Association between enteropathogens and malnutrition in children aged 6-23 mo in Bangladesh: a case-control study

Virulence-Related Genes and Coenteropathogens Associated with Clinical Outcomes of Enteropathogenic Escherichia coli Infections in Children from the Brazilian Semiarid Region: a Case-Control Study of Diarrhea

Enteropathogenic Escherichia coli (EPEC) is a major cause of diarrhea in children from developing countries and presents high genetic variability. We aimed to characterize the EPEC virulence-related gene (VRG) distribution and copathogens associated with diarrhea and nutrition-related outcomes in children from the low-income Brazilian semiarid region. A cross-sectional case-control study of diarrhea was conducted in 1,191 children aged 2 to 36 months from the northeast region of Brazil. Stool samples were collected and clinical, epidemiological, and anthropometric data were identified from each child. A broad molecular evaluation of enteropathogens was performed, and EPEC-positive samples were further investigated for 18 VRGs using five multiplex PCRs. EPEC was detected in 28.2% of the study population, with similar proportions among cases and controls. Typical EPEC (tEPEC) infections were more often associated with diarrhea than atypical EPEC (aEPEC) infections, while aEPEC infections presented a higher prevalence. The VRG ler, a negative regulator of the locus of enterocyte effacement, was associated with the absence of diarrhea in aEPEC-positive children; espB, a major component of the type 3 secretion system, was associated with diarrhea in tEPEC-positive children; the presence of procolonization VRGs-the combination of cesT positivity, espP negativity, and the presence of the map gene-was associated with undernutrition; and Campylobacter spp., norovirus, and enteroaggregative E. coli (EAEC) coinfections were associated with increased clinical severity in EPEC-infected children. These data identified tEPEC strains associated with diarrhea and specific VRGs of EPEC (ler, espB, cesT, and map genes) and Campylobacter spp., norovirus, and EAEC to be major contributors to diarrhea and undernutrition in children from a low-income Brazilian region.

Virulence-related genes are associated with clinical and nutritional outcomes of Shigella/Enteroinvasive Escherichia coli pathotype infection in children from Brazilian semiarid region: A community case-control study

Shigella/Enteroinvasive Escherichia coli (EIEC) pathotype is a major enteropathogen associated with diarrhea and malnutrition in children from developing countries. This study aimed to correlate Shigella/EIEC virulence-related genes (VRGs) with clinical symptoms, nutritional status and coenteropathogens in children from the Brazilian semiarid region. We designed a case-control study of community diarrhea in six cities of the Brazil semiarid region with 1200 children aging 2-36 months. Standardized questionnaire was applied for collecting sociodemographic, nutritional status and clinical information of the children. DNA samples were extracted from stools and diagnosed for Shigella/EIEC using PCR-based approaches. Positive samples were tested for 28 VRGs using four multiplex PCRs. Intestinal inflammation was determined by measuring fecal myeloperoxidase (MPO). Shigella/EIEC pathotype was detected in 5% of the children and was significantly associated with diarrhea. The genes sen (encoding Shigella enterotoxin 2), ipgB2, ipgB1 (both encoding type 3 secretion system-T3SS effectors that modulate actin filament), and ospF (encoding a T3SS effector involved in suppression of host responses) were further associated with diarrhea in Shigella/EIEC positive children. Among children presenting diarrhea, virA gene (encoding a T3SS effector that promotes microtubule destabilization) was associated with fever, while virB (encoding a major transcriptional activator) was associated with low height-for-age z-score. In addition, these VRGs were associated with increased fecal MPO, and coinfection with Salmonella spp. was associated with increased abdominal pain. These data reinforce the impact of Shigella/EIEC on diarrhea in children from Brazilian semiarid region and highlighted the contributions of specific virulence genes for its pathobiology.

Disentangling Microbial Mediators of Malnutrition: Modeling Environmental Enteric Dysfunction

Environmental enteric dysfunction (EED) (also referred to as environmental enteropathy) is a subclinical chronic intestinal disorder that is an emerging contributor to early childhood malnutrition. EED is common in resource-limited settings, and is postulated to consist of small intestinal injury, dysfunctional nutrient absorption, and chronic inflammation that results in impaired early child growth attainment. Although there is emerging interest in the hypothetical potential for chemical toxins in the environmental exposome to contribute to EED, the propensity of published data, and hence the focus of this review, implicates a critical role of environmental microbes. Early childhood malnutrition and EED are most prevalent in resource-limited settings where food is limited, and inadequate access to clean water and sanitation results in frequent gastrointestinal pathogen exposures. Even as overt diarrhea rates in these settings decline, silent enteric infections and faltering growth persist. Furthermore, beyond restricted physical growth, EED and/or enteric pathogens also associate with impaired oral vaccine responses, impaired cognitive development, and may even accelerate metabolic syndrome and its cardiovascular consequences. As these potentially costly long-term consequences of early childhood enteric infections increasingly are appreciated, novel therapeutic strategies that reverse damage resulting from nutritional deficiencies and microbial insults in the developing small intestine are needed. Given the inherent limitations in investigating how specific intestinal pathogens directly injure the small intestine in children, animal models provide an affordable and controlled opportunity to elucidate causal sequelae of specific enteric infections, to differentiate consequences of defined nutrient deprivation alone from co-incident enteropathogen insults, and to correlate the resulting gut pathologies with their functional impact during vulnerable early life windows.

Pathogens, microbiome and the host: emergence of the ecological Koch's postulates

Even though tremendous progress has been made in the last decades to elucidate the mechanisms of intestinal homeostasis, dysbiosis and disease, we are only at the beginning of understanding the complexity of the gut ecosystem and the underlying interaction networks. We are also only starting to unravel the mechanisms that pathogens have evolved to overcome the barriers imposed by the microbiota and host to exploit the system to their own benefit. Recent work in these domains clearly indicates that the 'traditional Koch's postulates', which state that a given pathogen leads to a distinct disease, are not valid for all 'infectious' diseases, but that a more complete and complex interpretation of Koch's postulates is needed in order to understand and explain them. This review summarises the current understanding of what defines a healthy gut ecosystem and highlights recent progress in uncovering the interplay between the host, its microbiota and invading intestinal pathogens. Based on these recent findings, we propose a new interpretation of Koch's postulates that we term 'ecological Koch's postulates'.

New Insights into the Pathogenesis and Treatment of Malnutrition

The volume of research into the pathogenesis and treatment of malnutrition has increased markedly over the past ten years, providing mechanistic insights that can be leveraged into more effective treatment options. These discoveries have been driven by several landmark studies employing metabolomics, metagenomics, and new preclinical models. This review highlights some of the most important recent findings, focusing in particular on the emerging roles of prenatal and perinatal factors, protein deficiency, impaired gut barrier function, immune deficiency, and the intestinal microbiome.

Campylobacter jejuni virulence genes and immune-inflammatory biomarkers association with growth impairment in children from Northeastern Brazil

Campylobacter spp. have been associated with anthropometric Z-score decrements, but the role of specific virulence genes associated with these outcomes has not been explored. This study aimed to investigate whether specific Campylobacter jejuni virulence-related gene and immune-inflammatory biomarkers are associated with malnutrition in children from Northeastern Brazil. A case-control study was performed in Fortaleza, Brazil. Children aging 6-24 months were characterized as malnourished (cases) if weight-for-age Z-score (WAZ) = 2 and as nourished (controls) if WAZ ≥ 1. DNA samples were extracted from stools and screened for C. jejuni/coli by real-time PCR. A subsequent C. jejuni-specific PCR was employed and positive samples were evaluated for 18 C. jejuni virulence genes by using four multiplex PCRs. C. jejuni was detected in 9.71% (33/340) of the children's samples, being 63.63% (21/33) from nourished and 37.37% (12/33) from malnourished children. The cadF, iamA, cheW, and sodB genes were the most frequent genes (100%, 90.9%, 87.9%, and 75.8%, respectively), while some others (ceuE, jlpA, pldA, and pVir) showed low rates (all below 6%). Malnourished children were significantly associated with infection with C. jejuni strains lacking cdtB gene (active subunit of cytolethal distending toxin) and harboring flgE gene (flagellar hook protein). These strains were also associated with children presenting increased serum SAA and sCD-14, but decreased IgG anti-LPS. These data reinforce the impact of Campylobacter jejuni infection on children without diarrhea and highlight the contribution of a specific virulence gene profile, cdtB(-)flgE(+) and increased systemic response in malnutrition children.

Children living in the slums of Bangladesh face risks from unsafe food and water and stunted growth is common

AIM

This study investigated the microbial quality of food and water consumed by children in four slums in Dhaka, the capital of Bangladesh, together with the associated risk factors.

METHODS

This cross-sectional study took place from December 2015 to May 2016 and focused on 360 children under the age of five. We recorded household food security, namely adequate food for a healthy life, socio-economic and nutritional status, hygiene and feeding practices. Food and water samples were analysed.

RESULTS

We found that 63% of the children were malnourished and 58% were stunted. Yeast and moulds were detected in 86% of the food samples and coliforms in 73%. All the water samples were contaminated with faecal coliforms, yeasts and moulds and Staphylococcus. Food insecurity affected 83% of households. Children were twice as likely to be malnourished if they were born with a perceived low birthweight or their mothers did not wash their hands with soap after cleaning the child's bottom following defecation. Exclusively breastfed children were less likely to develop malnutrition.

CONCLUSION

Children from the Dhaka slums were frequently stunted and malnourished and contaminated food and water was common. Integrated efforts are essential to create public awareness about hygiene.

What Is a Host? Attributes of Individual Susceptibility

In every epidemic some individuals become sick and some may die, whereas others recover from illness and still others show no signs or symptoms of disease. These differences highlight a fundamental question of microbial pathogenesis: why are some individuals susceptible to infectious diseases while others who acquire the same microbe remain well? For most of human history, the answer assumed the hand of providence. With the advent of the germ theory of disease, the focus on disease causality became the microbe, but this did not explain how there can be different outcomes of infection in different individuals with the same microbe. Here we examine the attributes of susceptibility in the context of the "damage-response framework" of microbial pathogenesis. We identify 11 attributes that, although not independent, are sufficiently distinct to be considered separately: microbiome, inoculum, sex, temperature, environment, age, chance, history, immunity, nutrition, and genetics. We use the first letter of each to create the mnemonic MISTEACHING, underscoring the need for caution in accepting dogma and attributing disease causality to any single factor. For both populations and individuals, variations in the attributes that assemble into MISTEACHING can create an enormity of combinations that can in turn translate into different outcomes of host-microbe encounters. Combinatorial diversity among the 11 attributes makes identifying "signatures" of susceptibility possible. However, with their inevitable uncertainties and propensity to change, there may still be a low likelihood for prediction with regard to individual host-microbe interactions, although probabilistic prediction may be possible.

Causes of impaired oral vaccine efficacy in developing countries

Oral vaccines are less immunogenic when given to infants in low-income compared with high-income countries, limiting their potential public health impact. Here, we review factors that might contribute to this phenomenon, including transplacental antibodies, breastfeeding, histo blood group antigens, enteric pathogens, malnutrition, microbiota dysbiosis and environmental enteropathy. We highlight several clear risk factors for vaccine failure, such as the inhibitory effect of enteroviruses on oral poliovirus vaccine. We also highlight the ambiguous and at times contradictory nature of the available evidence, which undoubtedly reflects the complex and interconnected nature of the factors involved. Mechanisms responsible for diminished immunogenicity may be specific to each oral vaccine. Interventions aiming to improve vaccine performance may need to reflect the diversity of these mechanisms.

Enteric Infections in Young Children are Associated with Environmental Enteropathy and Impaired Growth

OBJECTIVE

To investigate the relationship between faecal contamination in child play spaces, enteric infections, environmental enteropathy (EE) and impaired growth among young children.

METHODS

A prospective cohort study was conducted of 203 children 6-30 months of age in rural Bangladesh. Stool samples were analysed by quantitative PCR for Shigella, Enterotoxigenic Escherichia coli (ETEC), Campylobacter jejuni, Giardia intestinalis and Cryptosporidium spp. Four faecal markers of intestinal inflammation were also measured: alpha-1-antitrypsin, myeloperoxidase, neopterin and calprotectin. Child growth was measured at baseline and 9 months after enrolment. E. coli was measured in soil in child play spaces.

RESULTS

Forty-seven percent of study children had three or more enteric pathogens in their stool. Thirty five percent (71/203) of children had Shigella, 30% (61/203) had ETEC, 73% (148/203) had C. jejuni, 79% (160/203) had Giardia intestinalis and none had Cryptosporidium. Children with ETEC had significantly higher calprotectin concentrations (Coefficient: 1.35, 95% Confidence Interval [CI]: 1.005, 1.82). Children with Shigella had a significantly higher odds of being stunted at our 9-month follow-up (OR: 2.01, 95% CI: 1.02, 3.93). Children with Giardia intestinalis had significantly higher E.coli counts in the soil collected from their play spaces (OR: 1.23, 95% CI: 1.02, 1.48).

CONCLUSION

Enteric infections were significantly associated with EE and impaired growth in rural Bangladesh. These findings provide further evidence to support the hypothesis that contaminated soil in child play spaces can lead to enteric infections, many of which are likely subclinical, resulting in EE and impaired growth in young children.

Epidemiology of enteroaggregative Escherichia coli infections and associated outcomes in the MAL-ED birth cohort

Background

Enteroaggregative E. coli (EAEC) have been associated with mildly inflammatory diarrhea in outbreaks and in travelers and have been increasingly recognized as enteric pathogens in young children with and without overt diarrhea. We examined the risk factors for EAEC infections and their associations with environmental enteropathy biomarkers and growth outcomes over the first two years of life in eight low-resource settings of the MAL-ED study.

Methods

EAEC infections were detected by PCR gene probes for aatA and aaiC virulence traits in 27,094 non-diarrheal surveillance stools and 7,692 diarrheal stools from 2,092 children in the MAL-ED birth cohort. We identified risk factors for EAEC and estimated the associations of EAEC with diarrhea, enteropathy biomarker concentrations, and both short-term (one to three months) and long-term (to two years of age) growth.

Results

Overall, 9,581 samples (27.5%) were positive for EAEC, and almost all children had at least one detection (94.8%) by two years of age. Exclusive breastfeeding, higher enrollment weight, and macrolide use within the preceding 15 days were protective. Although not associated with diarrhea, EAEC infections were weakly associated with biomarkers of intestinal inflammation and more strongly with reduced length at two years of age (LAZ difference associated with high frequency of EAEC detections: -0.30, 95% CI: -0.44, -0.16).

Conclusions

Asymptomatic EAEC infections were common early in life and were associated with linear growth shortfalls. Associations with intestinal inflammation were small in magnitude, but suggest a pathway for the growth impact. Increasing the duration of exclusive breastfeeding may help prevent these potentially inflammatory infections and reduce the long-term impact of early exposure to EAEC.

Enteroaggregative E. coli (EAEC) are pathogens that infect the intestine and can cause diarrhea. They are also commonly identified among young children in low-resource settings, who can carry the pathogen without symptomatic diarrhea. We examined the risk factors for EAEC infections and their associations with child health outcomes over the first two years of life in eight low-resource settings of the MAL-ED study. EAEC infections were detected using molecular methods in more than 30,000 stools collected from 2,092 children in the MAL-ED study. We identified risk factors for EAEC and estimated the associations of EAEC with diarrhea, markers of intestinal health, and child growth. Almost all children were infected with EAEC at least once by two years of age. Exclusive breastfeeding, higher enrollment weight, and recent macrolide antibiotic use were protective against these infections. Although not associated with diarrhea in these children, EAEC infections were associated with intestinal inflammation and reduced length at two years of age. EAEC may impact child development, even in the absence of diarrhea, by causing intestinal inflammation and impairing child growth.