Fecal screening tests in the approach to acute infectious diarrhea: a scientific overview

Gut microbiota composition in travellers is associated with faecal lipocalin-2, a mediator of gut inflammation

Introduction

We examined the gut microbiota of travellers returning from tropical areas with and without traveller's diarrhoea (TD) and its association with faecal lipocalin-2 (LCN2) levels.

Methods

Participants were recruited at the Hospital Clinic of Barcelona, Spain, and a single stool sample was collected from each individual to perform the diagnostic of the etiological agent causing gastrointestinal symptoms as well as to measure levels of faecal LCN2 as a biomarker of gut inflammation. We also characterised the composition of the gut microbiota by sequencing the region V3-V4 from the 16S rRNA gene, and assessed its relation with the clinical presentation of TD and LCN2 levels using a combination of conventional statistical tests and unsupervised machine learning approaches.

Results

Among 61 participants, 45 had TD, with 40% having identifiable etiological agents. Surprisingly, LCN2 levels were similar across groups, suggesting gut inflammation occurs without clinical TD symptoms. Differential abundance (DA) testing highlighted a microbial profile tied to high LCN2 levels, marked by increased Proteobacteria and Escherichia-Shigella, and decreased Firmicutes, notably Oscillospiraceae. UMAP analysis confirmed this profile's association, revealing distinct clusters based on LCN2 levels. The study underscores the discriminatory power of UMAP in capturing meaningful microbial patterns related to clinical variables. No relevant differences in the gut microbiota composition were found between travellers with or without TD.

Discussion

The findings suggest a correlation between gut microbiome and LCN2 levels during travel, emphasising the need for further research to discern the nature of this relationship.

Relationship of Salmonella isolation with different serum and inflammatory intestinal parameters in natural fowl typhoid outbreaks from laying hens

Our study was undertaken to determine the best samples and selective-differential plating media to be used for Salmonella spp. isolation. We also compared hematological and serum biochemical values, Salmonella biovar Gallinarum (SG) detection (isolation and serological test), and inflammatory intestinal response (fecal leukocyte) in laying hens with naturally occurring fowl typhoid outbreaks. Furthermore, we looked for a biomarker of SG infection. Spleen, liver, ovarian follicle content, and bone marrow were found to be the best samples for SG isolation and the agreement between MacConkey-Salmonella Shigella agar was slight to excellent. The laying hens with SG isolation and rapid serum plate agglutination positive results showed a higher percentage of heterophils, heterophil/lymphocyte ratio and total white blood cells, and a lower percentage of lymphocytes than those with negative results. Furthermore, the positive fecal leukocyte samples had a higher percentage of heterophils, gamma-glutamyl transferase, total protein and globulin values than negative samples. Five biomarkers' cut-offs are proposed to distinguish between laying hens positive and negative to SG isolation.

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.

Novel Biomarkers and the Future Potential of Biomarkers in Inflammatory Bowel Disease

There is increasing importance placed upon noninvasive assessment of gut inflammation. These tools are likely to be the key in differentiating intestinal inflammatory disease from functional disorders and in monitoring the response to intervention in individuals with known inflammatory conditions. Although various noninvasive markers are currently available, they have limitations and do not provide ideal utility. This review focuses on emerging markers of gut inflammation, highlighting the potential of specific markers.

Laboratory systems as an antibacterial resistance containment tool in Africa

INTRODUCTION

As crucial as clinical laboratories are to preventing, identifying and managing resistance problems, laboratory scientists are among the most overlooked stakeholders. This review outlines the contributions that diagnostic laboratory systems should make toward all five of the World Health Organization's 2015 strategic objectives for antimicrobial resistance containment.

LABORATORY SYSTEMS IN RESISTANCE CONTAINMENT

Antimicrobial susceptibility testing and surveillance are central to antibacterial resistance management and control and need to be implemented more commonly and closer to sick patients. However, the scope of tests that promote judicious antimicrobial use extend beyond susceptibility testing. Laboratory tests for pathogens or their associated biomarkers confirm or rule out specific causes of signs and symptoms associated with infection. Laboratory systems also provide critical support to infection control programmes. All of these functions promote rational antimicrobial use and contain the spread of resistance. Routine laboratory data supports the development of vaccines and other technologies that could ease the pressure placed by antimicrobials. Laboratories are also a rich source of information for health professionals, policymakers and the general public about the urgency of the resistance problem and progress in containing it.

CONCLUSION

Laboratory systems are integral to antimicrobial resistance containment and contributions from African laboratories to addressing resistance need to be enhanced.

Relationship of Salmonella infection and inflammatory intestinal response with hematological and serum biochemical values in laying hens

There are few studies about the blood serum of laying hens infected with Salmonella. The differential leukocyte count and blood chemistry values are an important aid in the diagnosis of human diseases, but blood parameters in the avian species are not well known. On the other hand, invasive forms of bacterial gastroenteritis, like Salmonella, often cause intestinal inflammation so this study was undertaken to find a biomarker of Salmonella infection and inflammatory intestinal response in the hematological or serum biochemical parameters in laying hens. Furthermore, we evaluated the association of some farm characteristics with Salmonella infection and fecal leukocytes (FL). A fecal sample with at least one fecal leukocyte per field was considered positive for inflammatory intestinal response. False positive serum reactions for Salmonella infection, by serum plate agglutination (SPA) test, were reduced by heating the sample to 56°C for 30 min and then diluting it 5-fold. The range of hematological and biochemical parameter values was very wide, in addition, there was a poor agreement between the SPA and FL results. Comparison of the positive and negative samples in SPA and FL showed that 1.3% and 79.8% of the laying hens were positive and negative in both tests, respectively. Hens with a positive SPA result showed a higher percentage of monocytes than those with a negative SPA result. Hens with a positive FL test had a higher percentage of heterophils, ratio of heterophils to lymphocytes and aspartate aminotransferase values, while the percentage of lymphocytes was significantly lower (P < 0.05) than those with a negative FL test. The risk of Salmonella infection increased when the age of laying hens and the number of hens per poultry house was greater than or equal to 18 months old and 10,000 laying hens, compared to less than 18 months old and 10,000 laying hens, respectively. On the other hand, the risk of inflammatory intestinal response was higher in laying hens ≥ 18 months old than in hens < 18 months old. Despite the fact that we did not find any specific biomarker of Salmonella infection, this is the first report about the change of Salmonella infection and inflammatory response in hematological/serum biochemical values for laying hens.

Enteric parasites and enteroaggregative Escherichia coli in children from Cañazas County, Veraguas Province, Panama

This study was designed to examine the height-for-age z-scores (HAZ), and the prevalence of intestinal inflammation, gastrointestinal infections with parasites, and enteroaggregative Escherichia coli (EAEC) in rural Panamanian children. Stool microscopy and polymerase chain reaction (PCR) testing for EAEC detected Giardia lamblia (32%, 32 of 100) and EAEC (13%, 11 of 87) in the study participants, respectively. Anthropometric analyses showed that those children who were > 12 months of age had lower HAZ scores (mean of -1.449) than the reference population. As a group, the children in the study 1 to 5 years of age did not show recovery from the previously mentioned decline in terms of their HAZ. The HAZ means of the children infected with G. lamblia, EAEC, and Ascaris lumbricoides were -1.49, -1.67, and -2.11, respectively. Furthermore, the study participants with A. lumbricoides and EAEC infections in the presence of lactoferrin showed another decrease of 0.19 and 0.13, respectively, in their HAZ means.

Shigella in Brazilian children with acute diarrhoea: prevalence, antimicrobial resistance and virulence genes

Diarrhoeal disease is still considered a major cause of morbidity and mortality among children. Among diarrhoeagenic agents, Shigella should be highlighted due to its prevalence and the severity of the associated disease. Here, we assessed Shigella prevalence, drug susceptibility and virulence factors. Faeces from 157 children with diarrhoea who sought treatment at the Children's Hospital João Paulo II, a reference children´s hospital in Belo Horizonte, state of Minas Gerais, Brazil, were cultured and drug susceptibility of the Shigella isolates was determined by the disk diffusion technique. Shigella virulence markers were identified by polymerase chain reaction. The bacterium was recovered from 10.8% of the children (88.2% Shigella sonnei). The ipaH, iuc, sen and ial genes were detected in strains isolated from all shigellosis patients; set1A was only detected in Shigella flexneri. Additionally, patients were infected by Shigella strains of different ial, sat, sen and set1A genotypes. Compared to previous studies, we observed a marked shift in the distribution of species from S. flexneri to S. sonnei and high rates of trimethoprim/sulfamethoxazole resistance.

Cost utility of inflammation-targeted therapy for patients with ulcerative colitis

BACKGROUND & AIMS

Oral mesalamine drugs are frequently used to treat patients with mild-to-moderate ulcerative colitis (UC). However, these drugs are costly, and long-term adherence is poor. We compared the cost utility of inflammation-targeted, intermittent therapy with that of universal, continuous maintenance therapy with mesalamine agents for patients with mild-to-moderate UC.

METHODS

We developed a Markov cohort model that simulated a population of adult patients with newly diagnosed, quiescent UC after induction of remission with mesalamine agents. We obtained model inputs from the literature. The perspective taken was that of a short-term payer (health insurance provider) during a 5-year time period. We modeled 3 treatment strategies: symptom-targeted treatment (treatment for symptomatic disease flares only, SYMPT), continuous mesalamine maintenance for all patients (CONT, the current standard of care), and inflammation-targeted treatment (mesalamine therapy for only patients with a stool sample positive for an inflammatory marker, INFLAM). We measured disease flares, quality-adjusted life years (QALYs), costs (2009 U.S. dollars), and incremental cost-effectiveness ratios.

RESULTS

INFLAM was the least costly strategy (cumulative per-patient cost of $22,798), compared with $24,378 for the SYMPT and $25,621 for the CONT strategies. Despite the lower cost, INFLAM was comparable to SYMPT and CONT in effectiveness (4.4986 vs 4.5014 QALYs, respectively), making INFLAM the optimal strategy. Several variables were found to be important in sensitivity analysis; the CONT strategy was optimal only if the cost of mesalamine drugs was markedly reduced.

CONCLUSIONS

Inflammation-targeted treatment of patients with UC is effective and costs less than continuous treatment of all patients with mesalamine, the current standard of care. Prospective trials of inflammation-targeted treatment are warranted.

Usefulness of fecal lactoferrin in predicting and monitoring the clinical severity of infectious diarrhea

AIM: To explore the value of fecal lactoferrin in predicting and monitoring the clinical severity of infectious diarrhea.

METHODS: Patients with acute infectious diarrhea ranging from 3 mo to 10 years in age were enrolled, and one to three stool samples from each subject were collected. Certain parameters, including white blood cells /differential count, C-reactive protein, fecal mucus, fecal pus cells, duration of fever, vomiting, diarrhea and severity (indicated by Clark and Vesikari scores), were recorded and analyzed. Fecal lactoferrin was determined by enzyme-linked immunosorbent assay and compared in different pathogen and disease activity. Generalized estimating equations (GEE) were also used for analysis.

RESULTS: Data included 226 evaluations for 117 individuals across three different time points. Fecal lactoferrin was higher in patients with Salmonella (11.17 μg/g ± 2.73 μg/g) or Campylobacter (10.32 μg/g ± 2.94 μg/g) infections and lower in patients with rotavirus (2.82 μg/g ± 1.27 μg/g) or norovirus (3.16 μg/g ± 1.18 μg/g) infections. Concentrations of fecal lactoferrin were significantly elevated in patients with severe (11.32 μg/g ± 3.29 μg/g) or moderate (3.77 μg/g ± 2.08 μg/g) disease activity compared with subjects with mild (1.51 μg/g ± 1.36 μg/g) disease activity (P < 0.05). GEE analysis suggests that this marker could be used to monitor the severity and course of gastrointestinal infections and may provide information for disease management.

CONCLUSION: Fecal lactoferrin increased during bacterial infection and with greater disease severity and may be a good marker for predicting and monitoring intestinal inflammation in children with infectious diarrhea.

Fecal leukocytes in children infected with diarrheagenic Escherichia coli

The purpose of this study was to determine the presence and quantity of fecal leukocytes in children infected with diarrheagenic Escherichia coli and to compare these levels between diarrhea and control cases. We analyzed 1,474 stool samples from 935 diarrhea episodes and 539 from healthy controls of a cohort study of children younger than 2 years of age in Lima, Peru. Stools were analyzed for common enteric pathogens, and diarrheagenic E. coli isolates were studied by a multiplex real-time PCR. Stool smears were stained with methylene blue and read by a blinded observer to determine the number of polymorphonuclear leukocytes per high-power field (L/hpf). Fecal leukocytes at >10 L/hpf were present in 11.8% (110/935) of all diarrheal episodes versus 1.1% (6/539) in controls (P < 0.001). Among stool samples with diarrheagenic E. coli as the only pathogen isolated (excluding coinfection), fecal leukocytes at >10 L/hpf were present in 8.5% (18/212) of diarrhea versus 1.3% (2/157) of control samples (P < 0.01). Ninety-five percent of 99 diarrheagenic E. coli diarrhea samples were positive for fecal lactoferrin. Adjusting for the presence of blood in stools, age, sex, undernutrition, and breastfeeding, enterotoxigenic E. coli (ETEC) isolation as a single pathogen, excluding coinfections, was highly associated with the presence of fecal leukocytes (>10 L/hpf) with an odds ratio (OR) of 4.1 (95% confidence interval [CI], 1.08 to 15.51; P < 0.05). Although diarrheagenic E. coli was isolated with similar frequencies in diarrhea and control samples, clearly it was associated with a more inflammatory response during symptomatic infection; however, in general, these pathogens elicited a mild inflammatory response.

An epidemiologic review of enteropathogens in Gaborone, Botswana: shifting patterns of resistance in an HIV endemic region

BACKGROUND

The epidemiology of diarrheal disease in Botswana, an HIV endemic region, is largely unknown. Our primary objective was to characterize the prevalent bacterial and parasitic enteropathogens in Gaborone, Botswana. Secondary objectives included determining corresponding antimicrobial resistance patterns and the value of stool white and red blood cells for predicting bacterial and parasitic enteropathogens.

METHODOLOGY/PRINCIPAL FINDINGS

A retrospective cross-sectional study examined laboratory records of stool specimens analyzed by the Botswana National Health Laboratory in Gaborone, Botswana from February 2003 through July 2008. In 4485 specimens the median subject age was 23 [interquartile range 1.6-34] years. Overall, 14.4% (644 of 4485) of samples yielded a pathogen. Bacteria alone were isolated in 8.2% (367 of 4485), parasites alone in 5.6% (253 of 4485) and both in 0.5% (24 of 4485) of samples. The most common bacterial pathogens were Shigella spp. and Salmonella spp., isolated from 4.0% (180 of 4485) and 3.9% (175 of 4485) of specimens, respectively. Escherichia coli (22 of 4485) and Campylobacter spp. (22 of 4485) each accounted for 0.5% of pathogens. Comparing antimicrobial resistance among Shigella spp. and Salmonella spp. between two periods, February 2003 to February 2004 and July 2006 to July 2008, revealed an increase in ampicillin resistance among Shigella spp. from 43% to 83% (p<0.001). Among Salmonella spp., resistance to chloramphenicol decreased from 56% to 6% (p<0.001). The absence of stool white and red blood cells correlated with a high specificity and negative predictive value.

CONCLUSIONS/SIGNIFICANCE

Most gastroenteritis stools were culture and microscopy negative suggesting that viral pathogens were the majority etiologic agents in this Botswana cohort. Shigella spp. and Salmonella spp. were the most common bacteria; Isospora spp. and Cryptosporidium spp. were the most common parasites. Resistance to commonly used antimicrobials is high and should be closely monitored.

Acute bloody diarrhea: a medical emergency for patients of all ages

Acute bloody diarrhea should be considered a medical emergency. Its causes are frequently serious or actionable or both and are usually identified. However, acute bloody diarrhea as a stand-alone clinical presentation has received little scholarly attention in the past several decades. Although the range of possible causes of acute bloody diarrhea is broad, infectious considerations are paramount and should always be prioritized in the evaluation of such patients. History, examination, and laboratory testing should be focused on minimizing time to diagnosis (and, by extension, to implementing appropriate therapy). Strategically chosen tests and imaging, avoidance of extraneous diagnostic pursuits, and provision of supportive care while awaiting diagnostic clarity are central to the adroit management of patients with acute bloody diarrhea. Diagnostic considerations differ somewhat between adults and children but have many elements in common, including the need for vigilance in detecting Escherichia coli O157:H7 infection. In this review, we discuss diagnostic approaches (emphasizing the importance of rapid, accurate, and thorough microbiologic investigation) and measures that can be taken to support patients while awaiting information that determines the cause of their disease. These topics are discussed in the context of the medical care that is available to children and adults with bloody diarrhea in most institutions in developed nations.

Enteric infections and diagnostic testing

PURPOSE OF REVIEW

Gastrointestinal pathogens profoundly affect human health and well being. The provider's ability to render optimal care often highly depends on diagnostic microbiologic support. We aim to provide a clinically pertinent assessment of the current state of our ability to diagnose human gastrointestinal pathogens and describe (and decry) the unsophistication of many current diagnostic methods and strategies.

RECENT FINDINGS

Recent advances involve improved stool polymerase chain reaction assays and application of this technology to a broader panel of pathogens, stool antigen assays, and improved culture techniques, but there is little penetration of such diagnostic advances into clinical practice. Many such techniques remain limited to research or epidemiologic use and are not typically available in the clinical laboratory.

SUMMARY

Multiple clinical and laboratory factors need to be considered when attempting to diagnose the wide variety of gastrointestinal pathogens afflicting humans. Careful interpretation of diagnostic tests with attention to the population studied and the characteristics of each test is necessary.

Diagnostic approach to acute diarrheal illness in a military population on training exercises in Thailand, a region of campylobacter hyperendemicity

High rates of Campylobacter fluoroquinolone resistance highlight the need to evaluate diagnostic strategies that can be used to assist with clinical management. Diagnostic tests were evaluated with U.S. soldiers presenting with acute diarrhea during deployment in Thailand. The results of bedside and field laboratory diagnostic tests were compared to stool microbiology findings for 182 enrolled patients. Campylobacter jejuni was isolated from 62% of the cases. Clinical and laboratory findings at the time of presentation were evaluated to determine their impact on the posttest probability, defined as the likelihood of a diagnosis of Campylobacter infection. Clinical findings, the results of tests for inflammation (stool occult blood testing [Hemoccult], fecal leukocytes, fecal lactoferrin, plasma C-reactive protein), and the numbers of Campylobacter-specific antibody-secreting cells in peripheral blood failed to increase the posttest probability above 90% in this setting of Campylobacter hyperendemicity when these findings were present. Positive results by a Campylobacter-specific commercial enzyme immunoassay (EIA) and, less so, a research PCR were strong positive predictors. The negative predictive value for ruling out Campylobacter infection, defined as a posttest probability of less than 10%, was similarly observed with these Campylobacter-specific stool-based tests as well the fecal leukocyte test. Compared to the other tests evaluated, the Campylobacter EIA is a sensitive and specific rapid diagnostic test that may assist with diagnostic evaluation, with consideration of the epidemiological setting, logistics, and cost.

Fecal lactoferrin is a sensitive and specific marker of disease activity in children and young adults with inflammatory bowel disease

BACKGROUND AND AIMS

Fecal lactoferrin (FLA) is a neutrophil-derived surrogate marker of intestinal inflammation that is elevated in patients with inflammatory bowel disease. However, the correlation between FLA levels and serological markers of disease activity has not been previously reported, to our knowledge. In the present study we evaluated the ability of FLA levels to reflect disease activity in pediatric patients with inflammatory bowel disease. We further assessed the relationship between FLA levels and customary laboratory and clinical measures of inflammation.

PATIENTS AND METHODS

Fecal specimens were collected from 148 consecutive pediatric patients (79 with Crohn disease, 62 with ulcerative colitis, and 7 with irritable bowel syndrome) and 22 healthy control individuals. Lactoferrin was measured by enzyme-linked immunosorbent assay (IBD-SCAN, TECHLAB, Inc). Disease activity was assessed at the time of sample provision by laboratory measures (including erythrocyte sedimentation rate [ESR] and albumin) and previously validated disease activity indices (Pediatric Crohn Disease Activity Index, Kozarek, Harvey Bradshaw Activity Index).

RESULTS

Lactoferrin levels were significantly higher in patients with ulcerative colitis (1880 +/- 565 microg/mL) (mean +/- SE) or Crohn disease (1701 +/- 382 microg/mL) than in healthy control individuals under 21 years of age (1.17 +/- 0.47 microg/mL, P < 0.001). Lactoferrin levels correlated significantly with ESR, hematocrit, albumin, and platelet count (P < 0.001). Receiver operating characteristic curve analysis revealed that FLA levels were comparable to ESR in detecting patients with clinically active disease (P < 0.001). Patients who experienced a clinical flare within 2 months of specimen collection displayed higher lactoferrin levels (845 +/- 452 microg/mL) than did those who remained in clinical remission (190 +/- 90 microg/mL, P = 0.003).

CONCLUSIONS

Data presented here demonstrate that FLA is a sensitive and specific biochemical marker of inflammation for use in the diagnosis and interval assessment of pediatric patients with IBD, and its level correlates well with both clinical disease activity indices and ESR. Elevated levels of FLA may also identify patients at greater risk for the development of subsequent clinical flares.

The diagnostic value of serum interleukins 6 and 8 in children with acute gastroenteritis

OBJECTIVES

Early identification of the pathogen causing acute gastroenteritis in children helps the physicians managing the disease and prevents unnecessary antibiotic treatment. C-reactive protein (CRP), interleukin (IL) 6 and IL-8 play a major role in immune responses and have been studied in a large number of infectious and noninfectious inflammatory diseases. The purpose of this study was to determine the serum IL-6 and IL-8 concentrations early in the course of acute gastroenteritis to see if these cytokines were useful diagnostic markers in differentiating viral from bacterial gastroenteritis.

METHODS

Interleukin 6, IL-8 and CRP were measured in 18 patients with bacterial gastroenteritis, 21 patients with viral gastroenteritis and 17 healthy children.

RESULTS

Interleukin 6 and CRP concentrations in patients with bacterial gastroenteritis were significantly higher than those in patients with viral gastroenteritis and healthy controls (P < 0.001). IL-8 concentrations in patients with viral and bacterial gastroenteritis were both increased and were not statistically different. IL-6 and IL-8 levels had diagnostic sensitivities of 79% and 50% and specificities of 86% and 67%, respectively. The combination of IL-6 and CRP had a sensitivity of 94%, specificity of 71%, a positive predictive value of 74% and a negative predictive value of 93.75%.

CONCLUSIONS

Serum IL-6 may be a useful marker for early differentiation of viral and bacterial gastroenteritis in children, especially in combination with CRP.

Is Fecal Leukocyte Test a good predictor of Clostridium difficile associated diarrhea?

Background

Fecal leukocyte test (FLT) is widely used to screen for invasive diarrheas including C. difficile associated diarrhea (CDAD), which account for more than 25 % of all antibiotic associated diarrhea.

Method

263 stool samples from patients with suspected CDAD were studied simultaneously for fecal leukocyte test (FLT) and Clostridium difficile toxin assay (CDTA). FLT was performed by the Giemsa technique and CDTA was performed by enzyme immuno assay (EIA).

Results

Sensitivity, specificity, positive predictive value and negative predictive value of FLT as compared to CDTA were 30%, 74.9%, 13.2% and 89.3% respectively.

Conclusion

Considering the poor sensitivity of FLT, and the comparable cost and time of obtaining a CDTA at our institution, we conclude that FLT is not a good screening test for CDAD. Possible reasons for FLT being a poor predictor of CDTA are discussed.

A systematic review finds that diagnostic reviews fail to incorporate quality despite available tools

BACKGROUND AND OBJECTIVE

To review existing quality assessment tools for diagnostic accuracy studies and to examine to what extent quality was assessed and incorporated in diagnostic systematic reviews.

METHODS

Electronic databases were searched for tools to assess the quality of studies of diagnostic accuracy or guides for conducting, reporting or interpreting such studies. The Database of Abstracts of Reviews of Effects (DARE; 1995-2001) was used to identify systematic reviews of diagnostic studies to examine the practice of quality assessment of primary studies.

RESULTS

Ninety-one quality assessment tools were identified. Only two provided details of tool development, and only a small proportion provided any indication of the aspects of quality they aimed to assess. None of the tools had been systematically evaluated. We identified 114 systematic reviews, of which 58 (51%) had performed an explicit quality assessment and were further examined. The majority of reviews used more than one method of incorporating quality.

CONCLUSION

Most tools to assess the quality of diagnostic accuracy studies do not start from a well-defined definition of quality. None has been systematically evaluated. The majority of existing systematic reviews fail to take differences in quality into account. Reviewers should consider quality as a possible source of heterogeneity.

Enteroaggregative Escherichia coli: An emerging pathogen in children

Enteroaggregative Escherichia coli (EAEC) is an emerging pathogen that causes enteric and food-borne infectious diseases. Children throughout the world appear to be susceptible to EAEC infection. EAEC pathogenesis involves the following three stages: 1) adherence to the intestinal mucosa; 2) increased production and deposition of a mucus biofilm; and 3) mucosal toxicity due to inflammation and cytokine release. The HEp-2 cell adherent assay allows identification of EAECs characteristic aggregative or "stacked brick" adherence pattern. Antimicrobial treatment of children who develop an EAEC infection should be individually based. All children with EAEC diarrhea should receive adequate oral fluid hydration. For children who have persistent diarrhea and severe dehydrating illness despite having received adequate oral rehydration, antimicrobials may be initiated. Azithromycin and rifaximin have been shown to shorten the course of EAEC diarrhea in adults and probably represent the recommended antimicrobials of choice for children with severe or persistent illness. The objective of this review is to increase awareness of this important emerging pathogen and to discuss the epidemiology, pathogenesis, and pathogen and host factors associated with EAEC infection in children.

Performance assessment of the fecal leukocyte test for inpatients

Traditionally, fecal leukocyte testing detects large bowel inflammation or disruption, conditions that allow leukocytes into the stool. However, test usefulness with inpatients is unclear. Two hundred five inpatients who had undergone one to three tests were identified, and their FLT results were compared to their gastrointestinal disease diagnoses at time of discharge. A specificity of 92% for detecting intact colonic mucosae in inpatients was found.

Enteroaggregative Escherichia coli: an emerging enteric pathogen

Enteroaggregative Escherichia coli (EAEC) represents an emerging pathogen that causes enteric and food-borne infectious diseases. Subgroups in many populations throughout the world are susceptible to EAEC infection. EAEC pathogenesis involves adherence to the intestinal mucosa; increased production and deposition of a mucus biofilm; and mucosal toxicity due to inflammation and cytokine release. Due to the heterogeneity of EAEC strains and differing host immune responses, not all EAEC infections are symptomatic. Recent data suggest that individuals with a homozygous genotype -251 AA single nucleotide polymorphism (SNP), in the IL-8 promoter region, are more susceptible to EAEC diarrhea. The HEp-2 cell adherent assay allows identification of EAEC's characteristic aggregative or "stacked brick" adherence pattern. Antimicrobial treatment of individuals who develop EAEC diarrhea should be individually based. Ciprofloxacin and rifaximin, compared to placebo, have been shown to significantly shorten the course of diarrhea in patients who developed EAEC infection. The objective of this review is to increase awareness of this important emerging pathogen and to discuss the epidemiology, pathogenesis, and host-pathogen factors associated with EAEC infection.

Diagnostic accuracy of stool assays for inflammatory bacterial gastroenteritis in developed and resource-poor countries

Because acute bacterial gastroenteritis is often inflammatory, rapid stool assays that detect intestinal inflammation might be used to distinguish between bacterial and nonbacterial gastroenteritis. We performed meta-analyses to determine the discriminatory power, in developed and in resource-poor countries, of rapid stool assays that test for lactoferrin, fecal leukocytes, fecal erythrocytes, and occult blood. In developed countries, the area under the summary receiver operating characteristic curve (AUC/SROC) was 0.89 for fecal leukocytes and 0.81 for occult blood. In resource-poor countries, the AUC/SROC was 0.79 for lactoferrin, 0.72 for fecal leukocytes, 0.63 for occult blood, and 0.61 for fecal erythrocytes. In developed countries, positive and negative likelihood ratios (LR+ and LR-, respectively) for fecal leukocytes were 4.56 and 0.32 when a threshold of >5 cells/high-power field was used, compared with 2.94 and 0.6 in resource-poor countries; for lactoferrin, LR+ was 1.34 and LR- was 0.17 in resource-poor countries when the threshold was an agglutination rating of "+" and a dilution of 1:50. In developing countries, rapid stool assays performed poorly, whereas in developed countries, tests for fecal leukocytes, lactoferrin, and occult blood were moderately useful and could identify patients who were more likely to benefit from empirical antibiotic therapy.

Faecal lactoferrin as a predictor of positive faecal culture in south Indian children with acute diarrhoea

Faecal lactoferrin, an iron-based glycoprotein found concentrated in secondary granules of neutrophils, may serve as a surrogate marker of inflammation in the intestine. We evaluated the usefulness of faecal lactoferrin as a predictor of infection with invasive enteropathogens in 262 children with diarrhoea. Lactoferrin at a dilution of 1:50 had the highest sensitivity for detection not only of conventionally cultured invasive enteropathogens but also of all other enteropathogens. Neither individual clinical symptoms nor the identification of faecal leucocytes by microscopy significantly predicted isolation of invasive enteropathogens from the faeces of children with diarrhoea. Faecal lactoferrin is a simple test which showed promise in predicting which children with diarrhoea are likely to be infected with invasive pathogens and can be incorporated as a screening test before faecal cultures are undertaken in this population.

Asymmetric funnel plots and publication bias in meta-analyses of diagnostic accuracy

BACKGROUND

Despite the great possibility of publication bias in studies of diagnostic test research, empirical studies about publication bias have mainly focused on studies of treatment effect.

METHODS

A sample of 28 meta-analyses of diagnostic accuracy was selected from the Database of Abstracts of Reviews of Effectiveness (DARE). Methods used to deal with publication and related biases in these meta-analyses were examined. Asymmetry of funnel plot of estimated test accuracy against corresponding precision for each meta-analysis was assessed by three statistical methods: rank correlation method, regression analysis, and Trim and Fill method.

RESULTS

In reviews of diagnostic accuracy, there was a general lack of consideration of appropriate literature searching to minimize publication bias, and the impact of possible publication bias has not been systematically assessed. The results of the three different statistical methods consistently showed that in a large proportion of the 28 meta-analyses evaluated, the smaller studies were associated with a greater diagnostic accuracy. Exploratory analyses found that the fewer the literature databases searched, the greater the funnel plot asymmetry in meta-analyses. Funnel plot asymmetry tended to be greater in meta-analyses that included smaller number of primary studies. Our data revealed no consistent relationship between funnel plot asymmetry and language restriction in reviews.

CONCLUSIONS

Further research is required to explain why smaller studies tended to report greater test accuracy in a large proportion of meta-analyses of diagnostic tests. In systematic reviews of diagnostic studies, literature search should be sufficiently comprehensive and possible impact of publication bias should be assessed.

Laboratory approaches to infectious diarrhea

Future applications of advanced molecular diagnostics in clinical laboratories will enhance significantly capabilities to diagnose bacterial, parasitic, and viral agents in the early course of disease through enhanced assay sensitivities and specificities and improved turnaround times, theoretically leading to more timely and directed therapeutic intervention. Until such time, clinicians must continue to rely on clinical judgment and the diverse battery of traditional culture techniques, direct examination (including light microscopy and electron microscopy), and immunoassays that are available. Cost considerations and the ever-increasing array of infectious agents responsible for infectious gastroenteritis will continue to drive the development of practice guidelines to assist practitioners with reasoned and reasonable approaches to management of diarrheal illnesses.

Diarrhea in the returned traveler

Diarrhea in the returned traveler is a common problem that can be caused by a number of different pathogens. A history of the patient's travel and exposures, the duration of illness, the response to prior treatment, and the clinical syndrome can help to establish a good etiologic differential diagnosis on which further therapy can be based. Many of these patients can be treated empirically with antibiotics, either a fluoroquinolone or azithromycin, without further microbiologic evaluation. Those patients with severe or persistent disease or comorbid illnesses, or those who have failed empiric therapy, should undergo further microbiologic evaluation with directed stool cultures and ova and parasite screening. For those patients with negative evaluations, further empiric therapy may be warranted if syndromes are suggestive of specific agents of infection, such as by Giardia or Cyclospora species. Other patients may require endoscopic evaluation to exclude diagnoses such as tropical sprue or inflammatory bowel disease.

Fecal leukocyte stain has diagnostic value for outpatients but not inpatients

The methylene blue stain for fecal leukocytes (FL) is widely used as an adjunct to slower but more accurate tests of diarrheal etiology, such as stool culture (SCx) or toxin assays for Clostridium difficile. Prior studies investigating the utility of FL for predicting SCx and C. difficile toxin assay (CDTA) results did not evaluate the importance of inpatient versus outpatient status. We conducted a study of patients who submitted a stool specimen to the Stanford Hospital Microbiology Laboratory between May 1998 and April 1999. The results for stool specimens that were tested by FL and by a confirmatory test (either SCx or CDTA) were used to determine whether the FL method helped to predict the results of these tests. Of 797 stools that were tested by FL method and at least one confirmatory test, 502 stools were tested by CDTA, and 473 stools were cultured. The FL test was 14% sensitive and 90% specific for C. difficile with a diagnostic threshold of one white blood cell/high-power field (WBC/HPF). The overall likelihood ratio (LR) for a positive CDTA was 1.4 with a 95% confidence interval (CI) of 0. 5 to 3.7 (P = 0.5) and was similar among inpatients and outpatients. In contrast, the presence of >/=1 WBC/HPF was 52% sensitive and 88% specific for the 27 positive SCx results and helped to predict a positive SCx result (LR, 4.2; 95% CI, 2.7 to 6.5; P < 0.001). The sensitivity of >/=1 WBC/HPF was 57%, and its predictive value for SCx was higher among outpatients (outpatient LR, 5.0; 95% CI, 2.9 to 8.6; P < 0.001; inpatient LR, 1.9; 95% CI, 0.3 to 10.8; P = 0.5). Among inpatients, only 4 (1.5%) of the 273 SCx results were positive, and the presence of >/=1 WBC/HPF was insensitive (25%) and did not predict a positive SCx (LR, 1.9; 95% CI, 0.3 to 10.8; P = 0.5). When the data were reanalyzed using a diagnostic threshold of five WBC/HPF for FL, the predictive power of the FL method was similar. Thus, FL was of no value in predicting CDTA positivity, nor was it helpful in predicting SCx results for inpatients. Neither SCx nor the FL method should routinely be performed on samples from inpatients. Among outpatients, presence of FLs should suggest a bacterial diarrhea in clinically compatible cases.

Impact of simple screening criteria on utilization of low-yield bacterial stool cultures in a Children's Hospital

OBJECTIVE

To determine diagnostic yield of stool cultures for Salmonella, Shigella, Campylobacter jejuni, Yersinia enterocolitica, and Escherichia coli O157:H7 (SSCYE) among hospitalized children and to develop guidelines for appropriate use of these tests. Setting. Tertiary care pediatric hospital.

DESIGN

Computerized records from the Microbiology Laboratory from January 1992 to December 1996 were reviewed retrospectively to collect data on the number of stool cultures performed in inpatients and outpatients, the length of hospital stay at the time cultures were sent, and diagnostic yield of cultures in hospitalized patients. A detailed review of medical records of all patients with a stool pathogen isolated after 3 days of hospitalization was also undertaken. The results from this retrospective analysis were used to develop guidelines to reduce unwarranted stool cultures and to educate medical care providers in the appropriate use of these tests. The impact of these guidelines on reduction in the volume of stool cultures performed on hospitalized patients was measured prospectively from January 1998 to June 1998.

RESULTS

A total of 27 110 stool cultures for SSCYE were performed in the 5-year study period. Of the 14 125 cultures from inpatients, 174 (1.2%) were positive. Among the cultures from inpatients, 9378 (66%) were from patients hospitalized for >3 days. Only 13 (.14%) were positive. Of these 13 cultures, 4 represented nosocomial infections, whereas the remaining 9 cultures either were sent to document clearance from a patient known previously to be infected with an enteric pathogen (7), or were attributed to delayed testing in individuals admitted with a diarrheal illness (2). Introduction of guidelines to reject all SSCYE cultures from patients hospitalized for >3 days who did not meet specified criteria was associated with an overall reduction of 689 (43%) in the volume of tests performed in the 6-month period evaluated. This included 497 fewer cultures ordered and 192 cultures that were ordered but rejected because screening criteria were not met. Only 11 (5.4%) of 203 cultures sent >3 days after admission were processed because they met clinical criteria for testing. None were positive. Estimated cost savings were $50 163/year.

CONCLUSIONS

Stool cultures for SSCYE among hospitalized patients have very low diagnostic yield and are extremely overutilized. Simple guidelines, such as rejecting (with few exceptions) cultures from patients hospitalized for >3 days, can reduce substantially such unnecessary testing.

Infectious Enteritis

Initial management of acute infectious enteritis should focus on fluid and electrolyte repletion and symptomatic care. A decision to prescribe empiric antibiotic therapy should rest on clinical or epidemiologic features of the illness that suggest a treatable bacterial origin or a high-risk host. This decision should be reinforced by the detection of leukocytes or blood in the stool. If empiric therapy is indicated, a quinolone is generally the best initial choice. A stool culture yielding an enteropathogen should generally be specifically treated. A possible exception is uncomplicated Salmonella gastroenteritis in an otherwise healthy host. Nosocomial diarrhea is caused by Clostridium difficile in a minority of cases. Because diagnostic studies for this pathogen are sufficiently sensitive and specific, empiric antibiotic treatment for C. difficile is seldom indicated. Diarrhea in AIDS patients is best worked up and managed in a stepwise fashion, beginning with simple measures. Endoscopy or surgery are seldom indicated in the evaluation and management of infectious enteritis.

Utility of a rapid fecal latex agglutination test detecting the neutrophil protein, lactoferrin, for diagnosing inflammatory causes of chronic diarrhea

OBJECTIVE

The utility of tests for fecal neutrophils in the setting of chronic diarrhea has not been established. The purpose of this study was to determine the causes of chronic diarrhea associated with fecal neutrophils.

METHODS

One fecal specimen from each of 10 normal subjects, 26 patients with known microscopic colitis, 13 with celiac sprue, eight with Crohn's disease, four with ulcerative colitis, and 103 with chronic diarrhea of unknown origin, as well as 10 fecal specimens from a patient with chronic nongranulomatous enterocolitis were analyzed blindly for the presence of a neutrophil granule protein called lactoferrin using a commercial latex agglutination kit. Diagnostic evaluation of the 103 patients with chronic diarrhea was carried out to determine the diagnostic accuracy of this test for chronic inflammatory bowel disease.

RESULTS

None of the normal control subjects, three of 39 patients with microscopic colitis or celiac sprue, all 10 specimens from the patient with enterocolitis, and all 12 control patients with ulcerative colitis or Crohn's disease had a positive fecal lactoferrin test. Eleven of 103 patients with chronic diarrhea presenting without a diagnosis had a positive test, and all were diagnosed with an inflammatory condition of the colon (five-, ulcerative colitis; four-, Crohn's disease; one-, ischemic colitis; and one-, microscopic colitis). Only one patient with inflammatory bowel disease had a negative lactoferrin test. The sensitivity, specificity, and positive and negative predictive values of the fecal lactoferrin test for ulcerative or Crohn's colitis were 90%, 98%, 82%, and 99%, respectively.

CONCLUSION

The major cause of fecal neutrophils in patients with chronic diarrhea is chronic inflammatory bowel disease of the colon. The latex agglutination test for fecal lactoferrin offers a highly sensitive, specific, and simple means for detection of fecal neutrophils in these patients.

Fecal lactoferrin, fecal leukocytes and occult blood in the diagnostic approach to childhood invasive diarrhea

OBJECTIVE

To compare fecal screening tests in the diagnostic approach to childhood invasive diarrhea.

SETTING AND PATIENTS

We assessed 125 consecutive children with acute diarrhea for fecal lactoferrin, fecal leukocytes and occult blood from November, 1995, to June, 1996.

RESULTS

Lactoferrin showed a greater overall sensitivity than fecal leukocytes or occult blood for detecting invasive pathogens. Combinations of lactoferrin or fecal leukocytes and of lactoferrin or occult blood or both yielded sensitivities and negative predictive values close to 100%, being superior to all other combinations. All patients with full breast-feeding and mixed feeding had a positive lactoferrin test with a 1:50 dilution used as the cutoff. In controls without diarrhea being exclusively bottle-fed, 3 of 15 (20%) still showed a positive lactoferrin result at the dilution of 1:50. This compared with 15 of 15 (100%) positive results among controls fully breast-fed, 14 of 15 (93%) among controls predominantly breast-fed and 11 of 15 (73%) among control children predominantly bottle-fed.

CONCLUSIONS

This study confirms the usefulness of lactoferrin testing as a negative predictor. Breast-feeding lowers the specificity of the test but does not alter the sensitivity. Fecal lactoferrin may be viewed as the screening test of choice to avoid expensive stool cultures in the diagnostic approach to invasive diarrhea.