A40 GUT MICROBIOTA PROMOTES NUTRIENT AVAILABLITY AND PATHOGENESIS OF AN ATTACHING/ EFFACING BACTERIAL PATHOGEN

Background

Our gut microbiota plays an important role in protecting the gastrointestinal (GI) tract from invading enteric pathogens. Much of this colonization resistance is mediated by limiting nutrient availability, however, enteric pathogens have evolved strategies to subvert this competition, utilizing commensal metabolites to facilitate their infection. Access to nutrients is not only crucial for a pathogen’s metabolic fitness, but can also drive the expression of virulence factors, a process high in energy demands. In addition, enteric pathogens, such as the attaching and effacing (A/E) bacterium Citrobacter rodentium, must cross the colonic mucus layer that normally prevents their direct access to the underlying epithelium. Intestinal mucus is comprised of highly glycosylated mucins, with the sugar sialic acid frequently occupying the terminal position of their O-glycan side chains. We hypothesize that C. rodentium utilizes commensal-liberated mucin sugars, such as sialic acid, as nutrients and signals to promote its virulence.

Purpose

This study investigates the mechanisms by which A/E pathogens reach the colonic mucosal surface, and the role played by commensal microbes in facilitating the infection.

Method

Expression of virulence factors secreted by C. rodentium in the presence or absence of sialic acid was analyzed by SDS-PAGE and mass spectrometry. Next, we infected specific-pathogen free (SPF), germfree (GF), and previously GF C57Bl/6 mice mono-colonized with Bacteroides thetaotaomicron, a mucus-degrading commensal, to examine their susceptibility to C. rodentium and to measure the levels of free sialic acid in their feces.

Result(s)

Sensing of sialic acid by C. rodentium, was found to induce the secretion of several key virulence proteins, enhancing the pathogen’s migration across the colonic mucus layer and adhesion to the underlying epithelium. Access to sialic acid within the gut environment was enhanced in the presence of microbiota, as the levels of free sialic acid were low in GF mice. Interestingly, despite GF mice carrying very high C. rodentium burdens, passage across the mucus layer and infection of their colonic epithelium was impaired as compared to SPF mice. Notably, B. thetaotaomicron was found to degrade whole mucus in vitro, facilitating its consumption by C. rodentium for growth, while B. thetaotaomicron mono-colonized GF mice showed increased susceptibility to colonic infection by C. rodentium.

Conclusion(s)

We demonstrate that although commensal microbes promote colonization resistance, as an A/E pathogen infection establishes, specific commensal bacteria accelerate infection in the GI tract by releasing an important nutrient, ie. sialic acid, from mucus. Access to sialic acid promotes C. rodentium virulence by inducing the key virulence factors that facilitate its translocation across the mucus layer as well as adhesion to the epithelium, thereby expediting disease progression.

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CCC, CIHR, Other

Please indicate your source of funding;

CH.I.L.D. Foundation

Disclosure of Interest

None Declared

A15 GENETIC OR DIET-ASSOCIATED DEFECTS IN MUCUS FACILITATE ULCERATIVE COLITIS PATHOBIONT-DRIVEN COLITIS

Background

The Inflammatory Bowel Diseases (IBD), Crohn’s Disease (CD) and ulcerative colitis (UC) affect > 270,000 Canadians and are increasing in incidence. Ileal CD has been linked to the overgrowth of mucosal adherent E. coli. Recent studies have also implicated the adherence of Escherichia coli pathobionts to the colonic mucosa of UC patients. Using the representative UC E. coli pathobiont p19A, we recently demonstrated it aggravated chemical-induced colitis in susceptible mice, through the actions of the toxin alpha-hemolysin, and by adhering to the inflamed colonic mucosa via the adhesin FimH. It is less clear what host factors control susceptibility to the UC pathobionts. One of the potential candidates is the glycosylated mucin (Muc2) which forms the mucus layer that covers the colonic epithelium and is often impaired in UC patients.

Purpose

To define the role of mucus structure and function in determining susceptibility to the p19A pathobiont, and its ability to cause colitis in mice.

Method

In vitro growth was assessed to test p19A’s ability to utilize mucin-derived sugars as nutrients. Susceptibility to p19A was tested in two mouse models of colonic mucus impairment. The first is a mouse strain deficient in core 1 derived O-glycans in their intestinal epithelial cells (IEC C1galt1^-/-), resulting in reduced Muc2 glycosylation, and thus a thin and impaired mucus barrier. The second model involves feeding wildtype (WT) C57BL/6CR mice a fiber-free (FF) diet, resulting in a significantly thinner colonic mucus layer. The mice were subsequently orally gavaged with p19A and their susceptibility determined by p19A burdens, intestinal histopathology, inflammatory cytokine and short chain fatty acid (SCFA) production.

Result(s)

When tested in vitro, the p19A pathobiont was found to use an array of mucin-derived sugars as sole carbon source to proliferate. Following oral gavage of WT mice fed a normal diet, immunostaining identified p19A within the colonic mucus but it did not reach the colonic mucosa or cause disease. In contrast, p19A was found at the colonic mucosal surface of mucus-defective IEC C1galt1^-/- mice (as compared to IEC C1galt1^flox/flox mice) and in WT mice fed a fiber-free diet. This mucosal adherence was associated with increased body weight loss during the course of infection, as well as increased p19A burdens, colonic pathology and pro-inflammatory cytokine expression. Especially fiber-free diet-fed mice showed reduced SCFA levels in their feces at baseline. When the mice were given exogenous SCFA (tributyrin) orally, p19A infection was reduced.

Conclusion(s)

Our results indicate that UC E. coli pathobionts are able to dwell within colonic mucus and utilize mucin sugars as nutrients. Moreover, they can reach the mucosal surface and induce colitis in hosts suffering genetic or diet-based mucus dysfunction. In part, this susceptibility reflects the important role played by mucus in the production of SCFA, suggesting potential therapeutic approaches for patients suffering UC.

Please acknowledge all funding agencies by checking the applicable boxes below

CCC, CIHR

Disclosure of Interest

None Declared

[Progress in perioperative management of ABO-incompatible pediatric liver transplantation]

ABO incompatible(ABO-I) liver grafts will affect the prognosis of liver transplantation. With the improvement of perioperative treatment,including plasma exchange,rituximab,splenectomy,etc.,the prognosis of ABO-I liver transplantation has been greatly improved. Because children's immune systems are not fully developed,the perioperative management of ABO-I pediatric liver transplantation is significantly different from that of adults. Reducing the perioperative anti-donor ABO antibody titer is the key to the perioperative management of ABO-I liver transplantation. This article summarizes literatures on the perioperative management of ABO-I pediatric liver transplantation, including the perioperative anti-rejection regimen in pediatric recipients of different ages, splenectomy, postoperative monitoring and postoperative complications, etc.

[Clinical characteristics of 18 children with chronic nonbacterial osteomyelitis]

Objective: To investigate the clinical features of children with chronic nonbacterial osteomyelitis (CNO), and raise awareness among clinicians. Methods: In this retrospective study, 18 patients with CNO who were diagnosed in Children's Hospital of Fudan University from January 2015 to December 2021 were included. Results: Eighteen children with CNO (12 males, 6 females) were identified. Their age at onset was 9 (5, 11) years, the delay in diagnosis was 2 (1, 6) months, and follow-up-was 17 (8, 34) months. The most common symptoms were fever in 14 children, as well as bone pain and (or) arthralgia in 14 children. In terms of laboratory results, normal white blood cell counts were observed at onset in 17 patients; increased erythrocyte sedimentation rate (ESR) in all patients; increased C reactive protein (CRP) over the normal value in 14 patients. Of the 18 patients, 2 had positive antinuclear antibodies, while none had positive human leukocyte antigen-B27 or rheumatoid factor. Imaging examination revealed that all the patients had symmetrical and multifocal skeletal lesions. The number of structural lesions detected by imaging investigation was 8 (6, 11). The most frequently affected bones were tibia in 18 patients and femur in 17 patients. Bone biopsy was conducted in 14 patients and acute or chronic osteomyelitis manifested with inflammatory cells infiltration were detected. Magnetic resonance imaging (MRI) found bone lesions in all the patients and bone scintigraphy were positive in 13 patients. All the patients were treated with nonsteroidal anti-inflammatory drugs, among whom 10 cases also treated with oral glucocorticoids, 9 cases with traditional disease modifying anti-rheumatic drugs, 8 cases with bisphosphonates and 6 cases with tumor necrosis factor inhibitors. The pediatric chronic nonbacterial osteomyelitis disease activity score, increased by 70% or more in 13 patients within the initial 6-month follow-up. Conclusions: The clinical manifestations of CNO are lack of specificity. The first symptom of CNO is fever, with or without bone pain and (or) arthralgia, with normal peripheral blood leukocytes, elevated CRP and (or) ESR. Whole body bone scanning combined with MRI can early detect osteomyelitis at subclinical sites, and improve the diagnostic rate of CNO.

Effect of ventilation mode on postoperative pulmonary complications following lung resection surgery: a randomised controlled trial

The effect of intra-operative mechanical ventilation modes on pulmonary outcomes after thoracic surgery with one-lung ventilation has not been well established. We evaluated the impact of three common ventilation modes on postoperative pulmonary complications in patients undergoing lung resection surgery. In this two-centre randomised controlled trial, 1224 adults scheduled for lung resection surgery with one-lung ventilation were randomised to one of three groups: volume-controlled ventilation; pressure-controlled ventilation; and pressure-control with volume guaranteed ventilation. Enhanced recovery after surgery pathways and lung-protective ventilation protocols were implemented in all groups. The primary outcome was a composite of postoperative pulmonary complications within the first seven postoperative days. The outcome occurred in 270 (22%), with 87 (21%) in the volume control group, 89 (22%) in the pressure control group and 94 (23%) in the pressure-control with volume guaranteed group (p = 0.831). The secondary outcomes also did not differ across study groups. In patients undergoing lung resection surgery with one-lung ventilation, the choice of ventilation mode did not influence the risk of developing postoperative pulmonary complications. This is the first randomised controlled trial examining the effect of three ventilation modes on pulmonary outcomes in patients undergoing lung resection surgery.

Closing Post-orthodontic Spaces Between Anterior Teeth Using Sequential 3D-printed Direct Composite Injection Guides

Restorative treatment of anterior teeth is sometimes required to improve esthetic and functional occlusal outcomes of orthodontic therapy. This case report presents a direct, noninvasive approach to close post-orthodontic gaps in anterior teeth using a 3D-printed composite resin injection guide with a full digital workflow. The composite injection technique using 3D-printed guides is a full digital workflow that can transfer the design precisely, save chair time, and simplify the direct composite restoration procedure.

[A prospective cohort study on socioeconomic status and risk of all-cause mortality among patients with type 2 diabetes based on latent class analysis]

Objective: To investigate the relationship between socioeconomic status (SES) and all-cause mortality in patients with type 2 diabetes. Methods: A total of 17 553 patients with type 2 diabetes were recruited under the National Basic Public Health Service Project in Changshu county, Qingjiangpu district, and Huai'an district in Huai'an city of Jiangsu province as participants. Latent class analysis was applied to classify the individuals based on five socioeconomic indicators. Then, Cox proportional hazards regression models were used to estimate the associations of different levels of SES with all-cause mortality, and stratified analysis was performed according to age and area. Results: Among 100 529.08 person-years of the fo1low-up, the median follow-up time was 5.7 years, and 1 829 deaths occurred during the follow-up period. According to the relevant results of the latent class model, the model of the "three classes" was the best. The related population was then divided into low SES (8 256 people, 47.0%), medium SES (4 427 people, 25.2%), and high SES groups (4 870 people, 27.8%). Compared to patients with high SES, the multivariate-adjusted hazard ratio (95%CI) of all-cause mortality associated with low SES for males and females were 1.84 (1.53-2.21) and 1.41 (1.51-1.72), respectively. Stratified analysis showed that the hazard ration (95%CI) of all-cause mortality associated with low SES for males and females were 1.99 (1.12-2.95) and 2.01 (1.20-3.23), respectively, in people younger than 60 years old, and were 1.90 (1.57-2.31) and 1.40 (1.13-1.73) in people over 60 years old. The HR values (95%CI) for all-cause mortality associated with low SES for the male and females were 1.54 (1.17-2.04) and 1.27 (1.02-1.59) in the urban population with 2.11 (1.55-2.85) and 2.64 (1.17-3.35) in rural population, respectively. Conclusions: Lower SES increased the risk of all-cause mortality in type 2 diabetic patients, which is more significant in younger and rural populations.

Association of usual walking with mortality in oldest old adults aged 85 years and older: a nationwide senior cohort study

Background

Current guidelines recommend moderate to vigorous intensity physical activity (MVPA) for health benefit in adults. However, it is difficult to meet the recommended minimum MVPA in “oldest old” aged over 85. Although walking is simple and easy exercise for oldest old, research on the association between walking and mortality in oldest old are lacking.

Purpose

To investigate the association between walking and the risk of all-cause and cardiovascular mortality among older adults aged 85 years and older.

Methods

7047 participants aged 85 or older underwent the Korean National Health Screening Program, including self-administered questionnaire for physical activity. Reported frequency per week of walking for at least 30 minutes increment was used to classify hours of walking per week. We computed multivariable-adjusted hazard ratios for walking and mutually adjusted for MVPA in relation to all-cause and cardiovascular mortality.

Results

The proportions of participants who engaged in walking, moderate- and vigorous-intensity physical activity were 42.5% (2996/7047), 14.7% (1037/7047) and 11.0% (773/7047), respectively. Only 7.6% (538/7047) of participants met the guidelines recommended minimum MVPA. Compared to inactive individuals, those who walked at least 1 hour per week had lower all-cause (HR 0.60 [95% CI, 0.50–0.74]) and cardiovascular mortality risk (HR 0.61 [95% CI, 0.42–0.89]). Walking 1 hour per week was still significant associated with reduction of risk for all-cause (HR 0.50 [95% CI, 0.40–0.61]) and cardiovascular mortality (HR 0.46 [95% CI, 0.30–0.70]) among participants who reported only walking without any MVPA.

Conclusions

1 hour a week of walking might be of benefit for all-cause and cardiovascular mortality in aged over 85 years, even without MVPA. Promoting walking may be a way to help oldest old avoid inactivity and encourage an active lifestyle for all-cause and cardiovascular mortality risk reduction.

Funding Acknowledgement

Type of funding sources: None.

[A multicenter epidemiological study of acute bacterial meningitis in children]

Objective: To analyze the clinical epidemiological characteristics including composition of pathogens , clinical characteristics, and disease prognosis acute bacterial meningitis (ABM) in Chinese children. Methods: A retrospective analysis was performed on the clinical and laboratory data of 1 610 children <15 years of age with ABM in 33 tertiary hospitals in China from January 2019 to December 2020. Patients were divided into different groups according to age,<28 days group, 28 days to <3 months group, 3 months to <1 year group, 1-<5 years of age group, 5-<15 years of age group; etiology confirmed group and clinically diagnosed group according to etiology diagnosis. Non-numeric variables were analyzed with the Chi-square test or Fisher's exact test, while non-normal distrituction numeric variables were compared with nonparametric test. Results: Among 1 610 children with ABM, 955 were male and 650 were female (5 cases were not provided with gender information), and the age of onset was 1.5 (0.5, 5.5) months. There were 588 cases age from <28 days, 462 cases age from 28 days to <3 months, 302 cases age from 3 months to <1 year of age group, 156 cases in the 1-<5 years of age and 101 cases in the 5-<15 years of age. The detection rates were 38.8% (95/245) and 31.5% (70/222) of Escherichia coli and 27.8% (68/245) and 35.1% (78/222) of Streptococcus agalactiae in infants younger than 28 days of age and 28 days to 3 months of age; the detection rates of Streptococcus pneumonia, Escherichia coli, and Streptococcus agalactiae were 34.3% (61/178), 14.0% (25/178) and 13.5% (24/178) in the 3 months of age to <1 year of age group; the dominant pathogens were Streptococcus pneumoniae and the detection rate were 67.9% (74/109) and 44.4% (16/36) in the 1-<5 years of age and 5-<15 years of age . There were 9.7% (19/195) strains of Escherichia coli producing ultra-broad-spectrum β-lactamases. The positive rates of cerebrospinal fluid (CSF) culture and blood culture were 32.2% (515/1 598) and 25.0% (400/1 598), while 38.2% (126/330)and 25.3% (21/83) in CSF metagenomics next generation sequencing and Streptococcus pneumoniae antigen detection. There were 4.3% (32/790) cases of which CSF white blood cell counts were normal in etiology confirmed group. Among 1 610 children with ABM, main intracranial imaging complications were subdural effusion and (or) empyema in 349 cases (21.7%), hydrocephalus in 233 cases (14.5%), brain abscess in 178 cases (11.1%), and other cerebrovascular diseases, including encephalomalacia, cerebral infarction, and encephalatrophy, in 174 cases (10.8%). Among the 166 cases (10.3%) with unfavorable outcome, 32 cases (2.0%) died among whom 24 cases died before 1 year of age, and 37 cases (2.3%) had recurrence among whom 25 cases had recurrence within 3 weeks. The incidences of subdural effusion and (or) empyema, brain abscess and ependymitis in the etiology confirmed group were significantly higher than those in the clinically diagnosed group (26.2% (207/790) vs. 17.3% (142/820), 13.0% (103/790) vs. 9.1% (75/820), 4.6% (36/790) vs. 2.7% (22/820), χ²=18.71, 6.20, 4.07, all P<0.05), but there was no significant difference in the unfavorable outcomes, mortility, and recurrence between these 2 groups (all P>0.05). Conclusions: The onset age of ABM in children is usually within 1 year of age, especially <3 months. The common pathogens in infants <3 months of age are Escherichia coli and Streptococcus agalactiae, and the dominant pathogen in infant ≥3 months is Streptococcus pneumoniae. Subdural effusion and (or) empyema and hydrocephalus are common complications. ABM should not be excluded even if CSF white blood cell counts is within normal range. Standardized bacteriological examination should be paid more attention to increase the pathogenic detection rate. Non-culture CSF detection methods may facilitate the pathogenic diagnosis.

[Outcome of pediatric-to-adult liver transplantation:a single-center study in China]

Objective: To explore the outcome of the pediatric-to-adult liver transplantation, including postoperative complications and relevant factors which affecting graft survival. Methods: Data of 55 patients undergoing pediatric-to-adult liver transplantation at the First Affiliated Hospital of Zhejiang University between January 2015 and August 2021 were retrospectively analyzed. The donors consisted of 34 males and 21 females, and the age was (11.8±4.7) years (range: 1 to 17 years). Among the cases,17 cases (30.9%) were donation of brain death,32 cases (58.2%) were donation of cardiac death, and 6 cases (10.9%) were donation after brain death plus cardiac death. The recipients consisted of 32 males and 23 females, and the age was (51.6±10.1) years (range: 27 to 70 years). Among the recipients,10 cases (18.2%) were ABO-incompatible liver transplantation.The influencing factors of early graft survival were analyzed by Student t test,Mann-Whitney U test or χ² test,respectively.Survival curve was drawn by Kaplan-Meier method.Logistic multivariate analysis was used to analyze the independent relevant factors of early postoperative graft loss. Results: Up to October 31,2021,the follow-up time (M(IQR)) was 36.0(43.1)months(range:5.9 to 81.7 months).There were 13 cases with graft loss (two of them underwent re-transplantation due to acute liver failure).The monofactor analysis indicated that cold ischemia time and donor-recipient blood group matching were the relevant factors affecting the early graft survival rate(both P<0.05).Logistic multivariate analysis showed that cold ischemia time and history of recipient gastrointestinal bleeding were independent relevant factors(both P<0.05).Postoperative hepatic artery thrombosis occurred in 3 cases(5.5%), portal vein thrombosis diagnosed in 4 cases(7.3%), portal vein stenosis occurred in 2 cases(3.6%),biliary complications diagnosed in 7 cases(12.7%), and small liver syndrome was found in 8 cases(14.5%). Conclusions: Adult liver transplantation with pediatric donor liver is an effective method to treat end-stage liver disease.Cold ischemia time and history of recipient gastrointestinal bleeding were independent relevant factors for the early graft survival.