A Computational Method to Dissect Colonization Resistance of the Gut Microbiota against Pathogens

The indigenous gut microbes have co-evolved with their hosts for millions of years. Those gut microbes play a crucial role in host health and disease. In particular, they protect the host against incursion by exogenous and often harmful microorganisms, a mechanism known as colonization resistance (CR). Yet, identifying the exact microbes responsible for the gut microbiota-mediated CR against a particular pathogen remains a fundamental challenge in microbiome research. Here, we develop a computational method --- Generalized Microbe-Phenotype Triangulation (GMPT) to systematically identify causal microbes that directly influence the microbiota-mediated CR against a pathogen. We systematically validate GMPT using a classical population dynamics model in community ecology, and then apply it to microbiome data from two mouse studies on C. difficile infection. The developed method will not only significantly advance our understanding of CR mechanisms but also pave the way for the rational design of microbiome-based therapies for preventing and treating enteric infections.

Mechanism of the Gut Microbiota Colonization Resistance and Enteric Pathogen Infection

The mammalian gut microbial community, known as the gut microbiota, comprises trillions of bacteria, which co-evolved with the host and has an important role in a variety of host functions that include nutrient acquisition, metabolism, and immunity development, and more importantly, it plays a critical role in the protection of the host from enteric infections associated with exogenous pathogens or indigenous pathobiont outgrowth that may result from healthy gut microbial community disruption. Microbiota evolves complex mechanisms to restrain pathogen growth, which included nutrient competition, competitive metabolic interactions, niche exclusion, and induction of host immune response, which are collectively termed colonization resistance. On the other hand, pathogens have also developed counterstrategies to expand their population and enhance their virulence to cope with the gut microbiota colonization resistance and cause infection. This review summarizes the available literature on the complex relationship occurring between the intestinal microbiota and enteric pathogens, describing how the gut microbiota can mediate colonization resistance against bacterial enteric infections and how bacterial enteropathogens can overcome this resistance as well as how the understanding of this complex interaction can inform future therapies against infectious diseases.

Alteration of Salmonella enterica Virulence and Host Pathogenesis through Targeting sdiA by Using the CRISPR-Cas9 System

Salmonella enterica is a common cause of many enteric infections worldwide and is successfully engineered to deliver heterologous antigens to be used as vaccines. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) RNA-guided Cas9 endonuclease is a promising genome editing tool. In the current study, a CRISPR-Cas9 system was used to target S.enterica sdiA that encodes signal molecule receptor SdiA and responds to the quorum sensing (QS) signaling compounds N-acylhomoserine lactones (AHLs). For this purpose, sdiA was targeted in both S.enterica wild type (WT) and the ΔssaV mutant strain, where SsaV has been reported to be an essential component of SPI2-T3SS. The impact of sdiA mutation on S. enterica virulence was evaluated at both early invasion and later intracellular replication in both the presence and absence of AHL. Additionally, the influence of sdiA mutation on the pathogenesis S. enterica WT and mutants was investigated in vivo, using mice infection model. Finally, the minimum inhibitory concentrations (MICs) of various antibiotics against S. enterica strains were determined. Present findings show that mutation in sdiA significantly affects S.enterica biofilm formation, cell adhesion and invasion. However, sdiA mutation did not affect bacterial intracellular survival. Moreover, in vivo bacterial pathogenesis was markedly lowered in S.enterica ΔsdiA in comparison with the wild-type strain. Significantly, double-mutant sdiA and ssaV attenuated the S. enterica virulence and in vivo pathogenesis. Moreover, mutations in selected genes increased Salmonella susceptibility to tested antibiotics, as revealed by determining the MICs and MBICs of these antibiotics. Altogether, current results clearly highlight the importance of the CRISPR-Cas9 system as a bacterial genome editing tool and the valuable role of SdiA in S.enterica virulence. The present findings extend the understanding of virulence regulation and host pathogenesis of Salmonellaenterica.

Cognitive Outcomes at 18 Months: Findings from the Early Life Interventions for Childhood Growth and Development in Tanzania (ELICIT) Trial

Micronutrient deficiencies and enteric infections negatively impact child growth and development. We enrolled children shortly after birth in a randomized, placebo-controlled, 2 × 2 factorial interventional trial in Haydom, Tanzania, to assess nicotinamide and/or antimicrobials (azithromycin and nitazoxanide) effect on length at 18 months of age. Cognitive score at 18 months using the Malawi Developmental Assessment Tool (MDAT), which includes gross motor, fine motor, language, and social assessments, was a secondary outcome. Here, we present the MDAT results of 1,032 children. There was no effect of nicotinamide (change in development-for-age Z score [DAZ] −0.08; 95% CI: −0.16, 0) or antimicrobials (change in DAZ 0.04; 95% CI: −0.06, 0.13) on overall MDAT score. The interventions had no effect on cognitive outcomes in subgroups defined by gender, socioeconomic status, birthweight, and birth season or on MDAT subscores. Further analyses are needed to identify targetable risk factors for impaired cognitive development in these settings.

Pan-Genome Reverse Vaccinology Approach for the Design of Multi-Epitope Vaccine Construct against Escherichia albertii

Escherichia albertii is characterized as an emerging pathogen, causing enteric infections. It is responsible for high mortality rate, especially in children, elderly, and immunocompromised people. To the best of our knowledge, no vaccine exists to curb this pathogen. Therefore, in current study, we aimed to identify potential vaccine candidates and design chimeric vaccine models against Escherichia albertii from the analysis of publicly available data of 95 strains, using a reverse vaccinology approach. Outer-membrane proteins (n = 4) were identified from core genome as vaccine candidates. Eventually, outer membrane Fimbrial usher (FimD) protein was selected as a promiscuous vaccine candidate and utilized to construct a potential vaccine model. It resulted in three epitopes, leading to the design of twelve vaccine constructs. Amongst these, V6 construct was found to be highly immunogenic, non-toxic, non-allergenic, antigenic, and most stable. This was utilized for molecular docking and simulation studies against six HLA and two TLR complexes. This construct can therefore be used for pan-therapy against different strains of E. albertii and needs to be tested in vitro and in vivo.

Antimicrobial Properties of Chitosan and Chitosan Derivatives in the Treatment of Enteric Infections

Antibiotics played an important role in controlling the development of enteric infection. However, the emergence of antibiotic resistance and gut dysbiosis led to a growing interest in the use of natural antimicrobial agents as alternatives for therapy and disinfection. Chitosan is a nontoxic natural antimicrobial polymer and is approved by GRAS (Generally Recognized as Safe by the United States Food and Drug Administration). Chitosan and chitosan derivatives can kill microbes by neutralizing negative charges on the microbial surface. Besides, chemical modifications give chitosan derivatives better water solubility and antimicrobial property. This review gives an overview of the preparation of chitosan, its derivatives, and the conjugates with other polymers and nanoparticles with better antimicrobial properties, explains the direct and indirect mechanisms of action of chitosan, and summarizes current treatment for enteric infections as well as the role of chitosan and chitosan derivatives in the antimicrobial agents in enteric infections. Finally, we suggested future directions for further research to improve the treatment of enteric infections and to develop more useful chitosan derivatives and conjugates.

UNUSUAL PRESENTATION OF REACTIVE ARTHRITIS AFTER SALMONELLA ENTERITIS IN A 6-YEAR-OLD BOY

ABSTRACT: Reactive arthritis, formerly called Reiter’s syndrome is extra-articular oligoarthropathy, which can be due to bacterial infection or genetic predisposition. The infections are either urogenital (chlamydia being most notorious) or gastrointestinal (e.g. salmonella, yersinia, etc.). The human leukocyte antigen (HLA-B27) antigen has been implicated as the most common predisposing factor. Reactive arthritis often involves the joints of the lower limb. Bacterial enteric infections are a potential threat in a Pediatric population that can be due to an acute illness or its sequelae. Reactive arthritis following outbreaks of enteric infections with Salmonella is uncommon in the pediatric population. We report a rare case of a 6 years old boy who came to ER with high-grade fever and severe pain in the right iliac fossa. Clinical diagnosis of appendicitis was made by the physicians on physical exam but after radio-pathological investigation like CBC, ESR, CRP, Blood culture, USG abdomen, CT abdomen, and MRI, diagnosis of reactive arthritis secondary to salmonella enteritis was made and the patient underwent right hip arthrotomy after which he was discharged. Thus, imaging played a pivotal role in the right diagnosis of a patient with proper management guidelines. This also showed that salmonella enteritis can present atypically mimicking septic arthritis or acute appendicitis. Reactive arthritis after salmonella infection is a very rare and one of its kind case reported in Pakistan.

Prevalence of Diarrheagenic E. Coli Among Hospitalized Children in a Clinical Centre

Introduction. Escherichia coli is a common cause of acute diarrhea mainly in young children and, less frequently, in elderly or immunosuppressed patients. Many types of E. coli are part of the normal enteric flora, but can cause urinary tract or nervous system infections. Objective. To study the prevalence of the main types and serogroups of diarrheagenic E. coli among hospitalized children with enteric infections. Material and methods. Over a period of 5 years, 1,160 hospitalized children with acute diarrhea syndrome were studied. Fecal samples underwent culturing, biochemical and phenotypic identification. Results. Among the studied patients, 112/1,160 children (9.7%) had diarrhea caused by E. coli, and only 4 of the isolates were lactose-negative. The most common was diarrhea caused by ETEC – 65/112 (58.0%), followed by EPEC – 38/112 (33.9%), and in third place – EHES 9/112 (8.0%). We did not isolate EIEC types. Depending on the group of E. coli, we observed some differences in the clinical presentation and specifics in the distribution of patients by age. Conclusion. The study shows that this causative agent is common among Bulgarian children with diarrhea. Unfortunately, in Bulgaria the microbiological network is still not able to adequately respond to the challenges of the extended serodiagnosis for detection of diarrheagenic E. coli, which is performed in Western Europe and North America.

Gut microbiome, enteric infections and child growth across a rural–urban gradient: protocol for the ECoMiD prospective cohort study

IntroductionThe functional consequences of the bacterial gut microbiome for child health are not well understood. Characteristics of the early child gut microbiome may influence the course of enteric infections, and enteric infections may change the composition of the gut microbiome, all of which may have long-term implications for child growth and development.Methods and analysisWe are conducting a community-based birth cohort study to examine interactions between gut microbiome conditions and enteric infections, and how environmental conditions affect the development of the gut microbiome. We will follow 360 newborns from 3 sites along a rural–urban gradient in northern coastal Ecuador, characterising enteric infections and gut microbial communities in the children every 3 to 6 months over their first 2 years of life. We will use longitudinal regression models to assess the correlation between environmental conditions and gut microbiome diversity and presence of specific taxa, controlling for factors that are known to be associated with the gut microbiome, such as diet. From 6 to 12 months of age, we will collect weekly stool samples to compare microbiome conditions in diarrhoea stools versus stools from healthy children prior to, during and after acute enteric infections, using principal-coordinate analysis and other multivariate statistical methods.Ethics and disseminationEthics approvals have been obtained from Emory University and the Universidad San Francisco de Quito institutional review boards. The findings will be disseminated through conference presentations and peer-reviewed journals.