Giardia hinders growth by disrupting nutrient metabolism independent of inflammatory enteropathy

Giardia lamblia (Giardia) is among the most common intestinal pathogens in children in low- and middle-income countries (LMICs). Although Giardia associates with early-life linear growth restriction, mechanistic explanations for Giardia-associated growth impairments remain elusive. Unlike other intestinal pathogens associated with constrained linear growth that cause intestinal or systemic inflammation or both, Giardia seldom associates with chronic inflammation in these children. Here we leverage the MAL-ED longitudinal birth cohort and a model of Giardia mono-association in gnotobiotic and immunodeficient mice to propose an alternative pathogenesis of this parasite. In children, Giardia results in linear growth deficits and gut permeability that are dose-dependent and independent of intestinal markers of inflammation. The estimates of these findings vary between children in different MAL-ED sites. In a representative site, where Giardia associates with growth restriction, infected children demonstrate broad amino acid deficiencies, and overproduction of specific phenolic acids, byproducts of intestinal bacterial amino acid metabolism. Gnotobiotic mice require specific nutritional and environmental conditions to recapitulate these findings, and immunodeficient mice confirm a pathway independent of chronic T/B cell inflammation. Taken together, we propose a new paradigm that Giardia-mediated growth faltering is contingent upon a convergence of this intestinal protozoa with nutritional and intestinal bacterial factors.

Beyond research: improved perinatal care through scale-up of a Moyo fetal heart rate monitor coupled with simulation training in northern Tanzania for helping babies breathe

BACKGROUND

The purpose of this project was to improve perinatal survival by introducing Moyo Fetal Heart Rate (FHR) Monitor coupled with neonatal resuscitation simulation training.

METHODS

The implementation was done at three district hospitals. We assessed health care workers' (HCW's) skills and perinatal death trends during implementation. Baseline data were collected from the hospitals before implementation. Newborn resuscitation (NR) skills were assessed before and after simulation training. Assessment of perinatal outcomes was done over 2 years of implementation. We used descriptive analysis; a t-test (paired and independent two-sample) and a one-way Anova test to report the findings.

RESULTS

A total of 107 HCW's were trained on FHR monitoring using Moyo and NR knowledge and skills using NeoNatalie simulators. The knowledge increased post-training by 13.6% (p <  0.001). Skills score was increased by 25.5 and 38.2% for OSCE A and B respectively (p <  0.001). The overall fresh stillbirths rate dropped from 9 to 5 deaths per 1000 total births and early neonatal deaths at 7 days from 5 to 3 (p <  0.05) deaths per 1000 live births over 2 years of implementation.

CONCLUSION

There was a significant improvement of newborn resuscitation skills among HCW's and neonatal survival at 2 years. Newborn resuscitation training coupling with Moyo FHR monitor has shown potential for improving perinatal survival. However, further evaluation is needed to explore the full potential of the package.

Associations of Enteric Protein Loss, Vaccine Response, Micronutrient Deficiency, and Maternal Depressive Symptoms with Deviance in Childhood Linear Growth: Results from a Multicountry Birth Cohort Study

We identified the determinants of positive (children who had a birth weight < 2.5 kg and/or maternal height < 145 cm but were nonstunted at 24 months of age) and negative (children who had a birth weight ≥ 2.5 kg and maternal height ≥ 145 cm but were stunted at 24 months of age) deviance in childhood linear growth. We found that socioeconomic status (β = 1.54, P < 0.01), serum retinol (β = 0.05, P < 0.01), hemoglobin (β = 0.36, P < 0.01), length-for-age Z-score (LAZ) at birth (β = 0.47, P < 0.01), and tetanus vaccine titer (β = 0.182, P < 0.05) were positively and maternal depressive symptom (β = -0.05, P < 0.01), serum ferritin (β = -0.03, P < 0.01), male sex (β = -1.08, P < 0.01), and α1-antitrypsin (β = -0.81, P < 0.01) were negatively associated with positive deviance. Further, diarrhea episodes (β = 0.02, P < 0.01), male sex (β = 0.72, P < 0.01), and α1-antitrypsin (β = 0.67, P < 0.01) were positively and hemoglobin (β= -0.28, P < 0.01), soluble transferrin receptor level (β = -0.15, P < 0.01), and LAZ score at birth (β = -0.90, P < 0.01) were negatively associated with negative deviance. To summarize, enteric protein loss, micronutrient deficiency, vaccine responses and maternal depressive symptoms were associated with linear growth deviance in early childhood. In such a background, public health approaches aimed at reducing the risk of intestinal inflammation and altered gut permeability could prove fruitful in ensuring desired linear growth in children. In addition, maternal mental health issue should also be considered, especially for promoting better nutritional status in children in the context of linear growth deviance.

Introducing a drift and diffusion framework for childhood growth research

Background: Growth trajectories are highly variable between children, making epidemiological analyses challenging both to the identification of malnutrition interventions at the population level and also risk assessment at individual level. We introduce stochastic differential equation (SDE) models into child growth research. SDEs describe flexible dynamic processes comprising: drift - gradual smooth changes - such as physiology or gut microbiome, and diffusion - sudden perturbations, such as illness or infection. Methods: We present a case study applying SDE models to child growth trajectory data from the Haydom, Tanzania and Venda, South Africa sites within the MAL-ED cohort. These data comprise n=460 children aged 0-24 months. A comparison with classical curve fitting (linear mixed models) is also presented. Results: The SDE models offered a wide range of new flexible shapes and parameterizations compared to classical additive models, with performance as good or better than standard approaches. The predictions from the SDE models suggest distinct longitudinal clusters that form distinct 'streams' hidden by the large between-child variability. Conclusions: Using SDE models to predict future growth trajectories revealed new insights in the observed data, where trajectories appear to cluster together in bands, which may have a future risk assessment application. SDEs offer an attractive approach for child growth modelling and potentially offer new insights.

Introducing a drift and diffusion framework for childhood growth research

Background: Growth trajectories are highly variable between children, making epidemiological analyses challenging both to the identification of malnutrition interventions at the population level and also risk assessment at individual level. We introduce stochastic differential equation (SDE) models into child growth research. SDEs describe flexible dynamic processes comprising: drift - gradual smooth changes - such as physiology or gut microbiome, and diffusion - sudden perturbations, such as illness or infection. Methods: We present a case study applying SDE models to child growth trajectory data from the Haydom, Tanzania and Venda, South Africa sites within the MAL-ED cohort. These data comprise n=460 children aged 0-24 months. A comparison with classical curve fitting (linear mixed models) is also presented. Results: The SDE models offered a wide range of new flexible shapes and parameterizations compared to classical additive models, with performance as good or better than standard approaches. The predictions from the SDE models suggest distinct longitudinal clusters that form distinct 'streams' hidden by the large between-child variability. Conclusions: Using SDE models to predict future growth trajectories revealed new insights in the observed data, where trajectories appear to cluster together in bands, which may have a future risk assessment application. SDEs offer an attractive approach for child growth modelling and potentially offer new insights.

Metabolic maturation in the first 2 years of life in resource-constrained settings and its association with postnatal growths

Malnutrition continues to affect the growth and development of millions of children worldwide, and chronic undernutrition has proven to be largely refractory to interventions. Improved understanding of metabolic development in infancy and how it differs in growth-constrained children may provide insights to inform more timely, targeted, and effective interventions. Here, the metabolome of healthy infants was compared to that of growth-constrained infants from three continents over the first 2 years of life to identify metabolic signatures of aging. Predictive models demonstrated that growth-constrained children lag in their metabolic maturity relative to their healthier peers and that metabolic maturity can predict growth 6 months into the future. Our results provide a metabolic framework from which future nutritional programs may be more precisely constructed and evaluated.

Effects of Child and Maternal Histo-Blood Group Antigen Status on Symptomatic and Asymptomatic Enteric Infections in Early Childhood

Background

Histo-blood group antigens (HBGAs) such as fucosyltransferase (FUT)2 and 3 may act as innate host factors that differentially influence susceptibility of individuals and their offspring to pediatric enteric infections.

Methods

In 3 community-based birth cohorts, FUT2 and FUT3 statuses were ascertained for mother-child dyads. Quantitative polymerase chain reaction panels tested 3663 diarrheal and 18 148 asymptomatic stool samples for 29 enteropathogens. Cumulative diarrhea and infection incidence were compared by child (n = 520) and mothers’ (n = 519) HBGA status and hazard ratios (HRs) derived for all-cause diarrhea and specific enteropathogens.

Results

Children of secretor (FUT2 positive) mothers had a 38% increased adjusted risk of all-cause diarrhea (HR = 1.38; 95% confidence interval (CI), 1.15–1.66) and significantly reduced time to first diarrheal episode. Child FUT2 and FUT3 positivity reduced the risk for all-cause diarrhea by 29% (HR = 0.81; 95% CI, 0.71–0.93) and 27% (HR = 0.83; 95% CI, 0.74–0.92), respectively. Strong associations between HBGAs and pathogen-specific infection and diarrhea were observed, particularly for noroviruses, rotaviruses, enterotoxigenic Escherichia coli, and Campylobacter jejuni/coli.

Conclusions

Histo-blood group antigens affect incidence of all-cause diarrhea and enteric infections at magnitudes comparable to many common disease control interventions. Studies measuring impacts of interventions on childhood enteric disease should account for both child and mothers’ HBGA status.

Longitudinal Assessment of Antibiotic Resistance in Fecal Escherichia coli in Tanzanian Children

Antibiotic-resistant bacterial infections are a major public health problem, and children in low-resource settings represent a particularly high-risk group. Few data are available on the dynamics of and risk factors for gastrointestinal carriage of antibiotic-resistant bacteria in these vulnerable populations. In this study, we described the antibiotic susceptibility profiles of Escherichia coli isolated from stool specimens collected from children aged 6 to 60 months enrolled in a birth cohort study in Haydom, Tanzania. We estimated the association between sociodemographic risk factors, child illnesses, and antibiotic exposure and E. coli drug resistance. Carriage of antibiotic-resistant E. coli was common starting early in life and did not clearly increase with age. The majority of isolates were resistant to ampicillin (749/837; 89.5%), cefazolin (742/837; 88.6%), and cotrimoxazole (721/837; 86.1%). Resistance to amoxicillin/clavulanate (361/836; 43.2%), ampicillin/sulbactam (178/819; 21.7%), nalidixic acid (131/831; 15.8%), and azithromycin (115/837; 13.7%) was also seen. Only 1.8% (15/837) of the pooled E. coli isolates met the criteria for extended-spectrum beta-lactamase production. High antibiotic use (0.26 additional resistant antibiotic classes; 95% CI: 0.05, 0.47) and high income (0.28 additional resistant antibiotic classes; 95% CI: 0.06, 0.50) were associated with the carriage of antibiotic-resistant E. coli, whereas hospital birth, crowding in the home, improved drinking water and sanitation, and common childhood illnesses were not. In this setting, the carriage of antibiotic-resistant E. coli was common. Other than recent antibiotic exposure and high income, individual risk factors for the acquisition and carriage of resistance could not be identified, suggesting that population-level interventions are needed.

Pathogen-Specific Impacts of the 2011-2012 La Niña-Associated Floods on Enteric Infections in the MAL-ED Peru Cohort: A Comparative Interrupted Time Series Analysis

Extreme floods pose multiple direct and indirect health risks. These risks include contamination of water, food, and the environment, often causing outbreaks of diarrheal disease. Evidence regarding the effects of flooding on individual diarrhea-causing pathogens is limited, but is urgently needed in order to plan and implement interventions and prioritize resources before climate-related disasters strike. This study applied a causal inference approach to data from a multisite study that deployed broadly inclusive diagnostics for numerous high-burden common enteropathogens. Relative risks (RRs) of infection with each pathogen during a flooding disaster that occurred at one of the sites-Loreto, Peru-were calculated from generalized linear models using a comparative interrupted time series framework with the other sites as a comparison group and adjusting for background seasonality. During the early period of the flood, increased risk of heat-stable enterotoxigenic E. coli (ST-ETEC) was identified (RR = 1.73 [1.10, 2.71]) along with a decreased risk of enteric adenovirus (RR = 0.36 [0.23, 0.58]). During the later period of the flood, sharp increases in the risk of rotavirus (RR = 5.30 [2.70, 10.40]) and sapovirus (RR = 2.47 [1.79, 3.41]) were observed, in addition to increases in transmission of Shigella spp. (RR = 2.86 [1.81, 4.52]) and Campylobacter spp. (RR = 1.41 (1.01, 1.07). Genotype-specific exploratory analysis reveals that the rise in rotavirus transmission during the flood was likely due to the introduction of a locally atypical, non-vaccine (G2P[4]) strain of the virus. Policy-makers should target interventions towards these pathogens-including vaccines as they become available-in settings where vulnerability to flooding is high as part of disaster preparedness strategies, while investments in radical, transformative, community-wide, and locally-tailored water and sanitation interventions are also needed.

Epidemiology and Risk Factors for Cryptosporidiosis in Children From 8 Low-income Sites: Results From the MAL-ED Study

Background

Cryptosporidium species are enteric protozoa that cause significant morbidity and mortality in children worldwide. We characterized the epidemiology of Cryptosporidium in children from 8 resource-limited sites in Africa, Asia, and South America.

Methods

Children were enrolled within 17 days of birth and followed twice weekly for 24 months. Diarrheal and monthly surveillance stool samples were tested for Cryptosporidium by enzyme-linked immunosorbent assay. Socioeconomic data were collected by survey, and anthropometry was measured monthly.

Results

Sixty-five percent (962/1486) of children had a Cryptosporidium infection and 54% (802/1486) had at least 1 Cryptosporidium-associated diarrheal episode. Cryptosporidium diarrhea was more likely to be associated with dehydration (16.5% vs 8.3%, P < .01). Rates of Cryptosporidium diarrhea were highest in the Peru (10.9%) and Pakistan (9.2%) sites. In multivariable regression analysis, overcrowding at home was a significant risk factor for infection in the Bangladesh site (odds ratio, 2.3 [95% confidence interval {CI}, 1.2-4.6]). Multiple linear regression demonstrated a decreased length-for-age z score at 24 months in Cryptosporidium-positive children in the India (β = -.26 [95% CI, -.51 to -.01]) and Bangladesh (β = -.20 [95% CI, -.44 to .05]) sites.

Conclusions

This multicountry cohort study confirmed the association of Cryptosporidium infection with stunting in 2 South Asian sites, highlighting the significance of cryptosporidiosis as a risk factor for poor growth. We observed that the rate, age of onset, and number of repeat infections varied per site; future interventions should be targeted per region to maximize success.

Use of earth observation-derived hydrometeorological variables to model and predict rotavirus infection (MAL-ED): a multisite cohort study

BACKGROUND

Climate change threatens to undermine recent progress in reducing global deaths from diarrhoeal disease in children. However, the scarcity of evidence about how individual environmental factors affect transmission of specific pathogens makes prediction of trends under different climate scenarios challenging. We aimed to model associations between daily estimates of a suite of hydrometeorological variables and rotavirus infection status ascertained through community-based surveillance.

METHODS

For this analysis of multisite cohort data, rotavirus infection status was ascertained through community-based surveillance of infants in the eight-site MAL-ED cohort study, and matched by date with earth observation estimates of nine hydrometeorological variables from the Global Land Data Assimilation System: daily total precipitation volume (mm), daily total surface runoff (mm), surface pressure (mbar), wind speed (m/s), relative humidity (%), soil moisture (%), solar radiation (W/m2), specific humidity (kg/kg), and average daily temperatures (°C). Lag relationships, independent effects, and interactions were characterised by use of modified Poisson models and compared with and without adjustment for seasonality and between-site variation. Final models were created with stepwise selection of main effects and interactions and their validity assessed by excluding each site in turn and calculating Tjur's Coefficients of Determination.

FINDINGS

All nine hydrometeorological variables were significantly associated with rotavirus infection after adjusting for seasonality and between-site variation over multiple consecutive or non-consecutive lags, showing complex, often non-linear associations that differed by symptom status and showed considerable mutual interaction. The final models explained 5·9% to 6·2% of the variability in rotavirus infection in the pooled data and their predictions explained between 0·0% and 14·1% of the variability at individual study sites.

INTERPRETATION

These results suggest that the effect of climate on rotavirus transmission was mediated by four independent mechanisms: waterborne dispersal, airborne dispersal, virus survival on soil and surfaces, and host factors. Earth observation data products available at a global scale and at subdaily resolution can be combined with longitudinal surveillance data to test hypotheses about routes and drivers of transmission but showed little potential for making predictions in this setting.

FUNDING

Bill & Melinda Gates Foundation; Foundation for the National Institutes of Health, National Institutes of Health, Fogarty International Center; Sherrilyn and Ken Fisher Center for Environmental Infectious Diseases, Johns Hopkins School of Medicine; and NASA's Group on Earth Observations Work Programme.

Genotypic antimicrobial resistance assays for use on E. coli isolates and stool specimens

Antimicrobial resistance (AMR) is an emerging public health problem and methods for surveillance are needed. We designed 85 sequence-specific PCR reactions to detect 79 genes or mutations associated with resistance across 10 major antimicrobial classes, with a focus on E. coli. The 85 qPCR assays demonstrated >99.9% concordance with sequencing. We evaluated the correlation between genotypic resistance markers and phenotypic susceptibility results on 239 E. coli isolates. Both sensitivity and specificity exceeded 90% for ampicillin, ceftriaxone, cefepime, imipenem, ciprofloxacin, azithromycin, gentamicin, amikacin, trimethoprim/sulfamethoxazole, tetracycline, and chloramphenicol phenotypic susceptibility results. We then evaluated the assays on direct stool specimens and observed a sensitivity of 97% ± 5 but, as expected, a lower specificity of 75% ± 31 versus the genotype of the E. coli cultured from stool. Finally, the assays were incorporated into a convenient TaqMan Array Card (TAC) format. These assays may be useful for tracking AMR in E. coli isolates or directly in stool for targeted testing of the fecal antibiotic resistome.

1206. Risk Factors of Antibiotic Resistance in E. coli Isolated from the MAL-ED Birth Cohort Study in Rural Tanzania

Background

The emergence and spread of antimicrobial resistance is a serious global public health crisis. Drug-resistant Gram-negative bacteria, like Escherichia coli, are particularly concerning given their significant morbidity and mortality. Despite the increasing prevalence of drug-resistant Gram-negative bacteria worldwide, there are significant knowledge gaps in low resource countries. We aimed to characterize the prevalence, phenotypes, and risk factors of drug-resistant E. coli carriage in children up to age 5 from stool collected in the Etiology, Risk Factors, and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development (MAL-ED) birth cohort study in rural Tanzania.

Methods

Two hundred sixty-two children were enrolled in the MAL-ED Tanzania site. We randomly selected 100 children who had E. coli specimens archived every 6 months through 60 months. Up to five lactose-fermenting colonies were selected from growth on MacConkey agar. Drug susceptibility testing of 18 antibiotics was performed by disk diffusion. CLSI interpretive criteria were used for determination of resistance. Generalized estimating equations were used to create a multivariate Poisson regression model for drug resistance risk factors.

Results

Eight hundred twenty-three E. coli specimens were available for testing. The highest rates of resistance were to ampicillin, cefazolin, and cotrimoxazole, respectively. No carbapenem resistance was found. 1.8% met criteria for extended-spectrum β-lactamase production based on combination disk testing. 696 (84.6%) specimens met criteria for multi-drug resistance (nonsusceptible to at least 1 drug in at least three drug categories). In terms of dynamic risk factors, there was no association between antibiotic use or episodes of diarrhea and antibiotic resistance. For static risk factors, there was an association between higher income and increased antibiotic resistance.

Conclusion

Antibiotic resistance carriage is an under recognized problem in this setting. Resistance rates at 6 months of age are higher than expected, with surprisingly little variance explained by individual-level risk factors for resistance in this community.

Disclosures

All authors: No reported disclosures.

Comparison of three dehydration scales showed that they were of limited or no value for assessing small children with acute diarrhoea

AIM

We explored the diagnostic accuracy of the clinical dehydration scale (CDS), the World Health Organization (WHO) scale and the Gorelick scale for assessing dehydration in children admitted to a Tanzanian referral hospital.

METHODS

This was a prospective, observational study, carried out from April 2015 to January 2017 on children aged one month to five years admitted to the hospital with acute diarrhoea lasting less than five days. Before rehydration therapy, each patient's weight was recorded and the degree of dehydration was assessed based on the three scales. The reference standard was the percentage weight change between admission and discharge. The main outcomes were the sensitivity, specificity and positive and negative likelihood ratios (LRs) of the scales.

RESULTS

Data from 124 eligible patients were available. The CDS showed limited value for ruling in cases with some dehydration (LR 1.9, 95% confidence interval 1.1-2.8), but was of no value in assessing no and moderate to severe dehydration. The WHO and Gorelick scales were of no value in evaluating any degree of dehydration.

CONCLUSION

The WHO and Gorelick dehydration scales were no use for assessing dehydration in small children, and the CDS was of limited use for predicting cases with some dehydration.

Multiplex real time PCR panels to identify fourteen colonization factors of enterotoxigenic Escherichia coli (ETEC)

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of childhood diarrhea in low income countries and in travelers to those areas. Inactivated enterotoxins and colonization factors (CFs) are leading vaccine candidates, therefore it is important to determine the prevailing CF types in different geographic locations and populations. Here we developed real time PCR (qPCR) assays for 14 colonization factors, including the common vaccine targets. These assays, along with three enterotoxin targets (STh, STp, and LT) were formulated into three 5-plex qPCR panels, and validated on 120 ETEC isolates and 74 E. coli colony pools. The overall sensitivity and specificity was 99% (199/202) and 99% (2497/2514), respectively, compared to the CF results obtained with conventional PCR. Amplicon sequencing of discrepant samples revealed that the qPCR was 100% accurate. qPCR panels were also performed on nucleic acid extracted from stool and compared to the results of the ETEC isolates or E. coli colony pools cultured from them. 95% (105/110) of the CF detections in the cultures were confirmed in the stool. Additionally, direct testing of stool yielded 30 more CF detections. Among 74 randomly selected E. coli colony pools with paired stool, at least one CF was detected in 63% (32/51) of the colony pools while at least one CF was detected in 78% (47/60) of the stool samples (P = NS). We conclude that these ETEC CF assays can be used on both cultures and stool samples to facilitate better understanding of CF distribution for ETEC epidemiology and vaccine development.

Pathogen-specific burdens of community diarrhoea in developing countries: a multisite birth cohort study (MAL-ED)

BACKGROUND

Most studies of the causes of diarrhoea in low-income and middle-income countries have looked at severe disease in people presenting for care, and there are few estimates of pathogen-specific diarrhoea burdens in the community.

METHODS

We undertook a birth cohort study with not only intensive community surveillance for diarrhoea but also routine collection of non-diarrhoeal stools from eight sites in South America, Africa, and Asia. We enrolled children within 17 days of birth, and diarrhoeal episodes (defined as maternal report of three or more loose stools in 24 h, or one loose stool with visible blood) were identified through twice-weekly home visits by fieldworkers over a follow-up period of 24 months. Non-diarrhoeal stool specimens were also collected for surveillance for months 1-12, 15, 18, 21, and 24. Stools were analysed for a broad range of enteropathogens using culture, enzyme immunoassay, and PCR. We used the adjusted attributable fraction (AF) to estimate pathogen-specific burdens of diarrhoea.

FINDINGS

Between November 26, 2009, and February 25, 2014, we tested 7318 diarrhoeal and 24 310 non-diarrhoeal stools collected from 2145 children aged 0-24 months. Pathogen detection was common in non-diarrhoeal stools but was higher with diarrhoea. Norovirus GII (AF 5·2%, 95% CI 3·0-7·1), rotavirus (4·8%, 4·5-5·0), Campylobacter spp (3·5%, 0·4-6·3), astrovirus (2·7%, 2·2-3·1), and Cryptosporidium spp (2·0%, 1·3-2·6) exhibited the highest attributable burdens of diarrhoea in the first year of life. The major pathogens associated with diarrhoea in the second year of life were Campylobacter spp (7·9%, 3·1-12·1), norovirus GII (5·4%, 2·1-7·8), rotavirus (4·9%, 4·4-5·2), astrovirus (4·2%, 3·5-4·7), and Shigella spp (4·0%, 3·6-4·3). Rotavirus had the highest AF for sites without rotavirus vaccination and the fifth highest AF for sites with the vaccination. There was substantial variation in pathogens according to geography, diarrhoea severity, and season. Bloody diarrhoea was primarily associated with Campylobacter spp and Shigella spp, fever and vomiting with rotavirus, and vomiting with norovirus GII.

INTERPRETATION

There was substantial heterogeneity in pathogen-specific burdens of diarrhoea, with important determinants including age, geography, season, rotavirus vaccine usage, and symptoms. These findings suggest that although single-pathogen strategies have an important role in the reduction of the burden of severe diarrhoeal disease, the effect of such interventions on total diarrhoeal incidence at the community level might be limited.

Association between stool enteropathogen quantity and disease in Tanzanian children using TaqMan array cards: a nested case-control study

Etiologic studies of diarrhea are limited by uneven diagnostic methods and frequent asymptomatic detection of enteropathogens. Polymerase chain reaction-based stool pathogen quantification may help distinguish clinically significant infections. We performed a nested case-control study of diarrhea in infants from a community-based birth cohort in Tanzania. We tested 71 diarrheal samples and pre-diarrheal matched controls with a laboratory-developed TaqMan Array Card for 19 enteropathogens. With qualitative detection, no pathogens were significantly associated with diarrhea. When pathogen quantity was considered, rotavirus (odds ratio [OR] = 2.70 per log10 increase, P < 0.001), astrovirus (OR = 1.49, P = 0.01), and Shigella/enteroinvasive Escherichia coli (OR = 1.47, P = 0.04) were associated with diarrhea. Enterotoxigenic E. coli (0.15 SD decline in length-for-age z score after 3 months per log10 increase, P < 0.001) and Campylobacter jejuni/C. coli (0.11 SD decline, P = 0.003) in pre-diarrheal stools were associated with poor linear growth. Quantitative analysis can help refine the association between enteropathogens and disease in endemic settings.