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

Evidence of pathogens associated with travelers' diarrhea in Thailand: a systematic review

BACKGROUND

Thailand, a major tourist destination, exhibits variations in sanitation and food safety practices that can lead to cases of travelers' diarrhea (TD) caused by a plethora of pathogens. This systematic review synthesizes data on the pathogens associated with TD in Thailand, providing valuable insights into pathogen diversity and distribution, traveler profiles, and geographical regions of concern.

METHODS

This systematic review followed the PRISMA guidelines and was registered in PROSPERO (CRD42022346014). A comprehensive search was conducted across PubMed, Embase, Scopus, MEDLINE, and Journals@Ovid databases. The search included terms related to "diarrhea," "travelers," and "Thailand," without restrictions on publication date. Eligible studies focused on travelers to Thailand who developed diarrhea with identified specific pathogens. Data was extracted and synthesized using a narrative approach. The risk of bias was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist.

RESULTS

A total of 15 studies met the eligibility criteria, identifying that pathogens related to TD in Thailand were bacteria, particularly enterotoxigenic Escherichia coli (ETEC) (80%), followed by Campylobacter jejuni (33.3%) and Salmonella spp. (40%). Viral pathogens such as rotavirus and norovirus were also notable, with Giardia spp. being the most identified parasite. Pathogen distribution varied across different regions of Thailand, with tourism hubs such as Bangkok, Chiang Mai, Phuket, and Krabi reporting a broader range of infections.

CONCLUSIONS

This systematic review highlights the diverse range of pathogens associated with TD in Thailand, with bacterial pathogens, specifically ETEC, being the predominant cause in most studies. The findings underscore the importance of preventive measures, such as improved hygiene practices and food safety awareness, especially in high-risk tourist areas. Further research is needed to understand better the risk factors contributing to TD and to develop targeted interventions for prevention.

Angelicae Pubescentis Radix Remitted Intestine Damage in Mice Induced by Escherichia coli via Mediating Antioxidant Defense, Inflammatory Mediators, and Restoring Gut Microbiota

This study aims to explore the therapeutic potential of Angelicae Pubescentis Radix (APR), a traditional Chinese medicine that is widely known for its anti-inflammatory, anti-oxidative, and anti-microbial properties, using a mouse model. In this study, 30 mice were selected and divided into three groups: control group (CD), infection group (ED), and treatment group (TD). Mice in the TD were gavaged with APR oil (0.15 mL/kg/day) for 20 days, while mice in the CD and ED received an equal volume of normal saline. On the 21st day, mice in the ED and TD were infected with multi-drug-resistant E. coli (1 × 107 CFU/mL) derived from diarrheal yak. Twenty-four hours later, all mice were euthanized, and blood, organs, and intestinal samples were collected for analysis. The results of intestinal sections and intestinal bacterial load revealed that APR treatment significantly reduced (p < 0.05) both bacterial load and intestinal injury. Serum analysis indicated that APR treatment also alleviated the inflammation and oxidative stress induced by E. coli infection. Intestinal microbiota sequencing further showed that APR treatment increased the abundance of intestinal probiotics such as Ligilactobacillus, Paludicola, and Blautia_A_1417806 while also enhancing the enrichment of functional pathways associated with antioxidant defense. In conclusion, APR treatment effectively alleviates diseases caused by E. coli infection, promotes the growth of beneficial intestinal bacteria, and improves the antioxidant capacity in animals. Additionally, these findings confirm APR's role in addressing immediate effects rather than chronic adaptations. Future studies should investigate the prolonged effects of APR treatment beyond the acute phase.

Reporting of Salmonellosis Markedly Declined in Finland During 28 Years of Surveillance, 1995-2022

Salmonellosis is the second most common foodborne bacterial gastroenteritis in humans in Finland and worldwide. In Finland, a national salmonella control program covering cattle, pigs, and poultry, as well as the meat and eggs obtained from them, has been in place since the country joined the EU in 1995. To identify trends in the incidence of salmonellosis and to reflect on their causes, we analyzed Salmonella case data from the Finnish Infectious Disease Register (FIDR) from 1995 to 2022 and outbreak data from the national food and waterborne outbreak register (the FWO register) in the period 2010-2022. From 1995-1999 to 2015-2019, the incidence of salmonellosis decreased by 66% and 63% for domestic and travel-related cases, respectively. Most salmonellosis cases (72%) were travel-related, and, of them, 27% were infected in Southeast Asia. The most common serovars were S. Typhimurium and S. Enteritidis (38% and 19% of domestic cases, and 7% and 39% of travel-related cases). During 2010-2022, Salmonella sp. was reported as a cause in 31 foodborne outbreaks. In 14 of them, the source was identified at foodstuff level, and 12 sources were of foreign origin. The results of this study indicate that the national salmonella control program may have prevented domestic human infections in Finland.

Putting the mouth back in the body - the neglected area of dental and oral travel health

The lack of dental travel health care has been deplored for some time. Travel medicine's remit is to prepare people for travel. People travel with their mouth firmly in their body, yet the mouth's wellbeing does not rate a mention. This article represents the first exploration of a range of topics relevant to an until now neglected, yet potentially highly important, area of health care. A range of dental mishaps can occur while away from home, from simple toothache to accidents, serious emergencies, or restoration failures. Other problems originate in unwise behaviour, including holiday-inspired body modifications.Unless there is pain, teeth are typically not thought about much. However, examining the practical side of dental hygiene during travels, several overlooked and perhaps surprising topics emerge that - through the travel lens - take on a different and important role: the oral microbiome, toothbrush hygiene, the toilet plume, and traveller diarrhoea. Based on this discussion, recommendations are made for clinical practice, education, and further research.The historical chasm between dentistry and medicine, despite long-standing calls for change, does not seem to go away and impairs holistic high quality travel health care. Travel medicine can bypass this unproductive division. It has the unique opportunity to be the first medical specialty cooperating closely with dentists to bridge this gap by providing quality travel health care to travellers with all their body parts attached.

Wastewater-borne viruses and bacteria, surveillance and biosensors at the interface of academia and field deployment

Wastewater is a complex, but an ideal, matrix for disease monitoring and surveillance as it represents the entire load of enteric pathogens from a local catchment area. It captures both clinical and community disease burdens. Global interest in wastewater surveillance has been growing rapidly for infectious diseases monitoring and for providing an early warning of potential outbreaks. Although molecular detection methods show high sensitivity and specificity in pathogen monitoring from wastewater, they are strongly limited by challenges, including expensive laboratory settings and prolonged sample processing and analysis. Alternatively, biosensors exhibit a wide range of practical utility in real-time monitoring of biological and chemical markers. However, field deployment of biosensors is primarily challenged by prolonged sample processing and pathogen concentration steps due to complex wastewater matrices. This review summarizes the role of wastewater surveillance and provides an overview of infectious viral and bacterial pathogens with cutting-edge technologies for their detection. It emphasizes the practical utility of biosensors in pathogen monitoring and the major bottlenecks for wastewater surveillance of pathogens, and overcoming approaches to field deployment of biosensors for real-time pathogen detection. Furthermore, the promising potential of novel machine learning algorithms to resolve uncertainties in wastewater data is discussed.

Landscape of Bacterial Enteric Disease and Traveler´s Diarrhea in South America

Diarrheal disease is a global public health threat. Cases of enteric disease caused by bacterial enteropathogens result in a significant health burden and can lead to antimicrobial resistance patterns that increase and evolve over time and geography, posing serious health challenges for local populations as well as civilian travelers and military personnel deployed to endemic regions. This review describes the prevalence of the most common bacterial agents of diarrheal disease in South America, as well as the distribution patterns of antibiotic resistance and predominant strains that are present in the region. Furthermore, the development of relevant prevention and treatment strategies are described, and United States Naval Medical Research Unit SOUTH disease surveillance and enteric disease research efforts in this regional context are highlighted.

Treatment of lactoferrin and antimicrobial peptide N6 on bacterial enteritis caused by Escherichia coli in mice

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in humans and animals. The study aimed to evaluate the efficacy of bovine lactoferrin (bLf) as an adjuvant combined with AMP (N6) in the treatment of E. coli-induced bacterial enteritis. Firstly, 40 female ICR mice were randomly divided into four groups. The ETEC-A, ETEC-B, and ETEC-C groups were gavaged with 0.2 mL of ETEC K88 at 5 × 109, 5 × 108, and 5 × 107 CFU/mL for three consecutive days, respectively, the CK control group was given PBS. Based on the clinical symptoms and intestinal changes, the optimal model dose of ETEC K88 was determined to be 5 × 108 CFU/mL. Sixty female ICR mice were randomly divided into six groups: CK group (uninfected), NC group (infected and untreated), N6 treatment group (20 mg/kg), bLf treatment group (100 mg/kg), bLf + N6-A treatment group (10 mg/kg N6+100 mg/kg bLf), and bLf + N6-B group (20 mg/kg N6+100 mg/kg bLf). The clinical symptoms, intestinal morphology, inflammatory response and serum metabolites were monitored. The results showed that compared with the NC group, the bLf-N6-A and bLf-N6-B treatment groups had significant reductions in TNF-α and IL-6, significant increases in IL-10, and significant reductions in endotoxin and DAO in plasma (p < 0.05). Meanwhile, the bLf-N6-A and bLf-N6-B treatment groups significantly increased the expression of ZO-1, claudin-1 and occludin, increased the height of small intestinal mucosal villi and VH/CD after ETEC K88-induced intestinal injury (p < 0.05). The combination of bLf and N6 relieved enteritis by balancing intestinal mucosal immunity, improving intestinal morphology and barrier function. BLf combined with N6 can be used as an effective therapeutic strategy for the treatment of bacterial enteritis.

Recent Antimicrobial Resistance Situation and Mechanisms of Resistance to Key Antimicrobials in Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in developing countries and is regularly imported into developed countries as a major cause of traveler's diarrhea. ETEC is usually self-limiting and not necessarily treated with antimicrobials, although antimicrobial treatment is recommended in malnourished children, severe cases, and traveler's diarrhea. However, resistant strains to representative therapeutic agents such as ciprofloxacin and azithromycin have been reported in recent years, and multidrug-resistant ETEC has also emerged. This review discusses the recent antimicrobial resistance surveillance in ETEC and the mechanisms of resistance to major antimicrobials.

What Do Travelers Know about Traveler's Diarrhea? Impact of a Pre-Travel Consultation in the Lisbon Area, Portugal

Traveler's diarrhea (TD) is one of the most common travel-related health problems, largely interfering with planned activities and potentially contributing to antimicrobial resistance. This study aimed to characterize the knowledge about TD among pre-travel consultation users of one Portuguese travel clinic and determine the impact of the consultation on knowledge levels. Using a quasi-experimental, separate-sample pretest-posttest design, participants were randomly assigned to two groups: control/pre-consultation group (CG) or experimental/post-consultation group (EG). An anonymous self-administered questionnaire was used. A total of 470 participants were analyzed (227 CG; 243 EG). The EG/post-consultation group showed significant improvement in knowledge, with correct answers increasing from 63% to 75% (p < 0.001). However, knowledge gaps persisted: over 50% were unaware of TD's self-limited nature, 30% did not recognize loperamide as a symptom reliever, and 36% believed all travelers should take antibiotics to prevent TD. The educational level and previous travel outside Europe influenced baseline knowledge; previous travel medicine consultations and information on TD improved knowledge in both groups and made it easier to acquire knowledge on the subject. Thus, a pre-travel consultation effectively increased travelers' TD knowledge. However, post-consultation knowledge levels remained suboptimal, indicating the need for targeted interventions to increase travelers' literacy and optimize pre-travel consultations.

Enteroaggregative Escherichia coli in mid-Norway: A prospective, case control study

BACKGROUND

The use of molecular methods has led to increased detection of Enteroaggregative Escherichia coli (EAEC) in faecal samples. Studies have yielded conflicting results regarding the clinical relevance of this finding. The objective of this study was to investigate the prevalence of EAEC in faecal samples from patients with diarrhoea and healthy controls and describe characteristics of EAEC positive persons.

METHODS

From March 1st, 2017 to February 28th, 2019, we investigated all consecutive faecal samples from patients with diarrhoea received at the laboratory and collected faecal samples from randomly invited healthy controls from mid-Norway. Real-time multiplex PCR was used for detection of bacterial, viral, and parasitic pathogens. We registered sex, age, urban versus non-urban residency, and travel history for all participants. Statistical analyses were performed with Pearson chi-squared test, Kruskal-Wallis test, and Mann-Whitney U test.

RESULTS

We identified EAEC in 440 of 9487 (4.6%) patients with diarrhoea and 8 of 375 (2.2%) healthy controls. The EAEC prevalence was 19.1% among those with diarrhoea and recent foreign travel and 2.2% in those without travel history independent of diarrhoea. Concomitant pathogens were detected in 64.3% of EAEC-positive patients with diarrhoea. The median age was 28.5 in those with EAEC-positive diarrhoea and 38 in those with EAEC-negative diarrhoea (p <0.01). In patients with diarrhoea, travel was reported in 72% of those with EAEC and concomitant pathogens, and 54% and 12% in those with only EAEC and no EAEC, respectively (p <0.01).

CONCLUSIONS

EAEC was a common detection, particularly in patients with diarrhoea and recent international travel, and was found together with other intestinal pathogens in the majority of cases. Our results suggest that domestically acquired EAEC is not associated with diarrhoea. Patients with EAEC-positive diarrhoea and concomitant pathogens were young and often reported recent travel history compared to other patients with diarrhoea.

Subjects' Sociodemographics Influence the Transmission Patterns of Diarrheagenic Escherichia coli Pathotypes among Children under 5 Years in Nakuru County

BACKGROUND

Diarrheagenic Escherichiacoli (DEC) infections constitute the leading causes of morbidity and mortality among children in Sub-Saharan Africa. However, little has so far been done to properly reveal the pathogenic endowments of DEC in these populations.

AIMS AND OBJECTIVES

We evaluated 4 DEC strains among children under 5 years.

MATERIALS AND METHODS

A cross-sectional study design was employed among 384 positive cases.

RESULTS

There was a significant decline in infections associated with DEC as the children grew older (χ2[12] = 87.366: P = [0.000]. A total of 56 (14.6%) cases were 0-12 months, 168 (43.8%) were 13-24 months, 88 (22.9%) were 25-36 months, 40 (10.4%) were 37-48 months, and 32 (8.3%) were 49-60 months. A total of 248 (64.6%) male subjects exhibited more susceptibility to DEC infections than their female counterparts (n = 136 [35.4%]) (χ2[3] =13.313: P = [0.004]. Subjects from urban areas (n = 248 [64.6%]), significantly bored the brunt of infections than those from rural areas (n = 136 [35.4%]) (χ2[3] = 35.147: P = [0.000]. The prevalence of DEC appeared significantly higher during rainy seasons (n = 269 [70.1%]).

CONCLUSION

Young age, male gender, crowding, and rainy season play a central role in the transmission of DEC pathotypes.

Prevalence and Antimicrobial Resistance of Campylobacter Species and Associated Factors Among Under-Five Children with Diarrhea at Randomly Selected Public Health Facilities in Mekelle, Tigray, Ethiopia

Background

Campylobacter species are the most predominant bacterial agents to cause diarrhea in under-five children. It poses a serious challenge to public health worldwide with ongoing acquisition of resistance to different antimicrobials with multiple patterns. Thus, this study aimed to determine the prevalence, and antimicrobial resistance of Campylobacter species, and associated factors among under-five children with diarrhea in selected public health facilities.

Methods

A cross-sectional study was conducted among under-five children with diarrhea using convenient sampling. Health facilities were selected using a simple random sampling method. The stool samples collected from 214 study participants were transported and processed following standard microbiological protocols. Campylobacter isolates were identified using Gram staining, biochemical test, serological test, and aerobic growth at 25°C. Antimicrobial susceptibility profiles of isolates were performed using the Kirby-Bauer method. Data were analyzed using SPSS ver. 25.0. Association between variables was assessed using Chi-square test and Logistic regression, with P ≤ 0.05.

Results

The subject's mean age was 31.3 (±3.9) months. Of the 214 samples cultured, 14 (6.5%) of them were positive for Campylobacter species with 95% CI (3.3-10.3). Out of the isolated species, 12 (85.7%) were Campylobacter jejuni /Campylobacter coli and 2 (14.3%) were other Campylobacter species. Bottle feeding and history of direct contact to domestic animals were associated with Campylobacter species (AOR=5.13, CI=1.21-21.6, p=0.026 and AOR=4.93, CI=1.33-18.17, P=0.016), respectively. Campylobacter isolates were highly resistant to ciprofloxacin 5 (35.7%), and tetracycline 3 (21.4%).

Conclusion

A higher incidence of Campylobacter species was obtained in children who were bottle-fed and who had a history of direct contact with domestic animals. The isolates were highly resistant to ciprofloxacin and tetracycline. These findings indicate that special attention is needed for better management of Campylobacter drug resistance in under-five children. To enhance and support our current findings, further research using molecular techniques is needed to identify the resistant and virulent genes of the bacterial isolates.

Etiology and Epidemiology of Travelers' Diarrhea among US Military and Adult Travelers, 2018-2023

Travelers' diarrhea has a high incidence rate among deployed US military personnel and can hinder operational readiness. The Global Travelers' Diarrhea study is a US Department of Defense--funded multisite surveillance effort to investigate the etiology and epidemiology of travelers' diarrhea. During 2018-2023, we enrolled 512 participants at partner institutions in 6 countries: Djibouti, Georgia, Egypt, Honduras, Nepal, and Peru. Harmonized laboratory methods conducted at each partner institution identified >1 pathogens, including Escherichia coli (67%-82%), norovirus (4%-29%), and Campylobacter jejuni (2%-20%), in 403 (79%) cases. Among cases, 79.7% were single infections, 19.6% were double infections, and 0.7% were triple infections. The most common enterotoxigenic E. coli colonization factors identified were CS3 (25%) and CS21 (25%), followed by CS2 (18%) and CS6 (15%). These data can inform best treatment practices for travelers' diarrhea and support US military health readiness.

Epidemiological trends of traveler's diarrhea in Japan: An analysis of imported infectious disease registry data from 2017-2022

Traveler's diarrhea (TD) is a global problem, and identifying the causative organisms of TD is important for adequate treatment. Therefore, this study retrospectively analyzed TD cases in patients who returned to Japan after traveling abroad to determine the causative organisms by travel region. We included patients with a final diagnosis of TD registered in the Japan Registry for Infectious Diseases from Abroad database from September 25, 2017, to September 1, 2022, from 14 medical institutions. A total of 919 patients were analyzed; the causative TD pathogen was identified in 188 cases (20%), of which 154 were caused by diarrheagenic bacteria, the most common being Campylobacter spp. (64%). A 2.2 mg/dL C-reactive protein concentration cutoff value had some predictive ability for bacterial TD (negative predictive value, 89%). Therefore, the C-reactive protein level may help rule out bacterial diarrhea and prevent unnecessary antimicrobial administration when patients cannot provide a stool specimen.

Colonizing foreign terrain: Insights into bacterial enteropathogens

In this present issue of the Biomedical Journal insights into pediatric campylobacteriosis are granted, and a potential path to developing a parenteral vaccine against enterotoxigenic E. coli is demonstrated. Additionally, a study shows how the use of extracorporeal shockwave therapy contributes to countering osteonecrosis of the femoral head. Furthermore, the relation between intimate partner violence and a saliva biomarker is explored. Finally, findings concerning the risk of dementia in patients with autonomic nervous system dysregulation are elucidated; and patterns of non-Alzheimer disease pathophysiology in individuals with depressive disorder are revealed.

Development of a new travellers' diarrhoea clinical severity classification and its utility in confirming rifamycin-SV efficacy

BACKGROUND

travellers' diarrhoea (TD) is frequently reported with incidence up to 40% in high-risk destinations. Previous studies showed that the number of loose stools alone is inadequate to holistically predict the severity of TD. To improve the prediction of prognosis and to optimize treatments, a simple risk-based clinical severity classification has been developed.

METHODS

pooled baseline data of signs and symptoms and number of loose stools from 1098 subjects enrolled in two double-blind Phase 3 trials of rifamycin-SV were analyzed with correlation, multiple correspondence analyses, prognostic factor criteria, and Contal and O'Quigley method to generate a TD severity classification (mild, moderate and severe). The relative importance of this classification on resolution of TD was assessed by Cox proportional model hazard model on the time to last unformed stool (TLUS).

RESULTS

the analysis showed that TLUS were longer for the severe [hazard ratio (HR) 0.24; P < 0.001; n = 173] and moderate (HR 0.54; P = 0.0272; n = 912) vs mild. Additionally, when the treatment assigned in the studies was investigated in the severity classification, the results yielded that rifamycin-SV significantly shortened TLUS vs placebo for all subjects (HR 1.9; P = 0.0006), severe (HR 5.9; P = 0.0232) and moderate (HR 1.7; P = 0.0078) groups and was as equally efficacious as ciprofloxacin for all subjects, moderate and severe groups (HRs: 0.962, 0.9, 1.2; all P = NS, respectively). When reassessed by this classification, rifamycin-SV showed consistent efficacy with the Phase 3 studies.

CONCLUSIONS

this newly developed TD clinical severity classification demonstrated strong prognostic value and clinical utility by combining patients' multiple signs and symptoms of enteric infection and number of loose stools to provide a holistic assessment of TD. By expanding on the current classification by incorporating patient reported outcomes in addition to TLUS, a classification like the one developed, may help optimize patient selection for future clinical studies.

The role of the minor colonization factor CS14 in adherence to intestinal cell models by geographically diverse ETEC isolates

Enterotoxigenic Escherichia coli (ETEC) is a primary causative agent of diarrhea in travelers and young children in low- to middle-income countries. ETEC adheres to small intestinal epithelia via colonization factors (CFs) and secretes heat-stable toxin and/or heat-labile toxin, causing dysregulated ion transport and water secretion. There are over 30 CFs identified, including major CFs associated with moderate-to-severe diarrhea (MSD) and minor CFs for which a role in pathogenesis is less clear. The Global Enteric Multicenter Study identified CS14, a class 5a fimbriae, as the only minor CF significantly associated with MSD and was recommended for inclusion in ETEC vaccines. Despite detection of CS14 in ETEC isolates, the sequence conservation of the CS14 operon, its role in adherence, and functional cross-reactivity to other class 5a fimbriae like CFA/I and CS4 are not understood. Sequence analysis determined that the CS14 operon is >99.9% identical among seven geographically diverse isolates with expanded sequence analysis demonstrating SNPs exclusively in the gene encoding the tip adhesin CsuD. Western blots and electron microscopy demonstrated that CS14 expression required the growth of isolates on CFA agar with the iron chelator deferoxamine mesylate. CS14 expression resulted in significantly increased adherence to cultured intestinal cells and human enteroids. Anti-CS14 antibodies and anti-CS4 antibodies, but not anti-CFA/I antibodies, inhibited the adherence of a subset of ETEC isolates, demonstrating CS14-specific inhibition with partial cross-reactivity within the class 5a fimbrial family. These data provide support for CS14 as an important fimbrial CF and its consideration as a vaccine antigen in future strategies. IMPORTANCE Enterotoxigenic Escherichia coli (ETEC) infection causes profuse watery diarrhea in adults and children in low- to middle-income countries and is a leading cause of traveler's diarrhea. Despite increased use of rehydration therapies, young children especially can suffer long-term effects including gastrointestinal dysfunction as well as stunting and malnutrition. As there is no licensed vaccine for ETEC, there remains a need to identify and understand specific antigens for inclusion in vaccine strategies. This study investigated one adhesin named CS14. This adhesin is expressed on the bacterial surface of ETEC isolates and was recently recognized for its significant association with diarrheal disease. We demonstrated that CS14 plays a role in bacterial adhesion to human target cells, a critical first step in the disease process, and that adherence could be blocked by CS14-specific antibodies. This work will significantly impact the ETEC field by supporting inclusion of CS14 as an antigen for ETEC vaccines.

Comparison of the Diagnostic Accuracy of Three Real-Time PCR Assays for the Detection of Arcobacter butzleri in Human Stool Samples Targeting Different Genes in a Test Comparison without a Reference Standard

Potential etiological relevance for gastroenteric disorders including diarrhea has been assigned to Arcobacter butzleri. However, standard routine diagnostic algorithms for stool samples of patients with diarrhea are rarely adapted to the detection of this pathogen and so, A. butzleri is likely to go undetected unless it is specifically addressed, e.g., by applying pathogen-specific molecular diagnostic approaches. In the study presented here, we compared three real-time PCR assays targeting the genes hsp60, rpoB/C (both hybridization probe assays) and gyrA (fluorescence resonance energy transfer assay) of A. butzleri in a test comparison without a reference standard using a stool sample collection with a high pretest probability from the Ghanaian endemicity setting. Latent class analysis was applied with the PCR results obtained with a collection of 1495 stool samples showing no signs of PCR inhibition to assess the real-time PCR assays' diagnostic accuracy. Calculated sensitivity and specificity were 93.0% and 96.9% for the hsp60-PCR, 100% and 98.2% for the rpoB/C-PCR, as well as 12.7% and 99.8% for the gyrA-PCR, respectively. The calculated A. butzleri prevalence within the assessed Ghanaian population was 14.7%. As indicated by test results obtained with high-titer spiked samples, cross-reactions of the hsp60-assay and rpoB/C-assay with phylogenetically related species such as A. cryaerophilus can occur but are less likely with phylogenetically more distant species like, e.g., A. lanthieri. In conclusion, the rpoB/C-assay showed the most promising performance characteristics as the only assay with sensitivity >95%, albeit associated with a broad 95%-confidence interval. In addition, this assay showed still-acceptable specificity of >98% in spite of the known cross-reactivity with phylogenetically closely related species such as A. cryaerophilus. If higher certainty is desired, the gyrA-assay with specificity close to 100% can be applied for confirmation testing with samples showing positive rpoB/C-PCR results. However, in case of a negative result in the gyrA-assay, this cannot reliably exclude the detection of A. butzleri in the rpoB/C-assay due to the gyrA-assay's very low sensitivity.

Highly-conserved regulatory activity of the ANR family in the virulence of diarrheagenic bacteria through interaction with master and global regulators

ANR (AraC negative regulators) are a novel class of small regulatory proteins commonly found in enteric pathogens. Aar (AggR-activated regulator), the best-characterized member of the ANR family, regulates the master transcriptional regulator of virulence AggR and the global regulator HNS in enteroaggregative Escherichia coli (EAEC) by protein-protein interactions. On the other hand, Rnr (RegA-negative regulator) is an ANR homolog identified in attaching and effacing (AE) pathogens, including Citrobacter rodentium and enteropathogenic Escherichia coli (EPEC), sharing only 25% identity with Aar. We previously found that C. rodentium lacking Rnr exhibits prolonged shedding and increased gut colonization in mice compared to the parental strain. To gain mechanistic insights into this phenomenon, we characterized the regulatory role of Rnr in the virulence of prototype EPEC strain E2348/69 by genetic, biochemical, and human organoid-based approaches. Accordingly, RNA-seq analysis revealed more than 500 genes differentially regulated by Rnr, including the type-3 secretion system (T3SS). The abundance of EspA and EspB in whole cells and bacterial supernatants confirmed the negative regulatory activity of Rnr on T3SS effectors. We found that besides HNS and Ler, twenty-six other transcriptional regulators were also under Rnr control. Most importantly, the deletion of aar in EAEC or rnr in EPEC increases the adherence of these pathogens to human intestinal organoids. In contrast, the overexpression of ANR drastically reduces bacterial adherence and the formation of AE lesions in the intestine. Our study suggests a conserved regulatory mechanism and a central role of ANR in modulating intestinal colonization by these enteropathogens despite the fact that EAEC and EPEC evolved with utterly different virulence programs.

Structural and functional characterization of colonization factors AIBI-CS6 and AIIBII-CS6 of enterotoxigenic Escherichia coli

Over time, the structure and function of the broadly dispersed colonization factor (CF) CS6 of enterotoxigenic Escherichia coli (ETEC) have become more significant. CS6 is composed of tightly-associated subunits, CssA and CssB which due to presence of natural point mutation gave rise to CS6 subtypes. In contrast to the other ETEC CFs, CS6 is an afimbrial, spherical-shaped oligomers of (CssA-CssB)_n complex where 'n' is concentration dependent. In this study, we have compared AIBI-CS6 and AIIBII-CS6 structurally and functionally. The M_w of CssAI was 18.5 kDa but M_w of CssAII was 15.1 kDa. Both CssBI and CssBII had M_w of 15.9 kDa. The substitution of Gly³⁹ with Ala³⁹ in CssAI leads to reduction in Mw from 18.5 to 15.1 kDa. Due to higher M_w of CssAI, the size of AIBI concentration-dependent oligomers should be higher. However, the M_w of AIIBII oligomers were higher and AIIBII also showed higher oligomeric forms compared to AIBI both in native PAGE and electron microscopy. The oligomers of both subtypes could withstand greater temperatures and denaturant concentrations. In terms of cellular response, the levels of inflammatory cytokines were significantly higher in case of AIBI-CS6 expressing ETEC as compared to AIIBII-CS6 expressing ETEC both in vitro and in vivo. When inflammatory cytokines were evaluated after infecting suckling mice with these ETEC strains, the results were consistent. In conclusion, even though there was subtle structural difference between AIBI-CS6 and AIIBII-CS6 due to natural point mutations but ETEC strains expressing these subtypes displayed great variability in pathogenicity.

Shigellosis in Southeast Asia: A systematic review and meta-analysis

BACKGROUND

Southeast Asia is attractive for tourism. Unfortunately, travelers to this region are at risk of becoming infected with Shigella. We conducted a meta-analysis to provide updates on Shigella prevalence in Southeast Asia, along with their serogroups and serotypes.

METHODS

We conducted a systematic search using PubMed, EMBASE, and Web of Science for peer-reviewed studies from 2000 to November 2022. We selected studies that detected Shigella in stools by culture or polymerase chain reaction (PCR). Two reviewers extracted the data using a standardized form and performed quality assessments using the Joanna Briggs Institute checklist. The random effects model was used to estimate the pooled prevalence of Shigella.

RESULTS

During our search, we identified 4376 studies. 29 studies (from six Southeast Asian countries) were included in the systematic review, 21 each in the meta-analysis of the prevalence of Shigella (Sample size: 109545) and the prevalence of Shigella serogroups. The pooled prevalence of Shigella was 4% (95% CI: 4-5%) among diarrhea cases. Shigella sonnei was the most abundant serogroup in Thailand (74%) and Vietnam (57%), whereas Shigella flexneri was dominant in Indonesia (72%) and Cambodia (71%). Shigella dysenteriae and Shigella boydii were uncommon (pooled prevalence of 1% each). The pooled prevalence of Shigella was 5% (95% CI: 4-6%) in children aged <5 years. The pooled prevalence showed a decreasing trend comparing data collected between 2000-2013 (5%; 95% CI: 4-6%) and between 2014-2022 (3%; 95% CI: 2-4%). Shigella prevalence was 6% in studies that included participants with mixed pathogens versus 3% in those without. Shigella flexneri serotype 2a was the most frequently isolated (33%), followed by 3a (21%), 1b (10%), 2b (3%), and 6 (3%).

CONCLUSIONS

This study provides compelling evidence for the development of effective Shigella vaccines for residents of endemic regions and travellers to these areas.

Management and Prevention of Traveler's Diarrhea: A Cross-Sectional Study on Knowledge, Attitudes, and Practices in Italian Occupational Physicians (2019 and 2022)

Even though Italian Occupational Physicians (OP) are increasingly involved in the managing of overseas workers, their knowledge, attitudes, and practices (KAP) in travel medicine are mostly undefined. We, therefore, permed a KAP study specifically targeting the management of travelers' diarrhea (TD) by OP. A total of 371 professionals (43.4% males; mean age 40.8 ± 10.9 years) completed in 2 rounds (2019 and 2022) a specifically designed web questionnaire that inquired participating OP on their knowledge status (KS), risk perception, and management of TD through pre- and post-travel advice and interventions. Multivariable odds ratios (aOR) for predictors of a better knowledge status were calculated through regression analysis. Eventually, the majority of participants (53.4%) had participated in the management of cases of TD in the previous months, but only 26.4% were reportedly involved in pre-travel consultations. The overall knowledge status was unsatisfying (potential range: 0-100%, actual average of the sample 59.6% ± 14.6), with substantial uncertainties in the management of antimicrobial treatment. Interestingly, only a small subset of participants had previously prescribed antimicrobial prophylaxis or treatment (3.5% and 1.9%, respectively). Main effectors of a better knowledge status were: having a background qualification in Hygiene and Public Health (aOR 14.769, 95%CI 5.582 to 39.073), having previously managed any case of (aOR 3.107, 95%CI 1.484 to 6.506), and having higher concern on TD, reported by acknowledging high frequency (aOR 8.579, 95%CI 3.383 to 21.756) and severity (aOR 3.386; 95%CI 1.741 to 6.585) of this disorder. As the adherence of participating OP to official recommendations for TD management was unsatisfying, continuous Education on Travel Medicine should be improved by sharing up-to-date official recommendations on appropriate treatment options for TD.

Frontiers in Shigella Vaccine Development

In recent years, there has been a resurgence of interest in the development of vaccines against Shigella driven by the growing awareness of the impact of this pathogen on global health [...]

Antimicrobial Efficacy of Green Synthesized Nanosilver with Entrapped Cinnamaldehyde against Multi-Drug-Resistant Enteroaggregative Escherichia coli in Galleria mellonella

The global emergence of antimicrobial resistance (AMR) needs no emphasis. In this study, the in vitro stability, safety, and antimicrobial efficacy of nanosilver-entrapped cinnamaldehyde (AgC) against multi-drug-resistant (MDR) strains of enteroaggregative Escherichia coli (EAEC) were investigated. Further, the in vivo antibacterial efficacy of AgC against MDR-EAEC was also assessed in Galleria mellonella larval model. In brief, UV-Vis and Fourier transform infrared (FTIR) spectroscopy confirmed effective entrapment of cinnamaldehyde with nanosilver, and the loading efficiency was estimated to be 29.50 ± 0.56%. The AgC was of crystalline form as determined by the X-ray diffractogram with a mono-dispersed spherical morphology of 9.243 ± 1.83 nm in electron microscopy. AgC exhibited a minimum inhibitory concentration (MIC) of 0.008−0.016 mg/mL and a minimum bactericidal concentration (MBC) of 0.008−0.032 mg/mL against MDR- EAEC strains. Furthermore, AgC was stable (high-end temperatures, proteases, cationic salts, pH, and host sera) and tested safe for sheep erythrocytes as well as secondary cell lines (RAW 264.7 and HEp-2) with no negative effects on the commensal gut lactobacilli. in vitro, time-kill assays revealed that MBC levels of AgC could eliminate MDR-EAEC infection in 120 min. In G. mellonella larvae, AgC (MBC values) increased survival, decreased MDR-EAEC counts (p < 0.001), had an enhanced immunomodulatory effect, and was tested safe to the host. These findings infer that entrapment enhanced the efficacy of cinnamaldehyde and AgNPs, overcoming their limitations when used individually, indicating AgC as a promising alternative antimicrobial candidate. However, further investigation in appropriate animal models is required to declare its application against MDR pathogens.

The Shigella Vaccines Pipeline

Shigella is the leading cause of global diarrheal deaths that currently lacks a licensed vaccine. Shigellosis drives antimicrobial resistance and leads to economic impact through linear growth faltering. Today, there is a robust pipeline of vaccines in clinical development which are broadly divided into parenteral glycoconjugate vaccines, consisting of O-antigen conjugated to carrier proteins, and oral live attenuated vaccines, which incorporate targeted genetic mutations seeking to optimize the balance between reactogenicity, immunogenicity and ultimately protection. Proof of efficacy has previously been shown with both approaches but for various reasons no vaccine has been licensed to date. In this report, we outline the requirements for a Shigella vaccine and describe the current pipeline in the context of the many candidates that have previously failed or been abandoned. The report refers to papers from individual vaccine developers in this special supplement of Vaccines which is focused on Shigella vaccines. Once readouts of safety and immunogenicity from current trials of lead candidate vaccines among the target population of young children in low- and middle-income countries are available, the likely time to licensure of a first Shigella vaccine will become clearer.

The role of CFA/I in adherence and toxin delivery by ETEC expressing multiple colonization factors in the human enteroid model

Enterotoxigenic Escherichia coli (ETEC) is a primary causative agent of diarrhea in travelers and young children in low-to-middle-income countries (LMICs). ETEC adhere to intestinal epithelia via colonization factors (CFs) and secrete heat-stable toxin (ST) and/or heat-labile toxin (LT), causing dysregulated cellular ion transport and water secretion. ETEC isolates often harbor genes encoding more than one CF that are targets as vaccine antigens. CFA/I is a major CF that is associated with ETEC that causes moderate-to-severe diarrhea and plays an important role in pathogenesis. The Global Enteric Multicenter Study finding that 78% of CFA/I-expressing ETEC also encode the minor CF CS21 prompted investigation of the combined role of these two CFs. Western blots and electron microscopy demonstrated growth media-dependent and strain-dependent differences in CFA/I and CS21 expression. The critical role of CFA/I in adherence by ETEC strains expressing CFA/I and CS21 was demonstrated using the human enteroid model and a series of CFA/I- and CS21-specific mutants. Furthermore, only anti-CFA/I antibodies inhibited adherence by global ETEC isolates expressing CFA/I and CS21. Delivery of ST and resulting cGMP secretion was measured in supernatants from infected enteroid monolayers, and strain-specific ST delivery and time-dependent cGMP production was observed. Interestingly, cGMP levels were similar across wildtype and CF-deficient strains, reflecting a limitation of this static aerobic infection model. Despite adherence by ETEC and delivery of ST, the enteroid monolayer integrity was not disrupted, as shown by the lack of decrease in transepithelial electrical resistance and the lack of IL-8 cytokines produced during infection. Taken together, these data demonstrate that targeting CFA/I in global clinical CFA/I-CS21 strains is sufficient for adherence inhibition, supporting a vaccine strategy that focuses on blocking major CFs. In addition, the human enteroid model has significant utility for the study of ETEC pathogenesis and evaluation of vaccine-induced functional antibody responses.