Enterotoxigenic Escherichia coli as cause of diarrhea among Mexican adults and US travelers in Mexico

Evaluation of the immunogenicity and protective efficacy of a recombinant CS6-based ETEC vaccine in an Aotus nancymaae CS6 + ETEC challenge model

Colonization factors or Coli surface antigens (CFs or CS) are important virulence factors of Enterotoxigenic E. coli (ETEC) that mediate intestinal colonization and accordingly are targets of vaccine development efforts. CS6 is a highly prevalent CF associated with symptomatic ETEC infection both in endemic populations and amongst travelers. In this study, we used an Aotus nancymaae non-human primate ETEC challenge model with a CS6 + ETEC strain, B7A, to test the immunogenicity and protective efficacy (PE) of a recombinant CS6-based subunit vaccine. Specifically, we determined the ability of dscCssBA, the donor strand complemented recombinant stabilized fusion of the two subunits of the CS6 fimbriae, CssA and CssB, to elicit protection against CS6 + ETEC mediated diarrhea when given intradermally (ID) with the genetically attenuated double mutant heat-labile enterotoxin LT(R192G/L211A) (dmLT). ID vaccination with dscCssBA + dmLT induced strong serum antibody responses against CS6 and LT. Importantly, vaccination with dscCssBA + dmLT resulted in no observed diarrheal disease (PE = 100%, p = 0.03) following B7A challenge as compared to PBS immunized animals, with an attack rate of 62.5%. These data demonstrate the potential role that CS6 may play in ETEC infection and that recombinant dscCssBA antigen can provide protection against challenge with the homologous CS6 + ETEC strain, B7A, in the Aotus nancymaae diarrheal challenge model. Combined, these data indicate that CS6, and more specifically, a recombinant engineered derivative should be considered for further clinical development.

Clinical aspects of heat-labile and heat-stable toxin-producing enterotoxigenic Escherichia coli: A prospective study among Finnish travellers

BACKGROUND

Enterotoxigenic Escherichia coli (ETEC) is a major pathogen causing travellers' diarrhoea (TD) among visitors to low- and middle-income countries (LMIC). Scant data are available on rates of travel-acquired ETEC producing heat-labile (LT) and/or heat-stable (ST) toxin or its subtypes, STh (human) and STp (porcine) in various geographic regions, and on clinical pictures associated with each toxin.

METHODS

Using qPCR, we analysed LT, STh, and STp in stools positive for ETEC in a prospective study among 103 Finnish travellers visiting LMIC. They filled in questionnaires and provided stool samples before and after travel. We scrutinized geographic distribution of LT, STh, and STp ETEC findings, and association between these different ETEC subtypes and moderate/severe TD.

RESULTS

Among the 103 stool samples positive for ETEC toxins, the rate for LT was 76%, for STh 26%, and STp 41%. The rate for LT-only was 44%, for STh-only 6%, STp-only 16%, LT + STh 10%, LT + STp 15%, STh + STp 3%, and LT + STh + STp 8%. Findings varied by destination; the rates of LT, STh, and STp were 79%, 21%, and 57%, respectively, in Southern Asia (n = 14); 85%, 10%, and 20% in South-eastern Asia (n = 20); 84%, 13%, and 29% in Eastern Africa (n = 31); and 56%, 50%, and 63% in Western Africa (n = 32), respectively. Of travellers positive for LT, STh, and STp, 83%, 100%, and 88%, encountered TD; 35%, 55%, and 41% reported moderate/severe TD. STh was associated with moderate/severe TD.

CONCLUSIONS

Toxin findings varied by destination; multiple toxins were commonly detected. Moderate/severe TD was reported most frequently by subjects with STh-ETEC.

GABA attenuates ETEC-induced intestinal epithelial cell apoptosis involving GABAAR signaling and the AMPK-autophagy pathway

Enterotoxigenic Escherichia coli (ETEC) triggers diarrhea in humans and livestock. We have previously showed that ETEC promotes intestinal epithelial cell apoptosis and increases gamma-aminobutyric acid (GABA) concentration in the jejunum, suggesting that GABA might mediate ETEC-induced apoptosis. Here, we found that GABA alleviates ETEC-induced intestinal barrier dysfunctions, including ETEC-induced apoptosis both in vivo and in vitro. Interestingly, the alleviation of GABA on ETEC-induced apoptosis largely depends on autophagy. Mechanistically, GABA attenuates ETEC-induced apoptosis via activating GABA_AR signaling and the AMPK-autophagy pathway. These findings highlight that maintaining intestinal GABA concentration could alleviate intestinal ETEC infection.

Enterotoxigenic Escherichia coli heat labile enterotoxin inhibits intestinal ascorbic acid uptake via a cAMP-dependent NF-κB-mediated pathway

Vitamin C is an antioxidant and acts as a cofactor for many enzymatic reactions. Humans obtain vitamin C from dietary sources via intestinal absorption, a process that involves the sodium-dependent vitamin C transporters-1 and -2 (SVCT1 and SVCT2). Enterotoxigenic Escherichia coli (ETEC) infection impacts intestinal absorption/secretory functions, but nothing is known about its effect on ascorbic acid (AA) uptake. Here we demonstrate that infection of Caco-2 cells with ETEC led to a significant inhibition in intestinal AA uptake. This inhibition was associated with a marked reduction in hSVCT1 and hSVCT2 protein, mRNA, and heterogeneous nuclear RNA (hnRNA) expression levels as well as significant inhibition in the activity of both the SLC23A1 and SLC23A2 promoters. Similarly, exposure of mice to ETEC led to a significant inhibition in intestinal AA uptake and reduction in mSVCT1 and mSVCT2 protein, mRNA, and hnRNA expression levels. Inhibition was caused by the action of heat labile enterotoxin (LT), since infecting Caco-2 cells with LT-deficient ETEC (ΔLT) failed to impact AA uptake. Because LT activates adenylate cyclase, we also examined the effect of dibutyryl-cAMP in AA uptake by Caco-2 cells and observed a significant inhibition. Furthermore, treating the cells with celastrol, a specific NF-κB inhibitor, significantly blocked the inhibition of AA uptake caused by ETEC infection. Together, these data demonstrate that ETEC infection impairs intestinal AA uptake through a cAMP-dependent NF-κB-mediated pathway that regulates both SLC23A1 and SLC23A2 transcription. NEW & NOTEWORTHY Our findings demonstrate that heat-labile enterotoxin produced by enterotoxigenic Escherichia coli inhibits AA uptake in intestinal epithelial cells and mouse intestine. This effect is mediated through transcriptional repression of SLC23A1 (SVCT1) and SLC23A2 (SVCT2) via a cAMP-dependent NF-κB signaling pathway.

Comparison of Two Forms of Loperamide-Simeticone and a Probiotic Yeast (Saccharomyces boulardii) in the Treatment of Acute Diarrhoea in Adults: A Randomised Non-Inferiority Clinical Trial

BACKGROUND

Acute diarrhoea is a frequent health problem in both travellers and residents that has a social and economic impact. This study compared the efficacy and tolerability of two loperamide-simeticone formulations and a Saccharomyces boulardii capsule as symptomatic treatment.

METHODS

This was a prospective, randomised, single (investigator)-blind, three-arm, parallel group, non-inferiority clinical trial in adult subjects with acute diarrhoea at clinics in Mexico and India, with allocation to a loperamide-simeticone 2/125 mg caplet or chewable tablet (maximum eight in 48 h) or S. boulardii (250 mg twice daily for 5 days).

OUTCOME MEASURES

The primary outcome measure was the number of unformed stools between 0 and 24 h following the initial dose of study medication (NUS 0-24). The secondary outcome measures were time to last unformed stool (TLUS), time to complete relief of diarrhoea (TCRD), time to complete relief of abdominal discomfort (TCRAD) and the subject's evaluation of treatment effectiveness. Follow-up endpoints at 7 days were feeling of complete wellness; stool passed since final study visit; and continued or recurrent diarrhoea.

SUBJECTS

In this study, 415 subjects were randomised to either a loperamide-simeticone caplet (n = 139), loperamide-simeticone chewable tablet (n = 139) or S. boulardii capsule (n = 137) and were included in the intention-to-treat analysis.

RESULTS

With regards to mean NUS 0-24, the loperamide-simeticone caplet was non-inferior to loperamide-simeticone tablets (3.4 vs. 3.3; one-sided 97.5 % confidence interval ≤0.5), with both significantly lower than S. boulardii (4.3; p < 0.001). The loperamide-simeticone groups had a shorter median TLUS [14.9 and 14.0 vs. 28.5 h (loperamide-simeticone caplet and chewable tablet groups, respectively, vs. S. boulardii); p < 0.001], TCRD (26.0 and 26.0 vs. 45.8 h; p < 0.001) and TCRAD (12.2 and 12.0 vs. 23.9 h; p < 0.005) than S. boulardii. Treatment effectiveness for overall illness, diarrhoea and abdominal discomfort relief was greater (p < 0.001) in the loperamide-simeticone groups than with S. boulardii. At 7-day follow-up most subjects reported passing stool at least once since the final study visit (loperamide-simeticone caplet 94.1 %, loperamide-simeticone chewable tablet 94.8 %, S. boulardii 97.0 %), did not experience continued or recurrent diarrhoea [loperamide-simeticone caplet 3.7 % (p < 0.03 vs. S. boulardii), loperamide-simeticone chewable tablet 3.7 %, S. boulardii 5.7 %] and felt completely well [loperamide-simeticone caplet 96.3 % (p < 0.02 vs. S. boulardii), loperamide-simeticone chewable tablet 96.3 % (p < 0.02 vs. S. boulardii), S. boulardii 88.6 %]. All treatments were well-tolerated with few adverse events.

CONCLUSIONS

The loperamide-simeticone caplet was non-inferior to the original loperamide-simeticone chewable tablet formulation; both formulations can be expected to demonstrate similar clinical efficacy in the relief of symptoms of acute diarrhoea. Both loperamide-simeticone formulations were superior to the S. boulardii capsule in the primary and secondary endpoints.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00807326.

Enterotoxigenic Escherichia coli infection and intestinal thiamin uptake: studies with intestinal epithelial Caco-2 monolayers

Infections with enteric pathogens like enterotoxigenic Escherichia coli (ETEC) is a major health issue worldwide and while diarrhea is the major problem, prolonged, severe, and dual infections with multiple pathogens may also compromise the nutritional status of the infected individuals. There is almost nothing currently known about the effect of ETEC infection on intestinal absorptions of water-soluble vitamins including thiamin. We examined the effect of ETEC infection on intestinal uptake of the thiamin using as a model the human-derived intestinal epithelial Caco-2 cells. The results showed that infecting confluent Caco-2 monolayers with live ETEC (but not with boiled/killed ETEC or nonpathogenic E. coli) or treatment with bacterial culture supernatant led to a significant inhibition in thiamin uptake. This inhibition appears to be caused by a heat-labile and -secreted ETEC component and is mediated via activation of the epithelial adenylate cyclase system. The inhibition in thiamin uptake by ETEC was associated with a significant reduction in expression of human thiamin transporter-1 and -2 (hTHTR1 and hTHTR2) at the protein and mRNA levels as well as in the activity of the SLC19A2 and SLC19A3 promoters. Dual infection of Caco-2 cells with ETEC and EPEC (enteropathogenic E. coli) led to compounded inhibition in intestinal thiamin uptake. These results show for the first time that infection of human intestinal epithelial cells with ETEC causes a significant inhibition in intestinal thiamin uptake. This inhibition is mediated by a secreted heat-labile toxin and is associated with a decrease in the expression of intestinal thiamin transporters.

Prevalence and antibiotic resistance profiles of diarrheagenic Escherichia coli strains isolated from food items in northwestern Mexico

Diarrheogenic Escherichia coli (DEC) strains are an important cause of intestinal syndromes in the developing world mainly affecting children. DEC strains often infect tourists from developed countries traveling to Mexico, causing so-called "traveler diarrhea". DEC strains are typically transmitted by contaminated food and water; however, the prevalence of these strains in food items that are produced, consumed and sometimes exported in northwestern Mexico has not been evaluated. In this study, we conducted a large microbiological survey of DEC strains in 5162 food items and beverages consumed throughout Sinaloa state during 2008 and 2009. We developed a panel of eight sequential PCR reactions that detected the presence of all DEC categories, including typical or atypical variants. Thermotolerant coliforms (also known as fecal coliforms) and E. coli were detected by conventional bacteriology in 13.4% (692/5162) and 7.92% (409/5162) of food items, respectively. Among 409 E. coli isolates, 13.6% (56/409) belonged to DEC strains. Dairy products (2.8%) were the most contaminated with DEC, while DEC strains were not detected in beverages and ice samples. The pathogenic type that was most commonly isolated was EPEC (78.5%), followed by EAEC (10.7%), STEC (8.9%) and ETEC (1.7%). EHEC, DAEC and EIEC strains were not detected. Approximately 80% of EPEC and EAEC strains were classified as atypical variants; they did not adhere to a culture of HEp-2 cell. Of the isolated DEC strains, 66% showed resistance to at least one commonly prescribed antibiotic. In conclusion, the presence of DEC strains in food items and beverages available in northwestern Mexico is low and may not represent a threat for the general population or those traveling to tourist areas.

C57-CD40 ligand deficient mice: a potential model for enterotoxigenic Escherichia coli (H10407) colonization

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrheal disease in humans, calves and pigs. In humans, these infections mainly occur in developing countries leading to a high diarrheal morbidity and infant mortality and to travellers' diarrhea. ETEC strains constitute a phenotypically and genetically diverse pathotype with as common characteristics the production of heat-labile (LT) and/or heat-stable enterotoxins (ST) as well as of one or more fimbrial colonization factors. Despite the global importance of these pathogens, a broadly ETEC protective vaccine is not yet available, partially due to the lack of a suitable animal model for human ETEC. Such model would allow to test more ETEC molecules as potential vaccine candidates. The C57-CD40 ligand deficient (C57-cd40l(-/-)) mouse has been successfully used to develop infection models of intestinal pathogens, but little is known about its humoral immune response. Therefore, the aims of this study were to characterize the humoral immune response of C57 and C57-cd40l(-/-) mice and to determine the persistence of ETEC H10407 and two of its variants after oral inoculation. The serum IgM, IgG and IgA and faecal IgG and IgA concentrations, of twelve mice per mouse strain (C57 and C57-cd40l(-/-)), were determined by ELISA. All serum immunoglobulins and the faecal IgG concentration were significantly lower in C57-cd40l(-/-) than in C57 mice. In contrast the faecal IgA concentration was significantly higher in the C57-cd40l(-/-) mice. This high intestinal IgA concentration might be a compensatory T cell-independent production of IgA production. Both mouse strains were orally inoculated with 5×10(8) ETEC H10407 (LT(+), ST-colonization factor antigen I (CFA/I)(+)) and ETEC in animal faeces was established by culture followed by st and lt loci identification by PCR until day 14 post infection. Most C57 mice eliminated the strain within 3 days whereas infection remained in C57-cd40l(-/-) mice until day 14. Subsequently both mouse strains were inoculated with ETEC H10407 variants and followed up until day 113. Likewise C57 mice eliminated both ETEC variants within 4 days. All C57-cd40l(-/-) mice had eliminated the LT(-) variant at day 31, whereas the ST-CFA/I(-) variant remained in mice stools until day 113. These observations suggest that C57-cd40l(-/-) mice are permissive for ETEC H10407 colonization.

Escherichia coli pathotypes in Pakistan from consecutive floods in 2010 and 2011

This study compares Escherichia coli pathotypes circulating among children in Pakistan during the floods of 2010 and 2011 and from sporadic cases outside flood affected areas. Using multiplex polymerase chain reaction 115 of 205 stool samples (56.29%) were positive for diarrheagenic E. coli from specimens taken during the floods compared with 50 of 400 (12.5%) stool samples being positive for sporadic cases. The E. coli pathotypes were categorized as Enteropathogenic E. coli 33 (28.69%) and 13 (26%), Enterotoxigenic E. coli 29 (25.21%) and 15 (30%), Enteroaggregative E. coli 21 (18.2%) and 18 (36%), Enterohemorrhagic E. coli 5 (4.34%) and 1 (2%) from flood and sporadic cases, respectively. Furthermore, patients co-infected with more than one pathotype were 26 (22.60%) and 3 (6%) from flood and sporadic cases, respectively. The study shows an unexpectedly high rate of isolation of E. coli pathotypes suggesting Pakistan as an endemic region that requires active surveillance particularly during flood periods.

Involvement of quorum sensing and heat-stable enterotoxin a in cell damage caused by a porcine enterotoxigenic Escherichia coli strain

Enterotoxigenic Escherichia coli (ETEC) strains with K88 fimbriae are often associated with the outbreaks of diarrhea in newborn and weaned piglets worldwide. In the present study, we observed that 10⁸ CFU/ml of K88(+) ETEC strain JG280 caused more death of pig intestinal IPEC-J2 cells than did 10⁹ CFU/ml, suggesting that ETEC-induced cell death was cell density dependent and that quorum sensing (QS) may play a role in pathogenesis. Subsequent investigations demonstrated a positive correlation between autoinducer 2 (AI-2) activity of JG280 and death of IPEC-J2 cells during the infection for up to 3 h. However, there was a negative correlation between AI-2 activity and expression of the JG280 enterotoxin genes estA and estB when IPEC-J2 cells were exposed to the pathogen at 10⁸ CFU/ml. We therefore cloned the luxS gene (responsible for AI-2 production) from JG280 and overexpressed it in E. coli DH5α, because deletion of the luxS gene was retarded by the lack of suitable antibiotic selection markers and the resistance of this pathogen to a wide range of antibiotics. The addition of culture fluid from E. coli DH5α with the overexpressed luxS reduced cell death of IPEC-J2 cells by 10⁸ CFU/ml JG280. The addition also reduced the estA expression by JG280. Nonpathogenic K88(+) strain JFF4, which lacks the enterotoxin genes, caused no death of IPEC-J2 cells, although it produced AI-2 activity comparable to that produced by JG280. These results suggest the involvement of AI-2-mediated quorum sensing in K88(+) ETEC pathogenesis, possibly through a negative regulation of STa production.

Clinical characteristics and etiology of travelers' diarrhea among Korean travelers visiting South-East Asia

The morbidity of travelers' diarrhea (TD) is still high. This study examined the incidence of common pathogens and characteristics of TD among Korean travelers who visited South-East Asian countries. We performed a prospective study involving 479 Korean travelers with diarrheal disease from February 2009 to April 2009 and stool samples were examined and questionnaire surveys were done after arrival. Enterotoxigenic Escherichia coli (ETEC) was found in 36.0% of TD cases, as were the following: Enteroaggregative Escherichia coli (EAEC) in 27.0%, Vibrio parahaemolyticus in 13.1%, and Norovirus in 11.5%. The detected rate of classic TD was higher in men (P = 0.007), in patients who had a shorter duration trip (P = 0.023) and in patients who drank more than 1 liter of water per day (P = 0.037). Positive stool culture rates were higher in men (P = 0.005), in hospitalized patients (P = 0.013). and in those who consumed impure water or raw foods (P = 0.033). A higher severity of disease corresponded to a significantly higher culture positivity rate (P = 0.029). We should consider the possibility of other pathogens in addition to ETEC in patients with TD who visit South-East Asia. Travelers need to educate about risk factors associated with TD.

Diagnosis and treatment of acute or persistent diarrhea

Studies of microbial pathogens and the toxins they produce are important for determining the mechanisms by which they cause disease and spread throughout a population. Some bacteria produce secretory enterotoxins (such as cholera toxin or the heat-labile or stable enterotoxins produced by Escherichia coli) that invade cells directly. Others invade cells or produce cytotoxins (such as those produced by Shigella, enteroinvasive E coli, or Clostridium difficile) that damage cells or trigger host responses that cause small or large bowel diseases (such as enteroaggregative or enteropathogenic E coli or Salmonella). Viruses (such as noroviruses and rotaviruses) and protozoa (such as Cryptosporidium, Giardia, or Entamoeba histolytica) disrupt cell functions and cause short- or long-term disease. Much epidemiologic data about these pathogens have been collected from community- and hospital-acquired settings, as well as from patients with traveler's or persistent diarrhea. These studies have led to practical approaches for prevention, diagnosis, and treatment.

Cost-benefit of WC/rBS oral cholera vaccine for vaccination against ETEC-caused travelers' diarrhea

BACKGROUND

The most common infectious health problem encountered by travelers to countries in the developing region is travelers' diarrhea (TD), with enterotoxigenic Escherichia coli (ETEC) being the most common pathogen isolated. Although mild in most cases, the disease still leads to the loss of a significant part of a vacation or business trip. There is currently a lack of knowledge about the costs in relation to the benefits of vaccination against TD caused by ETEC, and the purposes of this study were to estimate and develop a cost-benefit analysis of vaccination using whole-cell/recombinant-B-subunit oral cholera vaccine.

METHODS

The consequences of the vaccination were identified and quantified in monetary terms. The cost-benefits for leisure and business travelers were assessed separately. The value of the travel was separated into the cost of the trip and of lost leisure time/business opportunities. A person with TD was in base case estimated to lose on average 3.5 days of a 7-day leisure trip and 2.5 days of a 4-day business trip. Results are presented for a Canadian traveler to endemic areas in year 2007 in US$.

RESULTS

The average cost of a TD event was estimated at $1,460 and $1,996 for leisure and business travelers, respectively. The net value of the vaccination, however, varied with the risk of the disease. Through extensive literature searches, an updated ETEC map illustrating the proportion of ETEC-caused TD was created.

CONCLUSIONS

The analysis indicated that vaccination would be considered cost-effective at incidence rates of ETEC-caused TD above about 13 and 9% for leisure and business travelers, respectively. It is, however, important to keep in mind that it is the value of the travel for the individual traveler that will decide if the vaccination provides good value for money.

Association of diarrheagenic Escherichia coli Pathotypes with infection and diarrhea among Mexican children and association of atypical Enteropathogenic E. coli with acute diarrhea

Seventy-six children < or =2 years old were prospectively followed for 1 year in a peri-urban community of Mexico City to determine asymptomatic infection and acute diarrhea associated with diarrheagenic Escherichia coli pathotypes (DEPs). By use of a pathogen-specific multiplex PCR, DEPs were sought in 795 stool samples, of which 125 (16%) were positive for DEP; of these, 4 represented shedding episodes and 4 parasite coinfections. Most single-DEP infections (85/117) were asymptomatic (P < 0.001), and of the 32 DEP diarrhea episodes, 41% were associated with atypical enteropathogenic E. coli (aEPEC), 37.5% with enterotoxigenic E. coli, 9% with typical EPEC, 9% with enteroinvasive E. coli, and 3% with Shiga toxin-producing E. coli strains. Among the 76 children, 54 had at least one stool positive for DEP, of which 23 experienced a DEP-associated diarrhea episode. In the last group of children, DEP infection was significantly associated with a diarrhea episode (relative risk [RR] = 2.5; 95% confidence interval [CI], 1.79 to 3.57; P < 0.001), with ETEC (RR = 2.30; 95% CI, 1.49 to 3.54; P = 0.003) and aEPEC (RR = 1.92; 95% CI, 1.23 to 3.0; P = 0.019) being the pathotypes associated with diarrhea. aEPEC-associated diarrhea episodes were frequently in the <12-month age group (RR = 2.57; 95% CI, 1.05 to 6.27; P = 0.04). aEPEC infections were distributed all year round, but associated diarrheal episodes were identified from April to October, with a May-June peak (rainy season). Most ETEC infections and diarrhea episodes characteristically occurred during the summer (rainy season), with a diarrhea peak in August. Of all DEPs, only aEPEC was associated with acute diarrhea episodes lasting 7 to 12 days (P = 0.019). DEPs are important causes of community-acquired enteric infection and diarrhea in Mexican children.

Influence of host interleukin-10 polymorphisms on development of traveler's diarrhea due to heat-labile enterotoxin-producing Escherichia coli in travelers from the United States who are visiting Mexico

Up to 60% of U.S. visitors to Mexico develop traveler's diarrhea (TD), mostly due to enterotoxigenic Escherichia coli (ETEC) strains that produce heat-labile (LT) and/or heat-stable (ST) enterotoxins. Distinct single-nucleotide polymorphisms (SNPs) within the interleukin-10 (IL-10) promoter have been associated with high, intermediate, or low production of IL-10. We conducted a prospective study to investigate the association of SNPs in the IL-10 promoter and the occurrence of TD in ETEC LT-exposed travelers. Sera from U.S. travelers to Mexico collected on arrival and departure were studied for ETEC LT seroconversion by using cholera toxin as the antigen. Pyrosequencing was performed to genotype IL-10 SNPs. Stools from subjects who developed diarrhea were also studied for other enteropathogens. One hundred twenty-one of 569 (21.3%) travelers seroconverted to ETEC LT, and among them 75 (62%) developed diarrhea. Symptomatic seroconversion was more commonly seen in subjects who carried a genotype producing high levels of IL-10; it was seen in 83% of subjects with the GG genotype versus 54% of subjects with the AA genotype at IL-10 gene position -1082 (P, 0.02), in 71% of those with the CC genotype versus 33% of those with the TT genotype at position -819 (P, 0.005), and in 71% of those with the CC genotype versus 38% of those with the AA genotype at position -592 (P, 0.02). Travelers with the GCC haplotype were more likely to have symptomatic seroconversion than those with the ATA haplotype (71% versus 38%; P, 0.002). Travelers genetically predisposed to produce high levels of IL-10 were more likely to experience symptomatic ETEC TD.

Use of a patch containing heat-labile toxin from Escherichia coli against travellers' diarrhoea: a phase II, randomised, double-blind, placebo-controlled field trial

BACKGROUND

Enterotoxigenic Escherichia coli (ETEC) is a major cause of travellers' diarrhoea. We investigated the rate of diarrhoea attacks, safety, and feasibility of a vaccine containing heat-labile enterotoxin (LT) from ETEC delivered to the skin by patch in travellers to Mexico and Guatemala.

METHODS

In this phase II study, healthy adults (aged 18-64 years) who planned to travel to Mexico or Guatemala and had access to a US regional vaccination centre were eligible. A centralised randomisation code was used for allocation, which was masked to participants and site staff. Primary endpoints were to investigate the field rate of ETEC diarrhoea, and to assess the safety of heat-labile toxins from E coli (LT) delivered via patch. Secondary endpoints included vaccine efficacy against travellers' diarrhoea and ETEC. Participants were vaccinated before travel, with two patches given 2-3 weeks apart. Patches contained either 37.5 mug of LT or placebo. Participants tracked stool output on diary cards in country and provided samples for pathogen identification if diarrhoea occurred. Diarrhoea was graded by the number of loose stools in 24 h: mild (three), moderate (four or five), and severe (at least six). Analysis was per protocol. The trial is registered with ClinicalTrials.gov, number NCT00516659.

FINDINGS

Recruitment closed after 201 participants were assigned patches. 178 individuals received two vaccinations and travelled and 170 were analysed. 24 (22%) of 111 placebo recipients had diarrhoea, of whom 11 (10%) had ETEC diarrhoea. The vaccine was safe and immunogenic. The 59 LT-patch recipients were protected against moderate-to-severe diarrhoea (protective efficacy [PE] 75%, p=0.0070) and severe diarrhoea (PE 84%, p=0.0332). LT-patch recipients who became ill had shorter episodes of diarrhoea (0.5 days vs 2.1 days, p=0.0006) with fewer loose stools (3.7 vs 10.5, p<0.0001) than placebo.

INTERPRETATION

Travellers' diarrhoea is a common ailment, with ETEC diarrhoea illness occurring in 10% of cases. The vaccine patch is safe and feasible, with benefits to the rate and severity of travellers' diarrhoea.

Enterotoxigenic Escherichia coli (ETEC): a recurring decimal in infants' and travelers' diarrhea

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea in infants and in travelers from developed to underdeveloped countries, especially in regions of poor sanitation. The ETEC are acquired by the ingestion of contaminated food and water, and adults living in endemic areas develop immunity. The disease condition manifests as a minor discomfort to a severe cholera-like syndrome and requires colonization by the microorganism and the elaboration of one or more enterotoxins. The ETEC attach to the epithelial cells of the gastrointestinal tract and release substances that affect the normal functioning of the tract, thereby resulting in diarrhea, and subsequently millions of deaths everyday, particularly in children. The prevention of the spread of this strain of diarrheagenic E. coli depends on ensuring appropriate sanitary measures; hand-washing and proper preparation of food; chlorination of water supplies; and appropriate sewage treatment and disposal. Parenteral or oral fluid and electrolyte replacement is used to prevent dehydration, and broad-spectrum antibiotics are used in chronic or life-threatening cases, but in most cases, should be avoided because of severe side effects.

The EtpA exoprotein of enterotoxigenic Escherichia coli promotes intestinal colonization and is a protective antigen in an experimental model of murine infection

The enterotoxigenic Escherichia coli (ETEC) strains are major causes of morbidity and mortality due to diarrheal illness in developing countries. At present, there is no broadly protective vaccine for this diverse group of pathogens. The EtpA protein, identified in ETEC H10407 in a recent search for candidate immunogens, is a large glycosylated exoprotein secreted via two-partner secretion (TPS). Similar to structurally related molecules, EtpA functions in vitro as an adhesin. The studies reported here use a recently developed murine model of ETEC intestinal colonization to examine the immunogenicity and protective efficacy of EtpA. We report that mice repeatedly exposed to ETEC are protected from subsequent colonization and that they mount immune responses to both EtpA and its presumed two-partner secretion transporter (EtpB) during the course of experimental infection. Furthermore, isogenic etpA deletion mutants were impaired in the colonization of mice, and intranasal immunization of mice with recombinant EtpA conferred protection against ETEC H10407 in this model. Together, these data suggest that EtpA is required for optimal colonization of the intestine, findings paralleling those of previous in vitro studies demonstrating its role in adherence. EtpA and other TPS proteins may be viable targets for ETEC vaccine development.

Travelers' knowledge of prevention and treatment of travelers' diarrhea

BACKGROUND

Information regarding the prevention and treatment of travelers' diarrhea (TD) is available to the public from various sources, such as medical personnel, travel clinics, personal contacts, and the Internet. This type of information may help travelers avoid this illness or help those afflicted minimize its duration.

METHODS

We collected questionnaire data from 104 travelers at departure gates for flights to Mexico from Calgary, Alberta on their knowledge of symptoms and treatment of TD and food risks associated with this illness and sources of information used.

RESULTS

Almost half reported they received some information on travel-related diseases and on TD prior to the flight. When education level was controlled for, the mean score for people who had obtained information on TD was significantly higher than that for those who did not have such information. College or university-educated travelers scored better than did other travelers. A high proportion of travelers correctly identified risk levels associated with specific foods consumed during travel, and many recognize that they are at an increased risk of acquiring diarrheal illness while traveling in a developing country.

CONCLUSIONS

Information on TD appears to improve the level of knowledge on its prevention and treatment among travelers from southern Alberta.

Behaviors and perceptions of Japanese tourists affecting diarrheal illness and health care need assessment: A questionnaire study

Objectives

To measure the prevalence rate of, and determine the association between food and drink related behaviors and diarrheal illness among Japanese tourists, and assess their health care needs.

Methods

Eligible Japanese tourists (1,480) aged ≥15 years traveling in Chiangmai Province in the north, Ayutthaya Province in the center, Kanchanaburi Province in the west, Pattaya City in the east, and Krabi Province in the south of Thailand were enrolled in the study. Of these tourists, 1,318 consented to participate in this study and completed questionnaires in Japanese, giving a response rate of 89.1%.

Results

Among these Japanese tourists 21.3% had diarrheal illness, and of these tourists, 5.0% had classical travelers’ diarrhea (TD), 11.8% had mild TD, 3.3% had good food and drink related behaviors, and 75.4% had moderate level of perception of diarrhea related to drinking and eating. Multiple logistic regression analysis indicated three significant diarrheal illness predictors: large number of previous visits to Thailand, longer stay in Thailand, and the experience of visiting other countries. Furthermore, 56.9% suggested providing an adequate number of toilets at tourist destinations; 53.9% suggested providing a 24-hour emergency call facility for a public ambulance; and 51.9% suggested providing garbage bins and garbage disposal facilities at tourist destinations.

Conclusions

TD still affects experienced Japanese tourists who visit Thailand. Although the proportions of the good levels of food and drink related behaviors were low, there were indications that Japanese tourists perceived the risk of contracting TD.

Oral cholera vaccines: use in clinical practice

Cholera continues to occur globally, particularly in sub-Saharan Africa and Asia. Oral cholera vaccines have been developed and have now been used for several years, primarily in traveller populations. The licensure in the European Union of a killed whole cell cholera vaccine combined with the recombinant B subunit of cholera toxin (rCTB-WC) has stimulated interest in protection against cholera. Because of the similarity between cholera toxin and the heat-labile toxin of Escherichia coli, a cause of travellers' diarrhoea, it has been proposed that the rCTB-WC vaccine may be used against travellers' diarrhoea. An analysis of trials of this vaccine against cholera (serotype O1) shows that for 4-6 months it will protect 61-86% of people living in cholera-endemic regions; lower levels of protection continue for 3 years. Protection wanes rapidly in young children. Because the risk of cholera for most travellers is extremely low, vaccination should be considered only for those working in relief or refugee settings or for those who will be travelling in cholera-epidemic areas and who will be unable to obtain prompt medical care. The vaccine can be expected to prevent 7% or less of cases of travellers' diarrhoea and should not be used for this purpose.

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.

Outbreak of enterotoxigenic Escherichia coli infection with an unusually long duration of illness

BACKGROUND

Enterotoxigenic Escherichia coli (ETEC) is an emerging cause of foodborne outbreaks of infection in the United States, yet its epidemiology is not completely understood.

METHODS

In September 2004, we investigated an outbreak of infection due to ETEC at an Illinois corporation following a meal served to approximately 700 employees. Clinical samples were negative for enteric pathogens and were tested for ETEC using stool culture and polymerase chain reaction (PCR). An environmental investigation was conducted to determine whether food-service practices or conditions led to this outbreak. A case of illness caused by ETEC was defined as onset of diarrhea and > or =1 of the following symptoms during 23-30 September 2004: cramps, vomiting, nausea, headache, or weight loss.

RESULTS

The 111 ill employees interviewed had only 1 meal in common. Cucumber salad and noodle salad from that meal were associated with illness; no food was available for testing. A PCR test for ETEC in stool was positive in samples from 6 of 11 patients; 3 ETEC serotypes were detected. The environmental investigation revealed no critical violations. The median duration of diarrhea (7 days) was longer than that observed for the majority of outbreaks of ETEC infection (4 days) and was associated with consumption of carbonated beverages (odds ratio, 4.5; 95% confidence interval, 2.0-10.3).

CONCLUSIONS

Emerging features of ETEC identified in this outbreak include the organism's role in domestic outbreaks and its ability to cause prolonged diarrheal illness. Additionally, integrating the results of nonculture-based diagnostic techniques into foodborne outbreak surveillance presents challenges under the current guidelines of the Centers for Disease Control and Prevention.

Importance of heat-labile enterotoxin in colonization of the adult mouse small intestine by human enterotoxigenic Escherichia coli strains

Enterotoxigenic Escherichia coli (ETEC) infections are a significant cause of diarrheal disease and infant mortality in developing countries. Studies of ETEC pathogenesis relevant to vaccine development have been greatly hampered by the lack of a suitable small-animal model of infection with human ETEC strains. Here, we demonstrate that adult immunocompetent outbred mice can be effectively colonized with the prototypical human ETEC H10407 strain (colonization factor antigen I; heat-labile and heat-stable enterotoxin positive) and that production of heat-labile holotoxin provides a significant advantage in colonization of the small intestine in this model.

Multiplex real-time PCR detection of heat-labile and heat-stable toxin genes in enterotoxigenic Escherichia coli

A multiplex real-time PCR method was developed for detection of heat-labile and heat-stable toxin genes in enterotoxigenic Escherichia coli. Approximately 10 CFU per reaction mixture could be detected in rinsates from produce samples. Several foods representative of varieties previously shown to have caused enterotoxigenic E. coli outbreaks were spiked and enriched for 4 or 6 h. Both heat-labile and heat-stable toxin genes could be detected in the foods tested, with the exception of hot sauce, with threshold cycle values ranging from 25.2 to 41.1. A procedure using membrane filtration which would allow enumeration of the enterotoxigenic E. coli population in a food sample in less than 28 h by real-time PCR analysis of colonies picked from media highly selective for E. coli was also developed.

Enterotoxigenic Escherichia coli in veterinary medicine

Enterotoxigenic Escherichia coli (ETEC) infection is the most common type of colibacillosis of young animals (primarily pigs and calves), and it is a significant cause of diarrhoea among travellers and children in the developing world. The main virulence attributes of ETEC are adhesins and enterotoxins, which are mostly regulated on large plasmids. Almost all ETEC bacteria are known to adhere to receptors on the small intestinal epithelium by their proteinaceous surface appendages (fimbriae, pili) or by afimbrial proteins without inducing significant morphological changes. Furthermore, they secrete protein toxins (enterotoxins) to reduce absorption and to increase fluid and electrolyte secretion of small intestinal epithelial cells. Regarding details of epidemiology, pathogenesis, diagnosis and prevention of ETEC infections and diarrhoea in animals, readers are referred to an earlier more extensive review [Nagy and Fekete, 1999. Enterotoxigenic Escherichia coli (ETEC) in farm animals. Vet. Res. 30, 259-284]. This paper intends to summarise our basic knowledge and to highlight the new developments and most actual research topics in the area of ETEC infections in veterinary medicine. Attention is paid to recently described new virulence factors and to new genetic vectors in ETEC bacteria. Applications of our knowledge in the diagnosis and prevention of ETEC diarrhoea in animals will also be discussed.

Traveller's diarrhoea

Traveller's diarrhoea affects over 50% of travellers to some destinations and can disrupt holidays and business trips. This review examines the main causes and epidemiology of the syndrome, which is associated with poor public health infrastructure and hygiene practices, particularly in warmer climates. Although travellers may be given common sense advice on avoidance of high-risk foods and other measures to prevent traveller's diarrhoea, adherence to such advice is sometimes difficult and the evidence for its effectiveness is contradictory. However, non-antimicrobial means for prevention of traveller's diarrhoea are favoured in most settings. A simple stepwise approach to the management of traveller's diarrhoea includes single doses or 3-day courses of antimicrobials, often self administered. The antibiotics of choice are currently fluoroquinolones or azithromycin, with an emerging role for rifaximin. In the long term, there will be greater benefit and effect on the health of local inhabitants and travellers from improving public health and hygiene standards at tourist destinations.

Emerging Causes of Traveler's Diarrhea: Cryptosporidium, Cyclospora, Isospora, and Microsporidia

Travel is a risk factor for acquiring infection with a spore-forming protozoa: Cryptosopridium, Cyclospora, Microsporidia, and Isospora. Certain travel destinations have a high disease burden and intense exposure. Patients present with persistent diarrhea and a history of recent travel to a developing country in the tropics. Very mild infections may be underdiagnosed and may cause typical traveler's diarrhea. In a patient with a history of travel and persistent diarrhea unresponsive to the usual antibiotic and antidiarrhea treatment, stool studies for all four of these protozoa infections should be performed. If immune status is normal and the disease is mild, symptomatic therapy may suffice. Effective treatment is available for Cyclospora, Microsporidia, and Isospora.