Defining the causes of diarrhea: novel approaches

Etiology and risk factors for diarrheal disease amongst rural and peri-urban populations in Cambodia, 2012-2018

Diarrheal diseases are a leading cause of mortality and morbidity, disproportionally affecting persons residing in low and middle-income countries. Accessing high-resolution surveillance data to understand community-level etiology and risk remains challenging, particularly in remote and resource limited populations. A multi-year prospective cohort study was conducted in two rural and two peri-urban villages in Cambodia from 2012 to 2018 to describe the epidemiology and etiology of acute diarrheal diseases within the population. Suspected diarrheal episodes among participants were self-reported or detected via routine weekly household visits. Fresh stool and fecal swabs were tested, and acute-illness and follow-up participant questionnaires collected. Of 5027 enrolled participants, 1450 (28.8%) reported at least one diarrheal incident. A total of 4266 individual diarrhea case events were recorded. Diarrhea incidence rate was calculated to be 281.5 persons per 1000 population per year, with an event rate of 664.3 individual diarrhea events occurring per 1000 population per year. Pathogenic Escherichia coli, Aeromonas spp., and Plesiomonas shigelloides were the most prevalent bacterial infections identified. Hookworm and Strongyloides stercoralis were the predominant helminth species, while Blastocystis hominis and Giardia lamblia were the predominant protozoan species found. Norovirus genotype 2 was the predominant virus identified. Mixed infections of two or more pathogens were detected in 36.2% of positive cases. Risk analyses identified unemployed status increased diarrhea risk by 63% (HR = 1.63 [95% CI 1.46, 1.83]). Individuals without access to protected water sources or sanitation facilities were 59% (HR = 1.59 [95% CI 1.49, 1.69]) and 19% (HR = 1.19 [95% CI 1.12, 1.28]) greater risk of contracting diarrhea, respectively. Patient-level surveillance data captured in this long-term study has generated a unique spatiotemporal profile of diarrheal disease in Cambodia. Understanding etiologies, together with associated epidemiological and community-level risk, provides valuable public health insight to support effective planning and delivery of appropriate local population-targeted interventions.

The burden of diarrhea, etiologies, and risk factors in India from 1990 to 2019: evidence from the global burden of disease study

Background

This study aims to measure the burden of diarrhea in India and analyze the trend of mortality associated with it for the past 30 years. We also intend to find the prevailing etiology and risk factors associated with diarrheal mortality in India.

Methods

The study has used the latest round of Global Burden of Disease (GBD) study-2019. GBD data is available across age groups and gender-wise over the period from 1990 to 2019. The study has identified 13 etiologies for the cause of diarrhea deaths and 20 risk factors to analyze the burden of disease.

Results

Our study shows, childhood diarrhea has declined over the years significantly, yet contributes to a larger share of DALYs associated with the disease. Among all the death cases of Diarrhea, in 2019, the most prevalent disease-causing pathogen is found to be Campylobacter. But Adenovirus is the major contributor to childhood diarrheal deaths. Though the burden of diarrhea is declining over the period, still there is a need to progress the interventions to prevent and control diarrhea rapidly to avoid the huge number of deaths and disabilities experienced in India.

Conclusions

Consumption of safe and clean water, proper sanitation facility in every household, required nutrition intake by mother and child, safe breastfeeding and stool disposal practices and careful case management, rotavirus vaccination are some of the effective interventions to be implemented all over the country. Further, evidence-based policies should be made and implemented to sustain diarrhea prevention programs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12515-3.

Evaluation of the BioFire Gastrointestinal Panel to Detect Diarrheal Pathogens in Pediatric Patients

Infectious diarrhea is a global pediatric health concern; therefore, rapid and accurate detection of enteropathogens is vital. We evaluated the BioFire^® FilmArray^® Gastrointestinal (GI) Panel with that of comparator laboratory tests. Stool samples of pediatric patients with diarrhea were prospectively collected and tested. As a comparator method for bacteria, culture, conventional PCR for diarrheagenic E. coli, and Allplex GI-Bacteria(I) Assay were tested. For discrepancy analysis, BD MAX Enteric Bacterial Panel was used. As a comparator method for virus, BD MAX Enteric Virus Panel and immunochromatography was used and Allplex GI-Virus Assay was used for discrepancy analysis. The “true positive” was defined as culture-positive and/or positive results from more than two molecular tests. Of the 184 stool samples tested, 93 (50.5%) were true positive for 128 pathogens, and 31 (16.9%) were positive for multiple pathogens. The BioFire GI Panel detected 123 pathogens in 90 of samples. The BioFire GI Panel demonstrated a sensitivity of 100% for 12 targets and a specificity of >95% for 16 targets. The overall positive rate and multiple pathogen rate among patients in the group without underlying diseases were significantly higher than those in the group with hematologic disease (57.0% vs. 28.6% (p = 0.001) and 20.4% vs. 4.8% (p = 0.02), respectively). The BioFire GI Panel provides comprehensive results within 2 h and may be useful for the rapid identification of enteropathogens.

Evaluation of Water, Sanitation, and Hygiene, Behavioral Aspects, Household State for the Diarrhea Prevalence among Students in the Valley of Sinabung Volcano, North Sumatera, Indonesia

Diarrhea stands as a result of the inter-variable relationships, including behavior, environmental aspect, and household states. The study aimed to conduct an epidemiologic survey of diarrhea prevalence and several existing risk factors of diarrhea. A community-based surveillance and in-depth interview were conducted following the JMP ladder service for WASH and government regulation and it enrolled 135 children of a public primary school, SDN 040494, and households in the Valley of Sinabung Volcano, North Sumatera, Indonesia between June and October 2019. There were only two lowest categories of each WASH (Water, Sanitation and Hygiene) indicator. Multivariate analysis has also demonstrated a high likelihood of diarrhea among the population in limited settings for hygiene (p-value 0.012, AOR 7.892 95%CI 2.485, 25.064) and low daily income (p-value 0.015, AOR 3.079 95%CI 1.148, 8.260). Improvement of hygienic practices is mandatory as well as preventing volcanic eruption implications to the economy of the local community.

Low Osmolarity Oral Rehydration Salt Solution (LORS) in Management of Dehydration in Children

Justification

The IAP last published the guidelines “Comprehensive Management of Diarrhea” in 2006 and a review in 2016. The WHO in 2002 and the Government of India in 2004 recommended low osmolarity rehydration solution (LORS) as the universal rehydration solution for all ages and all forms of dehydration. However, the use of LORS in India continues to be unacceptably low at 51%, although awareness about ORS has increased from a mere 14% in 2005 to 69% in 2015. Availability of different compositions of ORS and brands in market added to the confusion.

Process

The Indian Academy of Pediatrics constituted a panel of experts from the fields of pediatrics, pediatric gastroenterology and nutrition to update on management of dehydration in children with particular reference to LORS and issue a current practice guideline. The committee met twice at CIAP HQ to review all published literature on the aspect. Brief presentations were made, followed by discussions. The draft paper was circulated by email. All relevant inputs and suggestions were incorporated to arrive at a consensus on this practice guideline.

Objectives

To summarize latest literature on ORT and empower pediatricians, particularly those practicing in rural areas, on management of dehydration by augmenting LORS use.

Recommendations

It was stressed that advantages of LORS far out-weigh its limitations. Increased use of LORS can only be achieved by promoting better awareness among public and health-care providers across all systems of medicine. LORS can also be useful in managing dehydration in non-diarrheal illness. More research is required to modify ORS further to make it safe and effective in neonates, severe acute malnutrition, renal failure, cardiac and other co-morbidities. There is an urgent need to discourage production and marketing all forms of ORS not in conformity with WHO approved LORS, under a slogan “One India, one ORS”.

Low Osmolarity Oral Rehydration Salt Solution (LORS) in Management of Dehydration in Children

JUSTIFICATION

The IAP last published the guidelines "Comprehensive Management of Diarrhea" in 2006 and a review in 2016. The WHO in 2002 and the Government of India in 2004 recommended low osmolarity rehydration solution (LORS) as the universal rehydration solution for all ages and all forms of dehydration. However, the use of LORS in India continues to be unacceptably low at 51%, although awareness about ORS has increased from a mere 14% in 2005 to 69% in 2015. Availability of different compositions of ORS and brands in market added to the confusion.

PROCESS

The Indian Academy of Pediatrics constituted a panel of experts from the fields of pediatrics, pediatric gastroenterology and nutrition to update on management of dehydration in children with particular reference to LORS and issue a current practice guideline. The committee met twice at CIAP HQ to review all published literature on the aspect. Brief presentations were made, followed by discussions. The draft paper was circulated by email. All relevant inputs and suggestions were incorporated to arrive at a consensus on this practice guideline.

OBJECTIVES

To summarize latest literature on ORT and empower pediatricians, particularly those practicing in rural areas, on management of dehydration by augmenting LORS use.

RECOMMENDATIONS

It was stressed that advantages of LORS far out-weigh its limitations. Increased use of LORS can only be achieved by promoting better awareness among public and health-care providers across all systems of medicine. LORS can also be useful in managing dehydration in non-diarrheal illness. More research is required to modify ORS further to make it safe and effective in neonates, severe acute malnutrition, renal failure, cardiac and other co-morbidities. There is an urgent need to discourage production and marketing all forms of ORS not in conformity with WHO approved LORS, under a slogan "One India, one ORS".

Description of Enteropathic Escherichia coli Species in Pediatric Patients at a Quaternary Children's Hospital

BACKGROUND

The epidemiology, demographics, clinical presentations, and outcomes associated with enteroaggregative Escherichia coli (EAEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC) pathotypes in US children are not well understood.

METHODS

This study was a retrospective chart review of all pediatric patients with a stool sample submitted to the Children's Hospital Colorado clinical microbiology laboratory for testing with the BioFire FilmArray Gastrointestinal Pathogen Panel from October 2015 through October 2017.

RESULTS

During the study period, 5692 patient stool samples were submitted; 679 (13%) were positive for EAEC, EPEC, or ETEC. Of note, 163/232 (70%) patients with EAEC, 282/493 (57%) with EPEC, and 49/58 (85%) with ETEC had detection of at least 1 other pathogen. Of all E. coli-positive stool samples, only 158/679 (23%) were from low-risk patients who were singly infected with EAEC, EPEC, or ETEC. In this cohort, most cases were associated with acute diarrhea (50%), abdominal pain (61%), and/or cramping (49%) and presented without fever (14%), emesis (28%), or lethargy (7%). Thirteen (8%) of these 158 patients received antibiotics at the time of their initial presentation to care. Of the 145 patients who did not receive antibiotics at their initial visit, 23 (16%) returned to care due to persistence of symptoms.

CONCLUSIONS

Our results suggest that the majority of patients singly infected with EAEC, EPEC, or ETEC present with mild, self-limited, gastrointestinal (GI) complaints. Further research is needed to determine what role these pathogens might play in children who present with chronic or inflammatory GI symptoms.

Etiologic features of diarrheagenic microbes in stool specimens from patients with acute diarrhea in Thailand

Many microbial species have been recognized as enteropathogens for humans. Here, we predicted the causative agents of acute diarrhea using data from multiplex quantitative PCR (qPCR) assays targeting 19 enteropathogens. For this, a case-control study was conducted at eight hospitals in Thailand. Stool samples and clinical data were collected from 370 hospitalized patients with acute diarrhea and 370 non-diarrheal controls. Multiple enteropathogens were detected in 75.7% and 13.0% of diarrheal stool samples using multiplex qPCR and bacterial culture methods, respectively. Asymptomatic carriers of enteropathogens were found among 87.8% and 45.7% of individuals by qPCR and culture methods, respectively. These results suggested the complexity of identifying causative agents of diarrhea. An analysis using the quantification cut-off values for clinical relevance drastically reduced pathogen-positive stool samples in control subjects from 87.8% to 0.5%, whereas 48.9% of the diarrheal stool samples were positive for any of the 11 pathogens. Among others, rotavirus, norovirus GII, Shigella/EIEC, and Campylobacter were strongly associated with acute diarrhea (P-value < 0.001). Characteristic clinical symptoms, epidemic periods, and age-related susceptibility to infection were observed for some enteropathogens. Investigations based on qPCR approaches covering a broad array of enteropathogens might thus improve our understanding of diarrheal disease etiology and epidemiological trends.

2017 Infectious Diseases Society of America Clinical Practice Guidelines for the Diagnosis and Management of Infectious Diarrhea

These guidelines are intended for use by healthcare professionals who care for children and adults with suspected or confirmed infectious diarrhea. They are not intended to replace physician judgement regarding specific patients or clinical or public health situations. This document does not provide detailed recommendations on infection prevention and control aspects related to infectious diarrhea.

FilmArray™ GI panel performance for the diagnosis of acute gastroenteritis or hemorragic diarrhea

Background

Acute gastroenteritis is a common cause of morbidity and mortality in humans worldwide. The rapid and specific identification of infectious agents is crucial for correct patient management. However, diagnosis of acute gastroenteritis is usually performed with diagnostic panels that include only a few pathogens. In the present bicentric study, the diagnostic value of FilmArray™ GI panels was assessed in unformed stool samples of patients with acute gastroenteritis and in a series of samples collected from pediatric patients with heamorragic diarrhea. The clinical performance of the FilmArray™ gastrointestinal (GI) panel was assessed in 168 stool samples collected from patients with either acute gastroenteritis or hemorragic diarrhea. Samples showing discordant results between FilmArray and routine methods were further analyzed with an additional assay.

Results

Overall, the FilmArray™ GI panel detected at least one potential pathogen in 92/168 (54.8%) specimens. In 66/92 (71.8%) samples, only one pathogen was detected, while in 26/92 (28.2%) multiple pathogens were detected.

The most frequent pathogens were rotavirus 13.9% (22/168), Campylobacter 10.7% (18/168), Clostridium difficile 9.5% (16/168), and norovirus 8.9% (15/168). Clostridium difficile was identified only in patients with acute gastroenteritis (p < 0.01), while STEC was detected exclusively in patients with hemorragic diarrhea (p < 0.01). In addition, Campylobacter spp., Salmonella spp., EPEC and E. coli producing Shiga-like toxin were more frequently detected in patients with hemorragic diarrhea (p < 0.05). The overall percent agreement calculated in samples was 73.8% and 65.5%, while 34.5% were discordant. After additional confirmatory analyses, the proportion of discordant samples decreased to 7.7%. Rotavirus and astrovirus were the most frequently unconfirmed pathogens.

Conclusion

In conclusion, the FilmArray™ GI panel has proved to be a valuable new diagnostic tool for improving the diagnostic efficiency of GI pathogens.

Variation in the limit-of-detection of the ProSpecT Campylobacter microplate enzyme immunoassay in stools spiked with emerging Campylobacter species

Campylobacter enteritis in humans is primarily associated with C. jejuni/coli infection. The impact of other Campylobacter spp. is likely to be underestimated due to the bias of culture methods towards Campylobacter jejuni/coli diagnosis. Stool antigen tests are becoming increasingly popular and appear generally less species-specific. A review of independent studies of the ProSpecT® Campylobacter Microplate enzyme immunoassay (EIA) developed for C. jejuni/coli showed comparable diagnostic results to culture methods but the examination of non-jejuni/coli Campylobacter spp. was limited and the limit-of-detection (LOD), where reported, varied between studies. This study investigated LOD of EIA for Campylobacter upsaliensis, Campylobacter hyointestinalis and Campylobacter helveticus spiked in human stools. Multiple stools and Campylobacter isolates were used in three different concentrations (10(4)-10(9)CFU/ml) to reflect sample heterogeneity. All Campylobacter species evaluated were detectable by EIA. Multivariate analysis showed LOD varied between Campylobacter spp. and faecal consistency as fixed effects and individual faecal samples as random effects. EIA showed excellent performance in replicate testing for both within and between batches of reagents, in agreement between visual and spectrophotometric reading of results, and returned no discordance between the bacterial concentrations within independent dilution test runs (positive results with lower but not higher concentrations). This study shows how limitations in experimental procedures lead to an overestimation of consistency and uniformity of LOD for EIA that may not hold under routine use in diagnostic laboratories. Benefits and limitations for clinical practice and the influence on estimates of performance characteristics from detection of multiple Campylobacter spp. by EIA are discussed.

ACG Clinical Guideline: Diagnosis, Treatment, and Prevention of Acute Diarrheal Infections in Adults

Acute diarrheal infections are a common health problem globally and among both individuals in the United States and traveling to developing world countries. Multiple modalities including antibiotic and non-antibiotic therapies have been used to address these common infections. Information on treatment, prevention, diagnostics, and the consequences of acute diarrhea infection has emerged and helps to inform clinical management. In this ACG Clinical Guideline, the authors present an evidence-based approach to diagnosis, prevention, and treatment of acute diarrhea infection in both US-based and travel settings.

Evaluation of PCR Based Assays for the Improvement of Proportion Estimation of Bacterial and Viral Pathogens in Diarrheal Surveillance

Diarrhea can be caused by a variety of bacterial, viral and parasitic organisms. Laboratory diagnosis is essential in the pathogen-specific burden assessment. In the pathogen spectrum monitoring in the diarrheal surveillance, culture methods are commonly used for the bacterial pathogens' detection whereas nucleic acid based amplification, the non-cultural methods are used for the viral pathogens. Different methodology may cause the inaccurate pathogen spectrum for the bacterial pathogens because of their different culture abilities with the different media, and for the comparison of bacterial vs. viral pathogens. The application of nucleic acid-based methods in the detection of viral and bacterial pathogens will likely increase the number of confirmed positive diagnoses, and will be comparable since all pathogens will be detected based on the same nucleic acid extracts from the same sample. In this study, bacterial pathogens, including diarrheagenic Escherichia coli (DEC), Salmonella spp., Shigella spp., Vibrio parahaemolyticus and V. cholerae, were detected in 334 diarrheal samples by PCR-based methods using nucleic acid extracted from stool samples and associated enrichment cultures. A protocol was established to facilitate the consistent identification of bacterial pathogens in diarrheal patients. Five common enteric viruses were also detected by RT-PCR, including rotavirus, sapovirus, norovirus (I and II), human astrovirus, and enteric adenovirus. Higher positive rates were found for the bacterial pathogens, showing the lower proportion estimation if only using culture methods. This application will improve the quality of bacterial diarrheagenic pathogen survey, providing more accurate information pertaining to the pathogen spectrum associated with finding of food safety problems and disease burden evaluation.

Comparative evaluation of the new xTAG GPP multiplex assay in the laboratory diagnosis of acute gastroenteritis. Clinical assessment and potential application from a multicentre Italian study

OBJECTIVE

Gastroenteritis caused by a single pathogen or multiple pathogens remains a major diagnostic challenge for the laboratory. The treatment of diarrhoea is based on microbiological results. Diagnosis is achieved using different laboratory techniques that have variable sensitivity and specificity. xTAG GPP is a new multiplex PCR assay that simultaneously detects 15 different pathogens responsible for diarrhoea. The results of the first multicentre study in Italy to evaluate the potential clinical application of the GPP assay in the laboratory diagnosis of diarrhoea are reported here.

METHODS

Faeces specimens (N=664) from hospitalized patients were tested with the GPP assay using a Luminex 200 instrument. All specimens were run using comparator methods following a routine algorithm: culture for bacteria, enzyme immunoassay and PCR for viruses, and microscopy for parasites.

RESULTS

Of the samples tested with the GPP, 53.61% (356/664) gave positive results, as compared to 45.33% by routine testing. Of the positive specimens, 34.55% showed the presence of genomic DNA from multiple pathogens. The Luminex method showed an increase in the percentage of positivity of 8.28%.

CONCLUSIONS

The GPP assay can be considered a helpful tool for the detection of gastrointestinal pathogens, with a hands-on time of 5h; it provides accurate data for the clinical management of hospitalized patients and for epidemiological surveillance.

Multicenter evaluation of the BioFire FilmArray gastrointestinal panel for etiologic diagnosis of infectious gastroenteritis

The appropriate treatment and control of infectious gastroenteritis depend on the ability to rapidly detect the wide range of etiologic agents associated with the disease. Clinical laboratories currently utilize an array of different methodologies to test for bacterial, parasitic, and viral causes of gastroenteritis, a strategy that suffers from poor sensitivity, potentially long turnaround times, and complicated ordering practices and workflows. Additionally, there are limited or no testing methods routinely available for most diarrheagenic Escherichia coli strains, astroviruses, and sapoviruses. This study assessed the performance of the FilmArray Gastrointestinal (GI) Panel for the simultaneous detection of 22 different enteric pathogens directly from stool specimens: Campylobacter spp., Clostridium difficile (toxin A/B), Plesiomonas shigelloides, Salmonella spp., Vibrio spp., Vibrio cholerae, Yersinia enterocolitica, enteroaggregative E. coli, enteropathogenic E. coli, enterotoxigenic E. coli, Shiga-like toxin-producing E. coli (stx1 and stx2) (including specific detection of E. coli O157), Shigella spp./enteroinvasive E. coli, Cryptosporidium spp., Cyclospora cayetanensis, Entamoeba histolytica, Giardia lamblia, adenovirus F 40/41, astrovirus, norovirus GI/GII, rotavirus A, and sapovirus. Prospectively collected stool specimens (n = 1,556) were evaluated using the BioFire FilmArray GI Panel and tested with conventional stool culture and molecular methods for comparison. The FilmArray GI Panel sensitivity was 100% for 12/22 targets and ≥94.5% for an additional 7/22 targets. For the remaining three targets, sensitivity could not be calculated due to the low prevalences in this study. The FilmArray GI Panel specificity was ≥97.1% for all panel targets. The FilmArray GI Panel provides a comprehensive, rapid, and streamlined alternative to conventional methods for the etiologic diagnosis of infectious gastroenteritis in the laboratory setting. The potential advantages include improved performance parameters, a more extensive menu of pathogens, and a turnaround time of as short as 1 h.

Multiple-aetiology enteric infections involving non-O157 Shiga toxin-producing Escherichia coli--FoodNet, 2001-2010

We describe multiple-aetiology infections involving non-O157 Shiga toxin-producing Escherichia coli (STEC) identified through laboratory-based surveillance in nine FoodNet sites from 2001 to 2010. A multiple-aetiology infection (MEI) was defined as isolation of non-O157 STEC and laboratory evidence of any of the other nine pathogens under surveillance or isolation of >1 non-O157 STEC serogroup from the same person within a 7-day period. We compared exposures of patients with MEI during 2001-2010 with those of patients with single-aetiology non-O157 STEC infections (SEI) during 2008-2009 and with those of the FoodNet population from a survey conducted during 2006-2007. In total, 1870 non-O157 STEC infections were reported; 68 (3.6%) were MEI; 60 included pathogens other than non-O157 STEC; and eight involved >1 serogroup of non-O157 STEC. Of the 68 MEI, 21 (31%) were part of six outbreaks. STEC O111 was isolated in 44% of all MEI. Of patients with MEI, 50% had contact with farm animals compared with 29% (P < 0.01) of persons with SEI; this difference was driven by infections involving STEC O111. More patients with non-outbreak-associated MEI reported drinking well water (62%) than respondents in a population survey (19%) (P < 0.01). Drinking well water and having contact with animals may be important exposures for MEI, especially those involving STEC O111.

Comparison of the BD MAX enteric bacterial panel to routine culture methods for detection of Campylobacter, enterohemorrhagic Escherichia coli (O157), Salmonella, and Shigella isolates in preserved stool specimens

We compared the BD MAX enteric bacterial panel (EBP) to culture for the detection of Salmonella, Shigella, Campylobacter, and Shiga toxin-producing enterohemorrhagic Escherichia coli (EHEC) O157 in seeded stool samples. The EBP panel demonstrated superior sensitivity and reliably detected Salmonella, EHEC O157, Shigella, and Campylobacter at concentrations 1- to 2-log10 lower than those needed for culture detection.

A quantitative polymerase chain reaction assay for rapid detection of 9 pathogens directly from stools of travelers with diarrhea

BACKGROUND & AIMS

Every year, 80 million tourists traveling to tropical and subtropical areas contract traveler's diarrhea (TD). Forty percent to 80% of cases are caused by bacteria, yet clinical diagnostic tests are available to identify only a few of the strains that cause TD. We aimed to develop a quantitative polymerase chain reaction (qPCR) assay to identify all major pathogens in stool samples.

METHODS

We developed a low-cost, high-throughput, multiplex qPCR assay for simultaneous detection of 9 bacterial pathogens in stool samples: Salmonella, Yersinia, Campylobacter, and Vibrio cholerae, as well as Shigella or enteroinvasive Escherichia coli, enterohemorrhagic E coli, enterotoxigenic E coli (ETEC), enteroaggregative E coli (EAEC), and enteropathogenic E coli (EPEC). The assay was validated using positive (n = 245) and negative (n = 243) control strains, as well as preselected positive and negative stool samples. In addition, stool samples were collected from 96 returning travelers with TD. The findings were compared with those from routine diagnostic tests.

RESULTS

The assay detected the bacterial strains with 100% sensitivity and specificity, compared with results from the reference tests. Of all stool samples collected from travelers with TD, EPEC was found in 47%, EAEC in 46%, ETEC in 22%, enterohemorrhagic E coli in 7%, Campylobacter in 6%, Shigella or enteroinvasive E coli in 2%, and Salmonella in 2%. Multiple pathogens were found in 37% of all samples.

CONCLUSIONS

We developed a low-cost, high-throughput qPCR assay for use in routine diagnostic analysis and research. It detects the pathogenic bacteria most commonly associated with TD in stool samples with 100% sensitivity and specificity, compared with reference methods. The assay requires 4 hours, whereas current detection methods require 1 to 7 days. At least 1 TD pathogen was identified in stool samples from 76% of returning travelers, whereas conventional methods found a pathogen in only 17%. The most commonly detected bacteria were EPEC, EAEC, and ETEC.

Survey of culture, goldengate assay, universal biosensor assay, and 16S rRNA Gene sequencing as alternative methods of bacterial pathogen detection

Cultivation-based assays combined with PCR or enzyme-linked immunosorbent assay (ELISA)-based methods for finding virulence factors are standard methods for detecting bacterial pathogens in stools; however, with emerging molecular technologies, new methods have become available. The aim of this study was to compare four distinct detection technologies for the identification of pathogens in stools from children under 5 years of age in The Gambia, Mali, Kenya, and Bangladesh. The children were identified, using currently accepted clinical protocols, as either controls or cases with moderate to severe diarrhea. A total of 3,610 stool samples were tested by established clinical culture techniques: 3,179 DNA samples by the Universal Biosensor assay (Ibis Biosciences, Inc.), 1,466 DNA samples by the GoldenGate assay (Illumina), and 1,006 DNA samples by sequencing of 16S rRNA genes. Each method detected different proportions of samples testing positive for each of seven enteric pathogens, enteroaggregative Escherichia coli (EAEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), Shigella spp., Campylobacter jejuni, Salmonella enterica, and Aeromonas spp. The comparisons among detection methods included the frequency of positive stool samples and kappa values for making pairwise comparisons. Overall, the standard culture methods detected Shigella spp., EPEC, ETEC, and EAEC in smaller proportions of the samples than either of the methods based on detection of the virulence genes from DNA in whole stools. The GoldenGate method revealed the greatest agreement with the other methods. The agreement among methods was higher in cases than in controls. The new molecular technologies have a high potential for highly sensitive identification of bacterial diarrheal pathogens.

Nonculture diagnostic tests for enteric diseases

The diagnosis of acute gastroenteritis (AGE) has traditionally been based on culture results of feces from patients with diarrhea. Virtually everything we know about disease and the epidemiology of enteric pathogens, such as Salmonella spp., Shiga toxin-producing Escherichia coli (STEC), e.g., O157, and Campylobacter spp., has been generated from the study of patients with culture-confirmed infections. However, this pattern may be changing because AGE diagnostics are moving away from culture toward rapid nonculture methods. These infections are mainly foodborne and therefore preventable, and it is of paramount importance that public health surveillance for these infections is consistent and reliable.

Simultaneous detection of six diarrhea-causing bacterial pathogens with an in-house PCR-luminex assay

Diarrhea can be caused by a range of pathogens, including several bacteria. Conventional diagnostic methods, such as culture, biochemical tests, and enzyme-linked immunosorbent assay (ELISA), are laborious. We developed a 7-plex PCR-Luminex assay to simultaneously screen for several of the major diarrhea-causing bacteria directly in fecal specimens, including pathogenic Aeromonas, Campylobacter jejuni, Campylobacter coli, Salmonella, Shigella, enteroinvasive Escherichia coli (EIEC), Vibrio, and Yersinia. We included an extrinsic control to verify extraction and amplification. The assay was first validated with reference strains or isolates and exhibited a limit of detection of 10(3) to 10(5) CFU/g of stool for each pathogen as well as quantitative detection up to 10(9) CFU/g. A total of 205 clinical fecal specimens from individuals with diarrhea, previously cultured for enteric pathogens and tested for Campylobacter by ELISA, were evaluated. Using these predicate methods as standards, sensitivities and specificities of the PCR-Luminex assay were 89% and 94% for Aeromonas, 89% and 93% for Campylobacter, 96% and 95% for Salmonella, 94% and 94% for Shigella, 92% and 97% for Vibrio, and 100% and 100% for Yersinia, respectively. All discrepant results were further examined by singleplex real-time PCR assays targeting different gene regions, which revealed 89% (55/62 results) concordance with the PCR-Luminex assay. The fluorescent signals obtained with this approach exhibited a statistically significant correlation with the cycle threshold (C(T)) values from the cognate real-time PCR assays (P < 0.05). This multiplex PCR-Luminex assay enables sensitive, specific, and quantitative detection of the major bacterial causes of gastroenteritis.