategies for diseases linked to the gut microbiome. For complete details on the use and execution of this protocol, please refer to Desai et al. (2016).

Constructing a gnotobiotic mouse model with a synthetic human gut microbiome to study host-microbe cross talk.

Reproducible in vivo models are necessary to address functional aspects of the gut microbiome in various diseases. Here, we present a gnotobiotic mouse model that allows for the investigation of specific microbial functions within the microbiome. We describe how to culture 14 different well-characterized human gut species and how to verify their proper colonization in germ-free mice. This protocol can be modified to add or remove certain species of interest to investigate microbial mechanistic details in various disease models. For complete details on the use and execution of this protocol, please refer to Desai et al. (2016).

Leveraging diet to engineer the gut microbiome.

Autoimmune diseases, including inflammatory bowel disease, multiple sclerosis and rheumatoid arthritis, have distinct clinical presentations but share underlying patterns of gut microbiome perturbation and intestinal barrier dysfunction. Their potentially common microbial drivers advocate for treatment strategies aimed at restoring appropriate microbiome function, but individual variation in host factors makes a uniform approach unlikely. In this Perspective, we consolidate knowledge on diet-microbiome interactions in local inflammation, gut microbiota imbalance and host immune dysregulation. By understanding and incorporating the effects of individual dietary components on microbial metabolic output and host physiology, we examine the potential for diet-based therapies for autoimmune disease prevention and treatment. We also discuss tools targeting the gut microbiome, such as faecal microbiota transplantation, probiotics and orthogonal niche engineering, which could be optimized using custom dietary interventions. These approaches highlight paths towards leveraging diet for precise engineering of the gut microbiome at a time of increasing autoimmune disease.

Deprivation of dietary fiber in specific-pathogen-free mice promotes susceptibility to the intestinal mucosal pathogen Citrobacter rodentium.

The change of dietary habits in Western societies, including reduced consumption of fiber, is linked to alterations in gut microbial ecology. Nevertheless, mechanistic connections between diet-induced microbiota changes that affect colonization resistance and enteric pathogen susceptibility are still emerging. We sought to investigate how a diet devoid of soluble plant fibers impacts the structure and function of a conventional gut microbiota in specific-pathogen-free (SPF) mice and how such changes alter susceptibility to a rodent enteric pathogen. We show that absence of dietary fiber intake leads to shifts in the abundances of specific taxa, microbiome-mediated erosion of the colonic mucus barrier, a reduction of intestinal barrier-promoting short-chain fatty acids, and increases in markers of mucosal barrier integrity disruption. Importantly, our results highlight that these low-fiber diet-induced changes in the gut microbial ecology collectively contribute to a lethal colitis by the mucosal pathogen Citrobacter rodentium, which is used as a mouse model for enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively). Our study indicates that modern, low-fiber Western-style diets might make individuals more prone to infection by enteric pathogens via the disruption of mucosal barrier integrity by diet-driven changes in the gut microbiota, illustrating possible implications for EPEC and EHEC infections.