Travellers' diarrhoea: Impact of TD definition and control group design on study results

Safety and immunogenicity of ETVAX®, an oral inactivated vaccine against enterotoxigenic Escherichia coli diarrhoea: a double-blinded, randomized, placebo-controlled trial amongst Finnish travellers to Benin, West Africa

BACKGROUND

No licensed human vaccines are available against enterotoxigenic Escherichia coli (ETEC), a major diarrhoeal pathogen affecting children in low- and middle-income countries and foreign travellers alike. ETVAX®, a multivalent oral whole-cell vaccine containing four inactivated ETEC strains and the heat-labile enterotoxin B subunit (LTB), has proved promising in Phase 1 and Phase 1/ 2 studies.

METHODS

We conducted a Phase 2b double-blinded, randomized, placebo-controlled trial amongst Finnish travellers to Benin, West Africa. This report presents study design and safety and immunogenicity data. Volunteers aged 18-65 years were randomized 1:1 to receive ETVAX® or placebo. They visited Benin for 12 days, provided stool and blood samples and completed adverse event (AE) forms. IgA and IgG antibodies to LTB and O78 lipopolysaccharide (LPS) were measured by electrochemiluminescence.

RESULTS

The AEs did not differ significantly between vaccine (n = 374) and placebo (n = 375) recipients. Of the solicited AEs, loose stools/diarrhoea (26.7/25.9%) and stomach ache (23.0/20.0%) were reported most commonly. Of all possibly/probably vaccine-related AEs, the most frequent were gastrointestinal symptoms (54.0/48.8%) and nervous system disorders (20.3/25.1%). Serious AEs were recorded for 4.3/5.6%, all unlikely to be vaccine related. Amongst the ETVAX® recipients, LTB-specific IgA antibodies increased 22-fold. For the 370/372 vaccine/placebo recipients, the frequency of ≥2-fold increases against LTB was 81/2.4%, and against O78 LPS 69/2.7%. The majority of ETVAX® recipients (93%) responded to either LTB or O78.

CONCLUSIONS

This Phase 2b trial is the largest on ETVAX® undertaken amongst travellers to date. ETVAX® showed an excellent safety profile and proved strongly immunogenic, which encourages the further development of this vaccine.

Diarrhea and related personal characteristics among Japanese university students studying abroad in intermediate- and low-risk countries

Despite an increasing number of students studying abroad worldwide, evidence about health risks while they are abroad is limited. Diarrhea is considered the most common travelers' illness, which would also apply to students studying abroad. We examined diarrhea and related personal characteristics among Japanese students studying abroad. Japanese university students who participated in short-term study abroad programs between summer 2016 and spring 2018 were targeted (n = 825, 6-38 travel days). Based on a 2-week-risk of diarrhea (passing three or more loose or liquid stools per day) among travelers by country, the destination was separated into intermediate- and low-risk countries. After this stratification, the associations between personal characteristics and diarrhea during the first two weeks of their stay were evaluated using logistic regression models. Among participants in intermediate-risk countries, teenagers, males and those with overseas travel experience were associated with an elevated risk of diarrhea; the odds ratios (95% confidence intervals) were 2.42 (1.08-5.43) for teenagers (vs. twenties), 1.93 (1.08-3.45) for males (vs. females) and 2.37 (1.29-4.33) for those with overseas experience (vs. none). Even restricting an outcome to diarrhea during the first week did not change the results substantially. The same tendency was not observed for those in the low-risk countries. Teenage students, males and those with overseas travel experience should be cautious about diarrhea while studying abroad, specifically in intermediate-risk countries.

Characterization of Functional B-Cell Epitopes at the Amino Terminus of Shigella Invasion Plasmid Antigen B (IpaB)

Shigella invasion plasmid antigen B (IpaB) plays an important role in causing shigellosis. While IpaB's protein structure, contribution to disease mechanism, and protective immunity against Shigella infection have been well studied, the significance of individual antigenic domains, especially at the N terminus, has not been systematically characterized. In an attempt to identify IpaB protein functional epitopes and to construct an optimized polyvalent multiepitope fusion antigen (MEFA) immunogen for development of a protein-based cross protective Shigella vaccine, in this study, we in silico identified immunodominant B-cell epitopes from the IpaB N terminus, fused each epitope to carrier protein CsaB (the major subunit of enterotoxigenic Escherichia coli CS4 adhesin) for epitope fusion proteins, immunized mice with each epitope fusion protein, examined IpaB-specific antibody responses, and assessed antibody functional activity against Shigella bacterial invasion. A total of 10 B-cell continuous epitopes were identified from IpaB N terminus, and after being fused to carrier protein CsaB, each epitope induced anti-IpaB IgG responses in the intramuscularly immunized mice. While in vitro antibody invasion inhibition assays demonstrated that antibodies derived from each identified epitope were functional, epitopes 1 (LAKILASTELGDNTIQAA), 2 (HSTSNILIPELKAPKSL), and 4 (QARQQKNLEFSDKI) induced antibodies to inhibit Shigella sonnei and Shigella flexneri invasion at levels similar to those of recombinant IpaB protein, suggesting that these three IpaB epitopes can be used potentially as IpaB-representing antigens to induce protective anti-IpaB antibodies and for construction of an epitope-based polyvalent MEFA protein immunogen for Shigella vaccine development. IMPORTANCE Currently, there are no effective measures for control or prevention of Shigella infection, the most common cause of diarrhea in children 3 to 5 years of age in developing countries. Challenges in developing Shigella vaccines include virulence heterogeneity among species and serotypes. To overcome virulence heterogeneity challenge and to develop a protein-based multivalent Shigella vaccine, we targeted a panel of virulence factors, including invasion plasmid antigens, identified functional antigenic domains or epitopes as representative antigens, and applied the novel epitope- and structure-based vaccinology platform multiepitope fusion antigen (MEFA) to integrate functional antigenic domains or epitopes into a backbone immunogen to produce a polyvalent immunogen for cross protective antibodies. Identification of functional IpaB epitopes from this study enhances our understanding of IpaB immunogenicity and allows us to directly utilize IpaB epitopes for construction of a cross protective polyvalent Shigella immunogen and to accelerate development of a protein-based Shigella vaccine.

Doxycycline as an antimalarial: Impact on travellers' diarrhoea and doxycycline resistance among various stool bacteria - Prospective study and literature review

BACKGROUND

Antibiotics predispose travellers to acquire multidrug-resistant bacteria, such as extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-PE). Although widely used in antimalarial prophylaxis, doxycycline has scarcely been studied in this respect.

METHODS

We explored the impact of doxycycline on rates of traveller's diarrhoea (TD), ESBL-PE acquisition and, particularly, doxycycline co-resistance among travel-acquired ESBL-PE in a sample of 412 visitors to low- and middle-income countries. We reviewed the literature on traveller studies of doxycycline/tetracycline resistance among stool pathogens and the impact of doxycycline on TD rates, ESBL-PE acquisition, and doxycycline/tetracycline resistance.

RESULTS

The TD rates were similar for doxycycline users (32/46; 69.6%) and non-users (256/366; 69.9%). Of the 90 travel-acquired ESBL-PE isolates, 84.4% were co-resistant to doxycycline: 100% (11/11) among users and 82.3% (65/79) among non-users. The literature on doxycycline's effect on TD was not conclusive nor did it support a recent decline in doxycycline resistance. Although doxycycline did not increase ESBL-PE acquisition, doxycycline-resistance among stool pathogens proved more frequent for users than non-users.

CONCLUSIONS

Our prospective data and the literature review together suggest the following: 1) doxycycline does not prevent TD; 2) doxycycline use favours acquisition of doxy/tetracycline-co-resistant intestinal bacteria; 3) although doxycycline does not predispose to travel-related ESBL-PE acquisition per se, it selects ESBL-PE strains co-resistant to doxycycline; 4) doxycycline resistance rates are high among stool bacteria in general with no evidence of any tendency to decrease.

Bacterial travellers' diarrhoea: A narrative review of literature published over the past 10 years

Travellers' diarrhoea (TD) is the most frequent illness experienced by international travellers to lower-income countries with bacterial agents considered to account for 80-90% of cases. In this review, we summarise evidence published on bacterial TD over the past 10 years, focusing on the epidemiology and aetiology of TD. Diarrhoeagenic Escherichia coli (DEC) continue to be the most commonly implicated bacteria in TD, although Enteropathogenic E. coli (EPEC) and Enteroaggregative E. coli (EAEC) now appear to be predominant where Enterotoxigenic E. coli (ETEC) was previously considered most prevalent globally. Where fluroquinolone resistance had primarily been documented for Campylobacter in Southeast Asia, widespread resistance has been observed in most regions of the world for multiple enteropathogens, including Shigella, Salmonella, ETEC and EAEC. Implementation of novel molecular methods for pathogen detection has led to identification of bacterial pathogens, including Clostridium difficile (with and without the use of prior antibiotics), Arcobacter species and Bacteroides fragilis, as aetiological agents in TD. The widespread resistance to first-line antibiotics in multiple bacterial enteropathogens warrants continued surveillance and re-evaluation of current treatment practices. Further investigations are required to determine the prevalence and geographical distribution of bacterial enteropathogens that have been more recently implicated in TD.

Bacterial, viral and parasitic pathogens analysed by qPCR: Findings from a prospective study of travellers' diarrhoea

BACKGROUND

The diagnostics of travellers' diarrhoea (TD) has been revolutionised by multiplex qPCR assays. While mostly of bacterial aetiology, viruses and parasites account for the disease among 10-20% of travellers. Despite this, prospective studies applying qPCR assays remain scarce that cover not only bacteria, such as the various diarrhoeagenic Escherichia coli (DEC), but also viral and parasitic pathogens.

METHOD

We analysed by qPCR pre- and post-travel stool samples of 146 Finnish travellers for bacterial, viral and parasitic pathogens: enteropathogenic (EPEC), enteroaggregative (EAEC), enterotoxigenic (ETEC), enterohaemorrhagic (EHEC), and enteroinvasive (EIEC) E. coli; Shigella, Campylobacter, Salmonella, Yersinia and Vibrio cholerae; norovirus G1 and G2, rotavirus, enteroviruses, and sapovirus; and Giardia lamblia, Entamoeba histolytica, and Cryptosporidium. Symptoms and medication data during travel were collected by questionnaires.

RESULTS

We detected bacterial pathogens in 102/146 samples (69.9%; EAEC, EPEC, ETEC most common), viral ones in 13 (8.9%; norovirus most common), and parasitic ones in one (0.7%; Giardia). Noroviruses were associated with severe symptoms (23.5% versus non-severe 4.9%). In the TD group, 41.7% (5/12) of those with viral pathogens (vs. 13.3%; 11/83 without) took antibiotics.

CONCLUSION

Viral pathogens, particularly noroviruses, prevail in severe TD. The symptoms of viral disease are often severe and lead to unwarranted use of antibiotics.

Surveillance of enteropathogenic bacteria, protozoa and helminths in travellers returning from the tropics

Diarrhoea is a frequent symptom associated with travelling to tropical regions, but the cause is often not found. Epidemiology was assessed including up-to-date real-time PCR approaches.We analysed datasets of 528 patients who presented at the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany, between 2006 and 2010 for screening purposes or because of diarrhoea. Stool samples were obtained and investigated by microscopy, bacterial culture, two PCR assays targeting Entamoeba histolytica, Entamoeba dispar, Giardia duodenalis, and Cryptosporidium parvum, or Salmonella spp., Shigella/EIEC spp., Campylobacter jejuni, and Yersinia spp.Among patients with gastrointestinal symptoms, 51% tested positive for bacteria or parasites, of which 66% had a known enteropathogenic potential. In patients without diarrhoea, 53% (n = 80) were positive, and 33% of these cases harboured agents of pathogenic potential. Association with clinical symptoms was primarily found for bacterial infections. Blastocystis hominis, however, was more frequent in asymptomatic than in symptomatic travellers.In conclusion, the study stresses the etiological relevance of bacterial gastroenteritis in travellers returning from the tropics, the need for molecular approaches to increase diagnostic sensitivity and demonstrates that asymptomatic carriage of enteropathogens after prolonged stays in the tropics is similarly frequent compared with symptomatic infections in travellers.

Acquisition of multidrug-resistant Enterobacterales during international travel: a systematic review of clinical and microbiological characteristics and meta-analyses of risk factors

BACKGROUND

International tourism increased from 25 million tourist arrivals in 1950 to over 1.3 billion in 2017. These travelers can be exposed to (multi) resistant microorganisms, may become colonized, and bring them back home. This systematic review aims to identify the carriage rates of multidrug-resistant Enterobacterales (MDR-E) among returning travelers, to identify microbiological methods used, and to identify the leading risk factors for acquiring MDR-E during international travel.

METHODS

Articles related to our research question were identified through a literature search in multiple databases (until June 18, 2019) - Embase, Medline Ovid, Cochrane, Scopus, Cinahl, Web of Science, and Google Scholar.

RESULTS

Out of 3211 potentially relevant articles, we included 22 studies in the systematic review, and 12 studies in 7 random-effects meta-analyses. Highest carriage rates of MDR-E were observed after travel to Southern Asia (median 71%), followed by travel to Northern Africa (median 42%). Carbapenemase-producing Enterobacterales (CPE) were identified in 5 out of 22 studies, from a few patients. However, in only eight out of 22 studies (36.4%) the initial laboratory method targeted detection of the presence of CPE in the original samples. The risk factor with the highest pooled odds ratio (OR) for MDR-E was travel to Southern Asia (pooled OR = 14.16, 95% confidence interval [CI] = 5.50 to 36.45), followed by antibiotic use during travel (pooled OR = 2.78, 95% CI = 1.76 to 4.39).

CONCLUSIONS

Risk of acquiring MDR-E while travelling increases depending on travel destination and if antibiotics are used during travel. This information is useful for the development of guidelines for healthcare facilities with low MDR-E prevalence rates to prevent admission of carriers without appropriate measures. The impact of such guidelines should be assessed.

Traveler's diarrhea in children: New insights and existing gaps

The number of children accompanying their parents in international travel is increasing steadily, and with the rising global migration, children more frequently accompany their parents or caregivers for visiting friends or relatives (VFR). As compared to travel for tourism, VFR children are at higher risk of acquiring local diseases, as they more often stay in rural areas in resource-poor locations, have longer periods of visit, are less likely to attend pre-travel consultations, and less frequently adhere to recommended precautions. Travelers's diarrhea (TD) is the most common travel-associated illnesses in children. This review updates the existing knowledge on TD in children, regarding its distinctive epidemiology, risk factors, preventive measures, clinical manifestations, complications, causative microorganisms and management. Despite the limited focused research on pediatric TD, which challenges the formulation of children-oriented evidence-based guidelines, practical recommendations are suggested.

Impact of alcohol-based hand-gel sanitizer and hand hygiene advice on travellers' diarrhoea and colonization with extended-spectrum beta-lactamase-producing Enterobacteriaceae: A randomised, controlled trial

BACKGROUND

Travellers' diarrhoea (TD) is the most common health problem in international travellers. Besides being bothersome for the individual and a considerable economic burden for the public, TD is also known to be associated with becoming colonized with extended-spectrum β-lactamase (ESBL)-producing Enterobacteriacea. Despite the high frequency of TD cases, easy and effective preventive measures are lacking. The aim of this study was to assess the impact of using hand gel sanitizer on the incidence of TD and colonization with ESBL-producing Enterobacteriaceae.

METHOD

A multicentre randomized intervention trial studying the effect of hand gel sanitizer on the incidence of TD and colonization with ESBL-producing Enterobacteriaceae in travellers to Southeast Asia was performed.

RESULTS

The intention to treat analysis showed a reduction in the incidence of WHO TD in the intervention group (OR 0.54 (95% CI 0.30-0.97), p = 0.04). No effect was seen or the incidence of becoming colonized with ESBL-producing Enterobacteriaceae.

CONCLUSION

Using hand gel sanitizer might have a protective effect on the occurrence of TD. Based on the current data, education on the proper use appears to play a key role for its effectiveness.

Despite antibiotic treatment of travellers' diarrhoea, pathogens are found in stools from half of travellers at return

BACKGROUND

Among visitors to the (sub)tropics, 20-50% contract travellers' diarrhoea (TD) and 5-30% take antibiotics. While shortening the duration of illness, antimicrobials predispose to acquisition of multi-drug resistant bacteria. Therefore, liberal use is no longer advocated. Although antibiotics kill pathogens, no data support the view that they could prevent post-infectious sequelae. We investigated how antibiotic use for TD abroad impacts the pathogen findings at return.

MATERIALS AND METHODS

We revisited 456 travellers' clinical data and stool pathogens examined by qPCR for Salmonella, Yersinia, Campylobacter, Shigella, Vibrio cholerae and enteroaggregative (EAEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), enterohaemorrhagic (EHEC) and enteroinvasive (EIEC) Escherichia coli.

RESULTS

Among travellers with TD, antibiotic users had pathogen-positive samples less frequently than non-users (50% versus 83%). The difference was significant for EPEC (23% versus 47%) and EAEC (27% versus 54%), but not ETEC (17% versus 26%) or the other pathogens. Shigella/EIEC was found more often among antibiotic users than non-users (4% versus 1%).

CONCLUSION

Despite antibiotic treatment of TD, half of the users still had stool pathogens at return, reflecting either antibiotic resistance of pathogens or recolonisation/reinfection while abroad. Treatment of TD with antibiotics during travel should not be interpreted to indicate eradication of pathogens.