Travelers' diarrhea and toxigenic Escherichia coli

Travellers' diarrhoea - prevention, trends and role of microbiome

OBJECTIVES

In this review, we present a contemporary look at the management of travellers' diarrhoea (TD), and we discuss the potential role of a microbiome as well as the administration of live microorganisms in order to prevent TD.

METHODS

We performed a comprehensive search using the PubMed and Web of Science databases for the period 2014-2021, looking for original and review articles on travellers' diarrhoea.

RESULTS

TD belongs among the most frequent illnesses experienced by travellers. For the most part, it is manifested as an acute yet self limiting condition, and only in a few cases proceeds to a prolonged form. Epidemiological analyses have shown that the majority of TD cases are caused by bacterial infections. In practice, pharmacological therapy is often used in the prevention and treatment of TD, since patients naturally seek preventive measures against the development of its severe course and its impact on planned activities. Bismuth salicylate is a strongly recommended TD prophylaxis but is not available on all European Union markets. Although the antibiotic prophylaxis is not generally recommended in guidelines, some antibiotic or chemotherapeutic agents are accessible over-the-counter in certain countries, and travellers are routinely encouraged to use them preventively. This routine can alter the microbiome of the traveller and promote the spread of drug resistant bacteria in their place of residence. Probiotic administration is considered safe, although the quality of evidence in favour of its prophylactic use in TD is currently low.

CONCLUSIONS

The challenge for public health authorities is to educate personnel that can directly influence the behaviour of travellers through safe and effective pharmacological alternatives to antibiotics. Manipulation of the gut microbiome using specific probiotic strains can represent a safe and promising intervention.

Evaluation and Management of Traveler's Diarrhea in Children

Traveler's diarrhea is the most common travel disease in both children and adults. Adult guidelines for traveler's diarrhea have been established, but significant gaps persist in guidance for the evaluation and management of pediatric traveler's diarrhea. Adult guidelines are not necessarily applicable in children, and it is essential for clinicians to account for the differences in pediatric pathophysiology, clinical presentations, and treatment recommendations when evaluating and managing pediatric traveler's diarrhea.

Visualization-assisted binning of metagenome assemblies reveals potential new pathogenic profiles in idiopathic travelers' diarrhea

BACKGROUND

Travelers' diarrhea (TD) is often caused by enterotoxigenic Escherichia coli, enteroaggregative E. coli, other bacterial pathogens, Norovirus, and occasionally parasites. Nevertheless, standard diagnostic methods fail to identify pathogens in more than 40% of TD patients. It is predicted that new pathogens may be causative agents of the disease.

RESULTS

We performed a comprehensive amplicon and whole genome shotgun (WGS) metagenomic study of the fecal microbiomes from 23 TD patients and seven healthy travelers, all of which were negative for the known etiologic agents of TD based on standard microbiological and immunological assays. Abnormal and diverse taxonomic profiles in TD samples were revealed. WGS reads were assembled and the resulting contigs were visualized using multiple query types. A semi-manual workflow was applied to isolate independent genomes from metagenomic pools. A total of 565 genome bins were extracted, 320 of which were complete enough to be characterized as cellular genomes; 160 were viral genomes. We made predictions of the etiology of disease for many of the individual subjects based on the properties and features of the recovered genomes. Multiple patients with low-diversity metagenomes were predominated by one to several E. coli strains. Functional annotation allowed prediction of pathogenic type in many cases. Five patients were co-infected with E. coli and other members of Enterobacteriaceae, including Enterobacter, Klebsiella, and Citrobacter; these may represent blooms of organisms that appear following secretory diarrhea. New "dark matter" microbes were observed in multiple samples. In one, we identified a novel TM7 genome that phylogenetically clustered with a sludge isolate; it carries genes encoding potential virulence factors. In multiple samples, we observed high proportions of putative novel viral genomes, some of which form clusters with the ubiquitous gut virus, crAssphage. The total relative abundance of viruses was significantly higher in healthy travelers versus TD patients.

CONCLUSION

Our study highlights the strength of assembly-based metagenomics, especially the manually curated, visualization-assisted binning of contigs, in resolving unusual and under-characterized pathogenic profiles of human-associated microbiomes. Results show that TD may be polymicrobial, with multiple novel cellular and viral strains as potential players in the diarrheal disease.

OU. Current approaches to prophylaxis and treatment of travelers’ diarrhea

Travelers’ diarrhea is the most common infectious disease in this subpopulation and usually develops within the first week of travel. This review presents summarized data on epidemiology and etiology of travelers’ diarrhea. Nonspecific precautions and medical treatments (antimicrobials, probiotics) to prevent this infection are described in detail. Current approaches to the treatment of travelers’ diarrhea (oral rehydration, probiotics, anti­diarrheals, antimicrobials) in adults and children depending on disease severity are also considered.

Assessing antigen specific HLA-DR+ antibody secreting cell (DR+ASC) responses in whole blood in enteric infections using an ELISPOT technique

Antibody secreting cells (ASCs) generate antibodies in an antigen-specific manner as part of the adaptive immune response to infections, and these cells increase their surface expression of HLA-DR. We have studied this parameter (HLA-DR+ ASC) in patients with recent diarrheal infection using immuno-magnetic cell sorting and an enzyme linked immunospot (ELISPOT) technique that requires only one milliliter of blood. We validated this approach in adult patients with cholera (n = 15) or ETEC diarrhea (n = 30) on days 2, 7 and 30 after showing clinical symptom at the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) hospital in Dhaka, and we compared responses to age-matched healthy controls (n = 7). We found that HLA-DR+ ASC (DR+ASC) responses specific both for T cell-dependent (cholera toxin B subunit), and T cell-independent (lipopolysaccharide) antigens were elevated at day 7 after showing clinical cholera symptom. Similarly, DR+ASCs were elevated against both heat-labile toxin and colonization factors following ETEC infection. We observed significant correlations between antigen-specific DR+ASC responses and antigen-specific, gut homing ASC and plasma antibody responses. This study demonstrates that a simple ELISPOT procedure allows determination of antigen-specific ASC responses using a small volume of whole blood following diarrhea. This technique may be particularly useful in studying DR+ASC responses in young children and infants, either following infection or vaccination.

Medications for the prevention and treatment of travellers' diarrhea

BACKGROUND

. Travellers' diarrhea (TD) remains one of the most common illnesses encountered by travellers to less developed areas of the world. Because bacterial pathogens such as enterotoxigenic Escherichia coli (ETEC), enteroaggregative E. coli , Campylobacter spp. and Shigella spp. are the most frequent causes, antibiotics have been useful in both prevention and treatment of TD.

METHODS.

Results of trials that assessed the use of medications for the prevention and treatment of TD were identified through PubMed and MEDLINE searches using search terms 'travellers' diarrhea', 'prevention' and 'treatment'. References of articles were also screened for additional relevant studies.

RESULTS.

Prevention of TD with antibiotics has been recommended only under special circumstances. Doxycycline, trimethoprim-sulfamethoxazole, fluoroquinolones and rifaximin have been used for prevention, but at present the first three antibiotics may have limited use secondary to increasing resistance, leaving rifaximin as the only current option. Bismuth subsalicylate (BSS) (Pepto-Bismol tablets) is also an option for prophylaxis. Treatment with antibiotics has been recommended for moderate to severe TD. Azithromycin is the drug of choice, especially in Asia where Campylobacter is common. Fluoroquinolone antibiotics continue to be effectively used in Latin America and Africa where ETEC is predominant. BSS and loperamide (LOP) also are effective as standalone treatments. LOP may be used alone for treatment of mild TD or in conjunction with antibiotics for treatment of TD.

CONCLUSIONS

. Historically, antibiotic prophylaxis has not been routinely recommended and has been reserved for special circumstances such as when a traveller with an underlying illness cannot tolerate TD. Antibiotics with or without LOP have been useful in shortening the duration and severity of TD. Emerging antibiotic resistance, limited new antibiotic alternatives and faecal carriage of antibiotic-resistant bacteria by travellers may prompt a re-evaluation of classic recommendations for treatment and prevention of TD with antibiotics.

International Travelers' Sociodemographic, Health, and Travel Characteristics: An Italian Study

BACKGROUND

Approximately the 8% of travelers requires medical care, with the diagnosis of a vaccine-preventable disease. The aim of our study was to analyze the socio-demographic, health and travel characteristics of the Italian international travelers.

METHODS

We conducted a cross sectional study from January 2015 to June 2016, at the Travel Medicine Clinic of Siena, asking the doctor to interview patients who attended the Clinic, recording socio-demographic and travel information, malaria prophylaxis, vaccinations. The data were organized in a database and processed by software Stata®.

RESULTS

We collected 419 questionnaires. Patients chose 71 countries for their travels; the favorite destinations were: India (6.31%), Thailand (6.31%), and Brazil (5.10%). The mean length of stay was 36.17 days. Italians, students, and freelancers tended to stay abroad for a longer time (mean: 36.4 days, 59.87 days and 64.16 days respectively). 33.17% of our sample used drugs for malaria chemoprophylaxis: 71.9% of them used Atovaquone/Proguanil (Malarone®), 26.6% used Mefloquine (Lariam®), 1.5% other drugs. The vaccinations that travelers mostly got in our study were to prevent hepatitis A (n = 264), the typhoid fever (n = 187), the Tetanus + Diphtheria + Pertussis (n = 165), the Yellow fever (n = 118) and the cholera (n = 78). Twenty-eight (6.68%) refused some recommended vaccinations. The vaccines mostly refused were for Typhoid fever (n = 20), hepatitis a (n = 9), and cholera (n = 9).

CONCLUSION

Our results demonstrated that Italian international travelers are at-risk because of their poor vaccinations adherence. This implies that pre-travel counseling is fundamental to increase the knowledge of the risks and the compliance of future travelers.

Real-Time TaqMan PCR Assay for the Detection of Heat-Labile and Heat-Stable Enterotoxin Genes in a Geographically Diverse Collection of Enterotoxigenic Escherichia coli Strains and Stool Specimens

Enterotoxigenic Escherichia coli (ETEC) are an important cause of diarrhea in children under the age of 5 years in developing countries and are the leading bacterial agent of traveler's diarrhea in persons traveling to these countries. ETEC strains secrete heat-labile (LT) and/or heat-stable (ST) enterotoxins that induce diarrhea by causing water and electrolyte imbalance. We describe the validation of a real-time TaqMan PCR (RT-PCR) assay to detect LT, ST1a, and ST1b enterotoxin genes in E. coli strains and in stool specimens. We validated LT/ST1b duplex and ST1a single-plex RT-PCR assay using a conventional PCR assay as a gold standard with 188 ETEC strains and 42 non-ETEC strains. We validated LT/ST1b duplex and ST1a single-plex RT-PCR assay in stool specimens (n = 106) using traditional culture as the gold standard. RT- PCR assay sensitivities for LT, ST1a, and ST1b detection in strains were 100%, 100%, and 98%; specificities were 95%, 98%, and 99%, and Pearson correlation coefficient r was 0.9954 between RT-PCR assay and the gold standard. In stool specimens, RT-PCR assay sensitivities for LT, ST1a, and ST1b detection were 97%, 100%, and 97%; and specificities were 99%, 94%, and 97%. Pearson correlation coefficient r was 0.9975 between RT-PCR results in stool specimens and the gold standard. Limits of detection of LT, ST1a, and ST1b by RT-PCR assay were 0.1 to1.0 pg/μL and by conventional PCR assay were 100 to1000 pg/μL. The accuracy, rapidity and sensitivity of this RT-PCR assay is promising for ETEC detection in public health/clinical laboratories and for laboratories in need of an independent method to confirm results of other culture independent diagnostic tests.

Diarrhoea in a large prospective cohort of European travellers to resource-limited destinations

BACKGROUND

Incidence rates of travellers' diarrhoea (TD) need to be updated and risk factors are insufficiently known.

METHODS

Between July 2006 and January 2008 adult customers of our Centre for Travel Health travelling to a resource-limited country for the duration of 1 to 8 weeks were invited to participate in a prospective cohort study. They received one questionnaire pre-travel and a second one immediately post-travel. First two-week incidence rates were calculated for TD episodes and a risk assessment was made including demographic and travel-related variables, medical history and behavioural factors.

RESULTS

Among the 3100 persons recruited, 2800 could be investigated, resulting in a participation rate of 89.2%. The first two-weeks incidence for classic TD was 26.2% (95%CI 24.5-27.8). The highest rates were found for Central Africa (29.6%, 95% CI 12.4-46.8), the Indian subcontinent (26.3%, 95%CI 2.3-30.2) and West Africa (21.5%, 95%CI 14.9-28.1). Median TD duration was 2 days (range 1-90). The majority treated TD with loperamide (57.6%), while a small proportion used probiotics (23.0%) and antibiotics (6.8%). Multiple logistic regression analysis on any TD to determine risk factors showed that a resolved diarrhoeal episode experienced in the 4 months pre-travel (OR 2.03, 95%CI 1.59-2.54), antidepressive comedication (OR 2.11, 95%CI 1.17-3.80), allergic asthma (OR 1.67, 95%CI 1.10-2.54), and reporting TD-independent fever (OR 6.56, 95%CI 3.06-14.04) were the most prominent risk factors of TD.

CONCLUSIONS

TD remains a frequent travel disease, but there is a decreasing trend in the incidence rate. Patients with a history of allergic asthma, pre-travel diarrhoea, or of TD-independent fever were more likely to develop TD while abroad.

Development of a DNA microarray for detection and serotyping of enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a common pathogen worldwide causing infectious diarrhea, especially traveler's diarrhea. Traditional physiological assays, immunoassays, and PCR-based methods for the detection of ETEC target the heat-labile enterotoxin and/or the heat-stable enterotoxin. Separate serotyping methods using antisera are required to determine the ETEC serogroup. In this study, we developed a DNA microarray that can simultaneously detect enterotoxin genes and the 19 most common O serogroup genes in ETEC strains. The specificity and reproducibility of this approach were verified by hybridization to 223 strains: 50 target reference or clinical strains and 173 other strains, including those belonging to other E. coli O serogroups and closely related species. The sensitivity of detection was determined to be 50 ng of genomic DNA or 10(8) CFU per ml of organisms in pure culture. The random PCR strategy used in this study with minimal bias provides an effective alternative to multiplex PCR for the detection of pathogens using DNA microarrays. The assay holds promise for applications in the clinical diagnosis and epidemiological surveillance of pathogenic microorganisms.

Expert review of the evidence base for prevention of travelers' diarrhea

The most frequent illness among persons traveling from developed to developing countries is travelers' diarrhea. Travelers to high-risk regions traditionally have been educated to exercise care in food and beverage selection. Innovative research is needed to identify ways to motivate people to exercise this care and to determine its value. Chemoprophylaxis can be recommended for certain groups while monitoring for safety, drug resistance, and efficacy against all forms of bacterial diarrhea. Research to evaluate the value of immunoprophylaxis is recommended. In the following document, the authors used an evidence base when available to determine strength and quality of evidence and when data were lacking, the panel experts provided consensus opinion.

Enterotoxigenic Escherichia coli and diffusely adherent E. coli as likely causes of a proportion of pathogen-negative travelers' diarrhea--a PCR-based study

BACKGROUND

Enteropathogens cannot be identified in 40% to 50% of subjects with travelers' diarrhea (TD).

METHODS

We used polymerase chain reaction (PCR) methods to look for the presence of two bacterial causes of diarrhea in a large group of international travelers after failing to detect a pathogen by conventional tests. DNA was isolated from the diarrheal stool and subjected to PCR from 162 subjects from whom we earlier failed to identify a pathogen in a previous study and included 54 from Antigua, Guatemala, 39 from Guadalajara, Mexico, 29 from Kolkata, India, and 40 from Goa, India. Gene products for enterotoxigenic Escherichia coli (ETEC)--LT (heat-labile enterotoxin) and ST (heat-stable enterotoxin)--and diffusely adherent E. coli (DAEC), afa/dr (Afa fimbrial and Dr nonfimbrial family of adhesins), were used.

RESULTS

At least one gene product was identified in diarrhea stool samples of 47 of 162 (29%) subjects. ETEC virulence genes (LT, ST) were found in 34 (21%) samples studied, with rates of occurrence ranging from 8% in Goa to 39% for the samples from Guatemala (p = 0.0006). A large number of ST-only strains explained the high ETEC rate in Guatemala. DAEC afa/dr family of adhesions was identified in between 8 and 14% of the samples.

CONCLUSIONS

ETEC and DAEC were implicated in nearly one-third of the subjects initially diagnosed as pathogen negative. Direct PCR results from stools are consistent with the previous assumption that most undiagnosed TD is bacterial in nature and also highlights the potential value that PCR can add to studies designed to evaluate treatment and preventive interventions for TD, including vaccines.

Regulation of active ion transport in the small intestine

The epithelium of the small intestine can both actively absorb and actively secrete electrolytes and water. Secretion can be elicited in vitro by adding cyclic AMP or a stimulator of intestinal mucosal adenylate cyclase (cholera and Escherichia coli enterotoxins, prostaglandins, vasoactive intestinal peptide) or an inhibitor of cyclic AMP phosphodiesterase (theophylline). Cyclic AMP appears to alter intestinal ion transport at two different loci: it inhibits a coupled influx process for Na+ and Cl- at the luminal border, thereby reducing active absorption of NaCl, and it also stimulates the active secretion of anion (or Na+ and anion). A variety of evidence suggests that these two effects of cyclic AMP reside in different types of cells, the former in villus cells and the latter in crypt cells. The latter process is Na+-dependent and is inhibited by low concentrations of ouabain and ethacrynic acid. Active ion absorption in vitro can be enhanced by (1) stimulating Na+-coupled organic solute absorption with glucose, amino acids and possibly also oligo peptides; (2) reducing the HCO3- concentration and/or pH of the serosal bathing solution; and (3) introducing an alpha-adrenergic agonist. Cholera toxin-induced fluid production in vivo can be diminished by the first of these manoeuvres. The in vivo efficacies of the other two have not been evaluated.

The problem of bacterial diarrhoea

The reported incidence of "pathogenic" bacteria, as judged by serotype, in the stools of children with acute diarrhoea has varied from 4 to 33% over the last twenty years. Techniques such as tissue culture provide a means for detecting enterotoxin-producing strains of bacteria, strains which often do not possess "pathogenic" serotypes. "Pathogenicity" requires redefinition, and the aetiological importance of bacteria in diarrhoea is probably considerably greater than previous reports have indicated. Colonization of the bowel by a pathogen will result in structural and/or mucosal abnormalities, and will depend on a series of complex interactions between the external environment, the pathogen, and the host and its resident bacterial flora. Enteropathogenic bacteria may be broadly classified as (i) invasive (e.g. Shigella, Salmonella and some Escherichia coli) which predominantly affect the distal bowel, or (ii) non-invasive (e.g. Vibrio cholerae and E. coli) which affect the proximal bowel. V. cholerae and E. coli elaborate heat-labile enterotoxins which activate adenylate cyclase and induce small intestinal secretion; the secretory effects of heat-stable E. coli and heat-labile Shigella dysenteriae enterotoxins are not accompanied by cyclase activation. The two major complications of acute diarrhoea are (i) hypernatraemic dehydration with its attendant neurological, renal and vascular lesions, and (ii) protracted diarrhoea which may lead to severe malnutrition. Deconjugation of bile salts and colonization of the small bowel with toxigenic strains of E. coli may be important in the pathophysiology of the protracted diarrhoea syndrome. The control of bacterial diarrhoea requires a corrdinated political, educational, social, public health and scientific attack. Bacterial diarrhoea is a major health problem throughout the world, and carries an appreciable morbidity and mortality. This is particularly the case during infancy, and in those developing parts of the world where malnutrition is common. This paper is concerned mainly with acute bacterial diarrhoea, and reviews the problem as a whole.

Systematic review: prevention of travellers' diarrhoea

BACKGROUND

Renewed interest in the use of antibiotics to prevent travellers' diarrhoea has occurred with the availability of non-absorbed (<0.4%) rifaximin, and with evidence that a subgroup of travellers with diarrhoea have progression of their illnesses to postinfectious irritable bowel syndrome.

AIM

To summarize recently published information and make recommendations on travellers' diarrhoea prevention.

METHODS

PubMed was reviewed on 2 January 2008 for 255 articles on the topic of 'travellers diarrhoea' published beginning with 2000 along with the author's extensive file on prevention of travellers' diarrhoea.

RESULTS

Exercising care in food and beverage selection, while of unproven value, is recommended during travel to high-risk areas of Latin America, Southern Asia or Africa. An algorithm is presented to identify future travellers, for which chemoprophylaxis is appropriate. The preferred drug for prevention of travellers' diarrhoea is rifaximin, with bismuth subsalicylate or a fluoroquinolone also being effective. Vaccines against the principal cause of travellers' diarrhoea, enterotoxigenic Escherichia coli, are being developed.

CONCLUSIONS

Research is needed to determine the relative effectiveness of exercising care on food and beverage selection and chemoprophylaxis in preventing travellers' diarrhoea and postinfectious irritable bowel syndrome during high-risk travel. Enterotoxigenic E. coli vaccines appear to be a promising addition to travel medicine.

Genetic diversity of the gene cluster encoding longus, a type IV pilus of enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) strains produce a type IV pilus named Longus. We identified a 16-gene cluster involved in the biosynthesis of Longus that has 57 to 95% identity at the protein level to CFA/III, another type IV pilus of ETEC. Alleles of the Longus structural subunit gene lngA demonstrate a diversity of 12 to 19% at the protein level with strong positive selection for point replacements and horizontal transfer.

Treatment of travelers' diarrhea: randomized trial comparing rifaximin, rifaximin plus loperamide, and loperamide alone

BACKGROUND & AIMS

Antimotility agents provide rapid temporary relief of acute diarrhea, whereas antibiotics slowly cure the illness. Thus, the combination of an antimotility agent and an antibiotic may provide greater therapeutic benefit than either drug alone. This study evaluated the efficacy and safety of rifaximin-loperamide in the treatment of travelers' diarrhea.

METHODS

Consenting adults with acute diarrhea (> or =3 unformed stools in 24 hours with > or =1 symptom of enteric infection) were randomized to receive rifaximin 200 mg 3 times daily for 3 days; loperamide 4 mg initially followed by 2 mg after each unformed stool; or a combination of both drugs using the same dosing regimen. The primary end point was the median time from beginning therapy until passing the last unformed stool.

RESULTS

A total of 310 patients completed treatment with rifaximin (n = 102), loperamide (n = 104), or rifaximin-loperamide combination therapy (n = 104). The groups showed demographic similarity. Rifaximin and rifaximin-loperamide significantly reduced the median time until passage of the last unformed stool (32.5 +/- 4.14 h and 27.3 +/- 4.13 h, respectively) vs loperamide (69 +/- 4.11 h; P = .0019). The mean number of unformed stools passed during illness was lower with rifaximin-loperamide (3.99 +/- 4.28) compared with rifaximin (6.23 +/- 6.90; P = .004) or loperamide alone (6.72 +/- 6.93; P = .002). All treatments were well tolerated with a low incidence of adverse events.

CONCLUSIONS

Rifaximin-loperamide therapy provided rapid symptomatic improvement and greater overall wellness compared with either agent alone.

Rapid and sensitive detection of heat-labile I and heat-stable I enterotoxin genes of enterotoxigenic Escherichia coli by Loop-Mediated Isothermal Amplification

We developed a technique for detecting the heat-labile I (LTI) and heat-stable I (STI) genes of enterotoxigenic Escherichia coli (ETEC) using a novel DNA amplification procedure designated Loop-Mediated Isothermal Amplification (LAMP). The detection limit of accelerated LAMP utilizing loop primers was 4 CFU/test for LTI and was 40 CFU/test for STI, which are 10-fold higher than those of conventional PCR assay (detection limit, 40 CFU/test and 400 CFU/test, respectively). No DNA amplification was observed in LT and ST non-producing E. coli or other bacterial strains; thus, high specificity was verified. The specificity of LAMP assay was also confirmed by digestion of LAMP products using restriction enzymes and DNA sequence analysis. In the accelerated LAMP assay, DNA amplification was detected within 35 min, and thus LAMP is superior to conventional PCR in terms of rapidity. It was confirmed that increased concentrations of primers and Bst DNA polymerase could further facilitate the reaction. Furthermore, with the high amplification efficiency of the LAMP assay, amplification can be visually observed by the turbidity caused by magnesium pyrophosphate, a byproduct of the reaction. Detection of LTI and STI in ETEC by LAMP is thus an extremely rapid procedure with high sensitivity and specificity that requires no specialized equipment. This assay is expected to become a valuable tool for rapid diagnosis in ETEC infection.

Enterotoxigenic Escherichia coli colonization factor types collected from 1997 to 2001 in US military personnel during operation Bright Star in northern Egypt

Operation Bright Star (OBS) is a biennial, multinational exercise in Egypt involving 15000 US troops. Consistent with past observations in deployed troops, diarrhea is the most significant cause of morbidity. Focused efforts are ongoing to develop vaccines against the most common pathogens affecting our troops. As part of these efforts, diarrhea surveillance was conducted during OBS to monitor pathogens associated with illness and to identify new vaccine targets. A retrospective review was conducted of prior studies with similar methods. Soldiers with diarrhea presenting to the OBS clinic provided a stool sample that was inoculated into Carey-Blair transport media. Within 3 days, the Cary-Blair tubes were transported to the Naval Medical Research Unit no. 3 in Cairo where bacterial culture was performed. As part of the evaluation, 5 Escherichia coli-like colonies were collected and tested for toxin production using the GM1-ELISA. Toxin-positive isolates were further tested for colonization factors (CF) by a dot-blot assay using a standardized panel of monoclonal antibodies against CFA/I, CS1-CS7, CS17, CS8 (CFA/III), CS12 (PCFO159), and CS14 (PCFO166). Enterotoxigenic E. coli (ETEC) was the most frequently isolated pathogen during each OBS from which data were collected. The rate of ETEC-associated diarrhea ranged from 22% to 58%. Over time, there were dramatic shifts in the frequency and distribution of CFs. Over the 5 years of study, an increasing number of ETEC isolates had no known CF identified, and in 2001, only 40% of ETEC was associated with known CFs. The most commonly identified CF was CS6. Diarrheal disease, particularly ETEC, continues to be a common malady among US military personnel deployed to Egypt. We have identified ETEC CF types, especially CS6, which should be considered potential vaccine candidates. However, despite intensive testing, CFs could not be identified in most of the ETEC isolated, highlighting the need for further studies to identify novel CFs and alternative vaccine targets.

Use of probiotics in children with acute diarrhea

Probiotics, defined as microbial cell preparations or components of microbial cells that have a beneficial effect on the health and well being of the host, have traditionally been used to treat and prevent a variety of infections. Beneficial effects of probiotics in acute infectious diarrhea in children seem to be: (i) moderate; (ii) strain-dependent; (iii) dose dependent; (iv) significant in watery diarrhea and viral gastroenteritis, but non-existent in invasive, bacterial diarrhea; and (v) more evident when treatment with probiotics is initiated early in the course of disease. Three large, randomized controlled trials (RCTs) provide evidence of a very modest effect (statistically significant, but of questionable clinical importance) of some probiotic strains (Lactobaccillus GG, Lactobaccillus reuteri, Bifodobacterium lactis) on the prevention of community-acquired diarrhea. We have found conflicting evidence from four RCTs on the efficacy of Lactobacillus GG and B. bifidum and Streptococcus thermophilus in the prevention of nosocomial diarrhea in children. Two RCTs in children provide evidence of a moderate beneficial effect of Lactobacillus GG in the prevention of antibacterial-associated diarrhea (AAD), but results in adults are conflicting. Data on the efficacy of other probiotic strains in AAD in children are very limited. In conclusion, to date, the most extensively studied and best documented clinical application of probiotics in children is for the treatment of acute watery diarrhea of rotaviral or presumably viral etiology. Studies documenting effects in other types of diarrheal diseases in children are limited, although some preliminary results are promising. The effects of different probiotic microorganisms are not equal. Only very few probiotic strains have been tested rigorously in RCTs. Many questions remain to be answered. Future clinical trials should evaluate carefully selected, precisely defined probiotic strains and address clinically important endpoints.

Epidemic diarrhea due to enterotoxigenic Escherichia coli

BACKGROUND

In June 1998, we investigated one of the largest foodborne outbreaks of enterotoxigenic Escherichia coli gastroenteritis reported in the United States.

METHODS

We conducted cohort studies of 11 catered events to determine risk factors for illness. We used stool cultures, polymerase chain reaction, and serologic tests to determine the etiologic agent, and we conducted an environmental inspection to identify predisposing conditions and practices at the implicated establishment.

RESULTS

During 5-7 June, the implicated delicatessen catered 539 events attended by >16,000 people. Our epidemiological study of 11 events included a total of 612 attendees. By applying the median prevalence of illness (20%) among events with ill attendees to the total number of events with any ill attendees, we estimate that at least 3300 persons may have developed gastroenteritis during this outbreak. Multiple food items (potato salad, macaroni salad, egg salad, and watermelon) were associated with illness, all of which required extensive handling during preparation. Enterotoxigenic Escherichia coli serotype O6:H16 producing heat-labile and heat-stable toxins was isolated from the stool specimens from 11 patients. Eight patients with positive stool culture results, 11 (58%) of 19 other symptomatic attendees, and 0 (0%) of 17 control subjects had elevated serum antibody titers to E. coli O6 lipopolysaccharide. The delicatessen had inadequate hand-washing supplies, inadequate protection against back siphonage of wastewater in the potable water system, a poorly draining kitchen sink, and improper food storage and transportation practices.

CONCLUSIONS

In the United States, where enterotoxigenic Escherichia coli is an emerging cause of foodborne disease, enterotoxigenic Escherichia coli should be suspected in outbreaks of gastroenteritis when common bacterial or viral enteric pathogens are not identified.

New views on antidiarrheal effect of wood creosote: is wood creosote really a gastrointestinal antiseptic?

Wood creosote, the principal ingredient in Seirogan, has a long history as a known gastrointestinal microbicidal agent. When administered orally, the intraluminal concentration of wood creosote is not sufficiently high to achieve this microbicidal effect. Through further animal tests, we have shown that antimotility and antisecretory actions are the principal antidiarrheal effects of wood creosote. Wood creosote inhibits intestinal secretion induced by enterotoxins by blocking the Cl(-) channel on the intestinal epithelium. Wood creosote also decreases intestinal motility accelerated by mechanical, chemical, or electrical stimulus by the inhibition of the Ca(2+) influx into the smooth muscle cells. In this overview, the antimotility and antisecretory effects of wood creosote are compared with those of loperamide. Wood creosote was observed to inhibit stimulated colonic motility, but not normal jejunal motility. Loperamide inhibits normal jejunal motility, but not stimulated colonic motility. Both wood creosote and loperamide inhibit intestinal secretion accelerated by acetylcholine. Wood creosote was found to have greater antisecretory effects in the colon than loperamide. Based upon these findings, we conclude that the antidiarrheal effects of wood creosote are due to both antisecretory activity in the intestine and antimotility in the colon, but not due to the microbicidal activity as previously thought. Wood creosote was found to have no effects on normal intestinal activity. These conclusions are supported by the results of a recent clinical study comparing wood creosote and loperamide, which concluded that wood creosote was more efficacious in relieving abdominal pain and comparable to loperamide in relieving diarrhea.

Noroviruses as a cause of traveler's diarrhea among students from the United States visiting Mexico

Stool specimens from 124 international travelers with acute diarrhea were tested for the presence of enteropathogens. Noroviruses (NoVs) were the second most commonly identified enteric pathogen in diarrheal stool samples (21/124, 17%), exceeded only by enterotoxigenic Escherichia coli (50/106, 47%). This study indicates that NoV is an underappreciated cause of traveler's diarrhea.

Prophylactic Antimicrobials for Traveler's Diarrhea: An Early History

The prevention of traveler's diarrhea by use of pharmacologic agents has been of great interest since the early 1960s. It was not until the discovery of enterotoxigenic Escherichia coli as the dominant causative organism of travelers' diarrhea, however, that rational antimicrobial therapy could be studied. Selected antimicrobials have proven to be highly efficacious, but, by consensus, are not widely used.

Enterotoxigenic Escherichia coli in developing countries: epidemiology, microbiology, clinical features, treatment, and prevention

ETEC is an underrecognized but extremely important cause of diarrhea in the developing world where there is inadequate clean water and poor sanitation. It is the most frequent bacterial cause of diarrhea in children and adults living in these areas and also the most common cause of traveler's diarrhea. ETEC diarrhea is most frequently seen in children, suggesting that a protective immune response occurs with age. The pathogenesis of ETEC-induced diarrhea is similar to that of cholera and includes the production of enterotoxins and colonization factors. The clinical symptoms of ETEC infection can range from mild diarrhea to a severe cholera-like syndrome. The effective treatment of ETEC diarrhea by rehydration is similar to treatment for cholera, but antibiotics are not used routinely for treatment except in traveler's diarrhea. The frequency and characterization of ETEC on a worldwide scale are inadequate because of the difficulty in recognizing the organisms; no simple diagnostic tests are presently available. Protection strategies, as for other enteric infections, include improvements in hygiene and development of effective vaccines. Increases in antimicrobial resistance will dictate the drugs used for the treatment of traveler's diarrhea. Efforts need to be made to improve our understanding of the worldwide importance of ETEC.

Update in traveler's diarrhea

TD has not proved as preventable as hoped, despite knowing that it is transmitted mainly through food. Travelers have little ability to select restaurants based on the kitchen hygiene. The rates of TD in travelers to developing countries have not changed in the past 50 years, either because the dietary precautions they are taught are not effective or they cannot be adhered to in the course of a pleasurable vacation. Nonantibiotic prophylaxis with bismuth subsalicylate has the potential to prevent 40% to 60% of TD episodes in short-term travelers, and is probably underused. Antibiotic prophylaxis can prevent up to 90% of infections, but is not routinely recommended. Empiric treatment of TD has been the best approach to dealing with this problem, but its usefulness is being undermined by growing antibiotic resistance in many parts of the world. Fluoroquinolones are still the most useful agents where Campylobacter is not a predominant pathogen. Rifaximin may prove to be a useful addition to the options for treatment and prophylaxis. If used for treatment, it may require a backup antibiotic in areas where Campylobacter and Shigella are prominent pathogens.

Travelers' diarrhea: antimicrobial therapy and chemoprevention

The use of preventive measures and self-treatment for travelers' diarrhea is routine in regions where the occurrence of diarrhea is predictably high. People traveling to these areas who do not exercise care in their selection of consumed foods and beverages will suffer high rates of illness. Such diarrhea normally affects the traveler for a day, although it can result in chronic postinfectious irritable bowel syndrome. Although systemic antibacterial drugs are effective in preventing diarrhea, their use is not routinely recommended because of side effects and their importance as a therapy for extra-intestinal infections. This review focuses on current and future uses of antibacterial drugs in the prevention and therapy of travelers' diarrhea. Minimally absorbed (< 0.4%) rifaximin can effectively reduce the occurrence of travelers' diarrhea without side effects. Bismuth subsalicylate is a useful alternative, although it is less effective than rifaximin for the prevention of travelers' diarrhea and the required doses are less convenient. All people who travel to high-risk areas should take curative antimicrobial agents with them for self-treatment of illness: rifaximin 200 mg three times a day for 3 days, or an absorbable agent such as a fluoroquinolone or azithromycin taken in a single dose initially, with the need for a second or third dose determined by clinical response. Loperamide (up to 8 mg per day for < or = 2 days) can be given with the antibiotic to offer rapid symptomatic improvement. In the future, the ability to evaluate the genetic risk of illness acquisition might allow person-specific recommendations to be made.

Prevalence of norovirus among visitors from the United States to Mexico and Guatemala who experience traveler's diarrhea

Traveler's diarrhea (TD) is the most common infectious illness acquired by visitors to developing nations. The purpose of this study was to utilize molecular diagnostic techniques to determine the prevalence of norovirus (NoV) in TD occurring among visitors from the United States to Guatemala and Mexico. Stool samples (n = 54) were collected from 34 TD cases and analyzed for NoV by reverse transcription-PCR and oligoprobe confirmation. The overall prevalence of NoV was 65%. Interestingly, all NoV-positive stool samples were identified as genogroup I NoVs, and time spent at travel destinations was found to be an important factor in determining the frequency of infection (P = 0.003). Eleven NoV-positive stool samples also tested positive for enterotoxigenic Escherichia coli, indicating that dual infections with this leading bacterial cause of TD were very common. Results of this study suggest that NoV infection is a frequent occurrence among travelers to Mexico and Guatemala who experience episodes of TD. In addition, the simple molecular detection method utilized here will serve to facilitate more in-depth epidemiological studies of this emergent viral pathogen in travelers and other at-risk populations.

Real-time fluorescence PCR assays for detection and characterization of heat-labile I and heat-stable I enterotoxin genes from enterotoxigenic Escherichia coli

To facilitate the diagnosis of enterotoxigenic Escherichia coli (ETEC) infections in humans, we developed and evaluated real-time fluorescence PCR assays for the Roche LightCycler (LC) against the enterotoxin genes commonly present in strains associated with human illness. Separate LC-PCR assays with identical cycling conditions were designed for the type I heat-labile enterotoxin (LT I) and the type I heat-stable enterotoxin (ST I) genes, using the LC hybridization probe format. A duplex assay for ST I with two sets of amplification primers and three hybridization probes was required to detect the major nucleotide sequence variants of ST I, ST Ia and ST Ib. LC-PCR findings from the testing of 161 E. coli isolates of human origin (138 ETEC and 23 non-ETEC) were compared with those obtained by block cycler PCR analysis. The sensitivities and specificities of the LC-PCR assays were each 100% for the LT I and ST I genes. The LC-PCR and block cycler PCR assays were also compared for their abilities to detect LT I and ST I genes in spiked stool specimens with different methods of sample preparation. Findings from these experiments revealed that the limits of detection for the LC-PCR assays were the same or substantially lower than those observed for the block cycler PCR assay. Melting curve analysis of the amplified LT I and ST I genes revealed sequence variation within each gene, which for the ST I genes correlated with the presence of ST Ia and ST Ib. The rapidity, sensitivity, and specificity of the LC-PCR assays make them attractive alternatives to block cycler PCR assays for the detection and characterization of ETEC.

Inhibition of Rat Intestinal Cl– Secretion by 4,5-Dimethylresorcinol

Wood creosote, a mixture of phenolic compounds, inhibits enterotoxin-induced intestinal fluid secretion, suggesting that one of its constituents suppresses transepithelial Cl- secretion from the intestinal mucosa. To identify an active constituent in wood creosote that inhibits intestinal Cl- secretion through Cl- channels, we first examined its effect on Cl- secretion using a cultured cell line transfected with complementary DNA encoding a Cl- channel and a Cl- -sensitive fluorescent dye. We next assayed chromatographic fractions of wood creosote for the inhibitory activity on Cl- secretion using a Ussing chamber. We found that 4,5-dimethylresorcinol, identified by gas chromatography-mass spectrometry, inhibited intestinal Cl- secretion dose-dependently when added to a serosal, but not mucosal, surface of rat jejunum, a half-inhibitory concentration being 3.8 microg/ml (28 micromol/l). It was strongly suggested that this effect was due to inhibition of Cl- channels.

Enterotoxin-producing Escherichia coli O169:H41, United States

From 1996 to 2003, 16 outbreaks of enterotoxigenic Escherichia coli (ETEC) infections in the United States and on cruise ships were confirmed. E. coli serotype O169:H41 was identified in 10 outbreaks and was the only serotype in 6. This serotype was identified in 1 of 21 confirmed ETEC outbreaks before 1996.

United States male students who heavily consume alcohol in Mexico are at greater risk of travelers' diarrhea than their female counterparts

BACKGROUND

The relationship between alcohol consumption and travelers' diarrhea has not been well studied.

METHODS

A cohort of US college students (n=171), who attended 2001 or 2002 summer educational sessions in Guadalajara, Mexico, were followed prospectively to examine the frequency of alcohol consumption and the development of travelers' diarrhea.

RESULTS

More male students reported consuming >5 drinks/day of drinking while in Mexico compared to female students (p <.001). Males who consumed >5 drinks/day of drinking while in Mexico were more likely to develop diarrhea than their female counterparts who drank the same amount (79% vs. 46%; p=.035). No association was found between the development of travelers' diarrhea and the consumption of fewer than 5 drinks per day in Mexico. Non-drinkers accounted for only 8% of the population and had a relatively high attack rate of diarrhea (69%).

CONCLUSIONS

This study suggests that males who drink heavily are at high risk for developing travelers' diarrhea and may be a group of people to target for education about the moderation of use of alcohol while traveling. Nondrinkers also deserve further study in larger numbers to confirm an apparently high attack rate of diarrhea and to explore what risk factors might be involved.

Azithromycin Found to Be Comparable to Levofloxacin for the Treatment of US Travelers with Acute Diarrhea Acquired in Mexico

Increased drug resistance among enteropathogens is an emergent problem in travelers' diarrhea. This randomized, double-blind trial was conducted in Guadalajara, Mexico, during the summers of 1999-2001 to compare azithromycin with levofloxacin for the treatment of travelers' diarrhea. A total of 217 US adults were randomized to receive a single oral dose of azithromycin (1000 mg; 108 persons) or levofloxacin (500 mg; 109 persons), with a follow-up period of 4 days. Three patients in each group dropped out of the study. The median time between initiation of therapy and passage of the last unformed stool (azithromycin group, 22.3 h; levofloxacin group, 21.5 h) and the number of unformed stools passed during the 4-day follow-up period (azithromycin group, 6.5; levofloxacin group, 5.5) were similar. Treatment failure occurred in 10 patients (9.5%) receiving azithromycin and 8 patients (7.5%) receiving levofloxacin. Possible minor, self-limiting adverse events occurred in 57 patients in each treatment group. Azithromycin was found to be a safe and effective alternative to levofloxacin for the treatment of acute travelers' diarrhea in US adult travelers to Mexico.

Rifaximin versus ciprofloxacin for the treatment of traveler's diarrhea: a randomized, double-blind clinical trial

Rifaximin is a poorly absorbed rifamycin derivative under investigation for treatment of infectious diarrhea. Adult students from the United States in Mexico and international tourists in Jamaica were randomized to receive either rifaximin (400 mg twice per day) or ciprofloxacin (500 mg twice per day) for 3 days, following a double-blinded model, from June 1997 to September 1998. A total of 187 subjects with diarrhea were studied. Time from initiation of therapy to passage of last unformed stool was comparable for those receiving rifaximin or ciprofloxacin (median, 25.7 hours versus 25.0 hours, respectively). There was no significant difference in the proportion of subjects in the 2 groups with respect to clinical improvement during the first 24 hours (P=.199), failure to respond to treatment (P=.411), or microbiological cure (P=.222). The incidence of adverse events was low and similar in each group. Rifaximin is a safe and effective alternative to ciprofloxacin in the treatment of traveler's diarrhea.

Tropical diarrhoea: new developments in traveller's diarrhoea

Traveller's diarrhoea is the most common illness acquired by visitors to developing countries, affecting 20-50% of the 35 million people who travel from industrialized countries each year. Important risk factors include point of origin and destination of the traveller, host factors, and exposure to contaminated food and water. The most common causes of traveller's diarrhoea in adults in developing countries include infection with Escherichia coli, Shigella spp., Salmonella spp., Campylobacter spp., Vibrio parahaemolyticus (in Asia), rotavirus (in Latin America), and protozoa (Giardia, Cryptosporidium and Cyclospora spp., and Entamoeba histolytica). No pathogen is identified in over half of patients with traveller's diarrhoea, however. The primary objectives of treatment of traveller's diarrhoea are to reduce the symptoms and duration of diarrhoeal illness, to reduce inconvenience caused by such illness and to prevent cancellation of planned activities. These important objectives are best accomplished by empirical self-therapy with a combination of antimicrobial agents and loperamide. Since the first use of ciprofloxacin, fluoroquinolones have become the drugs of choice in empirical therapy for moderate-to-severe traveller's diarrhoea in adults. The options for children include nalidixic acid, trimethoprim-sulfamethoxazole (along with erythromycin if Campylobacter infection is a possibility) and furazolidone. Education on hygiene and safe food preparation help to prevent many diarrhoeal diseases, including traveller's diarrhoea.

Evidence base of incubation periods, periods of infectiousness and exclusion policies for the control of communicable diseases in schools and preschools

BACKGROUND

The optimal control of communicable diseases requires accurate information on incubation periods, periods of infectiousness and the effectiveness of exclusion. We collected the available evidence for a wide range of infections and infestations and produced evidence-based guidelines for their control in schools and preschools.

METHODS

A thorough MEDLINE literature search was conducted on the incubation period, period of infectiousness and effectiveness of exclusion for 41 infections. The quality of the information obtained was indicated by levels of evidence. The information was used to produce guidelines on exclusion, and the recommendations were graded according to the levels of evidence available. Grades A, B and C represented strongly, reasonably and poorly evidence-based recommendations, respectively.

RESULTS

The quality of data obtained was highly variable. Information on incubation periods was obtained for all 41 infections and was generally of good quality. Information on periods of infectiousness and effectiveness of exclusion was of a lesser quality and was found for only 11 and 4 conditions, respectively. There were 3 Grade A, 17 Grade B and 21 Grade C recommendations on exclusion. Examples of exclusion periods include: 5 days for chickenpox, measles, mumps, rubella, pertussis and scarlet fever; and 24 h from the cessation of diarrhea for most gastrointestinal diseases In contrast to existing guidelines exclusion was not recommended for school age children with hepatitis A.

CONCLUSIONS

We have been able to present the best available data on the incubation periods and periods of infectiousness of 41 childhood infections. It was possible to produce strongly or reasonably evidence-based guidelines on exclusion periods for approximately one-half of the infections.

Empirical antimicrobial therapy for traveler's diarrhea

Over 7 million cases of traveler's diarrhea, defined as the passage of > or = 3 unformed stools in a 24-h period, occur each year among visitors to developing countries. Bacterial enteric pathogens are the most common etiologic agents isolated. Preliminary clinical results for patients with diarrhea predominantly caused by Campylobacter species have shown that azithromycin may be an effective alternative to fluoroquinolones for the treatment of traveler's diarrhea.

Health problems in a large cohort of Americans traveling to developing countries

BACKGROUND

Millions of Americans visit developing countries each year, however, little is known about their health during travel. This study describes health problems in a large cohort of American travelers during and after their trip.

METHODS

A 2-year survey of 784 travelers (95% follow-up) was conducted for persons traveling for < or = 90 days. At the pretravel visit, travelers were given a postcard to record adverse health events. Following travel, standardized telephone interviews were performed for any positive responses, or if the card was not returned. All travelers were contacted 2 months after return to determine late occurring illness and compliance with antimalarials.

RESULTS

Travelers had a mean age of 44 years, a median duration of 19 days, and visited 123 countries. An illness was reported by 64% (1.6 illnesses per traveler). Ill travelers were more often female, and traveled longer than those who were not ill; depending upon destination, each day of travel increased by 3 to 4% the chance of becoming ill. Diarrhea was most common, occurring in 46%; 34% met a strict definition for traveler's diarrhea. Respiratory illness occurred in 26%, skin disorders in 8%, acute mountain sickness in 6%, motion sickness in 5%, accidents and injuries in 5%, and isolated febrile episodes in 3%. Medical care was sought by 8% of all travelers and 12% of those reporting illness. On return, 26% of travelers were ill, 56% of whom became ill after return. Diarrhea, respiratory illness, skin disorders, and febrile syndromes were most common, and 46% of those who were ill sought medical care. Complete compliance with antimalarials was 80%. Noncompliant individuals usually discontinued medications on return. Side effects were reported by 4% of those taking chloroquine, 11% of those taking chloroquine plus proguanil, and 14% of those taking mefloquine, with half of these neuropsychiatric. The incidence of documented malaria was 3.8 cases per 1,000 travelers.

CONCLUSIONS

Many travelers experience adverse health events during and after travel to the developing world. Attention to the prevention and therapy of traveler's diarrhea, prophylaxis of malaria, management of respiratory illness, personal safety, and access to medical care during travel, and, recognition of clinical syndromes after return, will help to improve the traveler's health.

Quinolone resistance in enterotoxigenic Escherichia coli causing diarrhea in travelers to India in comparison with other geographical areas

Enterotoxigenic Escherichia coli isolates were identified as a cause of traveler's diarrhea in 82 of 520 (16%) patients and tested for resistance to seven antimicrobial agents. Thirty patients (36%) needed antimicrobial therapy: 17 (56%) for persistence of symptoms and 13 (44%) for severity of symptoms. Ampicillin, tetracycline, and trimethoprim-sulfamethoxazole resistance was high. Chloramphenicol showed moderate activity, and amoxicillin plus clavulanic acid, nalidixic acid, and ciprofloxacin showed very good activity. Five nalidixic acid-resistant strains were isolated, four from patients visiting India.

Antibiotic treatment for travellers' diarrhoea

BACKGROUND

Traveller's diarrhoea is a syndrome frequently encountered in persons crossing an international boundary. Diarrhoea can lead to significant discomfort and interference with travel plans. Bacterial pathogens are a frequent cause of this syndrome. Several antibiotics have been tested for efficacy in reducing the duration and severity of the illness.

OBJECTIVES

The aims of this review were to assess the effects of antibiotics on traveller's diarrhoea in relation to duration of illness, severity of illness, and adverse effects of medications.

SEARCH STRATEGY

The Cochrane Collaboration Trials Register, MEDLINE, and EMBASE were searched. Additional trials were identified by hand searching. Content experts were contacted.

SELECTION CRITERIA

All trials in any language in which travellers older than 5 years were randomly allocated to treatment for acute non-bloody diarrhoea with antibiotics and where the causative organism is not known at allocation.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trial quality and extracted data.

MAIN RESULTS

Twenty published studies met inclusion and quality criteria for inclusion. Twelve studies were placebo-controlled. A meta-analysis for the primary outcome was not feasible. All of the 10 trials reported a significant reduction in duration of diarrhoea in participants treated with antibiotics compared with placebo. Data from two trials demonstrated a small reduction for antibiotic treated patients in the number of unformed stools passed per each 24 hour period from randomisation up to 72 hours. Data from six trials demonstrated a greater number of participants being cured of diarrhoea by 72 hours (odds ratio [OR] 5. 9, 95% confidence interval [CI] 4.06 to 8.57). Data regarding side effects were available from five trials. There was wide variation in the prevalence of side effects reported in different trials. Persons taking antibiotics experienced more side effects than those taking placebo (OR 2.37, 95% CI 1.5 to 3.75).

REVIEWER'S CONCLUSIONS

Antibiotic treatment is associated with shorter duration of diarrhoea but higher incidence of side-effects. Trials generally do not report duration of post-treatment diarrhoea using time-to-event analyses, and should do.