Resistant pathogens as causes of traveller's diarrhea globally and impact(s) on treatment failure and recommendations

Bioactivity and efficacy of a hyperimmune bovine colostrum product- Travelan, against shigellosis in a non-Human primate model (Macaca mulatta)

Infectious diarrhea is a World Health Organization public health priority area due to the lack of effective vaccines and an accelerating global antimicrobial resistance crisis. New strategies are urgently needed such as immunoprophylactic for prevention of diarrheal diseases. Hyperimmune bovine colostrum (HBC) is an established and effective prophylactic for infectious diarrhea. The commercial HBC product, Travelan® (Immuron Ltd, Australia) targets multiple strains of enterotoxigenic Escherichia coli (ETEC) is highly effective in preventing diarrhea in human clinical studies. Although Travelan® targets ETEC, preliminary studies suggested cross-reactivity with other Gram-negative enteric pathogens including Shigella and Salmonella species. For this study we selected an invasive diarrheal/dysentery-causing enteric pathogen, Shigella, to evaluate the effectiveness of Travelan®, both in vitro and in vivo. Here we demonstrate broad cross-reactivity of Travelan® with all four Shigella spp. (S. flexneri, S. sonnei, S. dysenteriae and S. boydii) and important virulence factor Shigella antigens. Naïve juvenile rhesus macaques (NJRM) were randomized, 8 dosed with Travelan® and 4 with a placebo intragastrically twice daily over 6 days. All NJRM were challenged with S. flexneri 2a strain 2457T on the 4th day of treatment and monitored for diarrheal symptoms. All placebo-treated NJRM displayed acute dysentery symptoms within 24-36 hours of challenge. Two Travelan®-treated NJRM displayed dysentery symptoms and six animals remained healthy and symptom-free post challenge; resulting in 75% efficacy of prevention of shigellosis (p = 0.014). These results strongly indicate that Travelan® is functionally cross-reactive and an effective prophylactic for shigellosis. This has positive implications for the prophylactic use of Travelan® for protection against both ETEC and Shigella spp. diarrheal infections. Future refinement and expansion of pathogens recognized by HBC including Travelan® could revolutionize current management of gastrointestinal infections and outbreaks in travelers' including military, peacekeepers, humanitarian workers and in populations living in endemic regions of the world.

A broadly immunogenic polyvalent Shigella multiepitope fusion antigen protein protects against Shigella sonnei and Shigella flexneri lethal pulmonary challenges in mice

There are no licensed vaccines for Shigella, a leading cause of children's diarrhea and a common etiology of travelers' diarrhea. To develop a cross-protective Shigella vaccine, in this study, we constructed a polyvalent protein immunogen to present conserved immunodominant epitopes of Shigella invasion plasmid antigens B (IpaB) and D (IpaD), VirG, GuaB, and Shiga toxins on backbone protein IpaD, by applying an epitope- and structure-based multiepitope-fusion-antigen (MEFA) vaccinology platform, examined protein (Shigella MEFA) broad immunogenicity, and evaluated antibody function against Shigella invasion and Shiga toxin cytotoxicity but also protection against Shigella lethal challenge. Mice intramuscularly immunized with Shigella MEFA protein developed IgG responses to IpaB, IpaD, VirG, GuaB, and Shiga toxins 1 and 2; mouse sera significantly reduced invasion of Shigella sonnei, Shigella flexneri serotype 2a, 3a, or 6, Shigella boydii, and Shigella dysenteriae type 1 and neutralized cytotoxicity of Shiga toxins of Shigella and Shiga toxin-producing Escherichia coli in vitro. Moreover, mice intranasally immunized with Shigella MEFA protein (adjuvanted with dmLT) developed antigen-specific serum IgG, lung IgG and IgA, and fecal IgA antibodies, and survived from lethal pulmonary challenge with S. sonnei or S. flexneri serotype 2a, 3a, or 6. In contrast, the control mice died, became unresponsive, or lost 20% of body weight in 48 h. These results indicated that this Shigella MEFA protein is broadly immunogenic, induces broadly functional antibodies, and cross-protects against lethal pulmonary challenges with S. sonnei or S. flexneri serotypes, suggesting a potential application of this polyvalent MEFA protein in Shigella vaccine development.

Antimicrobial-Resistant Nontyphoidal Salmonella Infection Following International Travel-United States, 2018-2019

BACKGROUND

Antimicrobial resistance in nontyphoidal Salmonella (NTS) can limit treatment options. We assessed the contribution of international travel to antimicrobial-resistant NTS infections.

METHODS

We describe NTS infections that were reported to the Foodborne Diseases Active Surveillance Network during 2018-2019 and screened for genetic resistance determinants, including those conferring decreased susceptibility to first-line agents (ciprofloxacin, ceftriaxone, or azithromycin). We used multivariable logistic regression to assess the association between resistance and international travel during the 7 days before illness began. We estimated the contribution of international travel to resistance using population-attributable fractions, and we examined reported antimicrobial use.

RESULTS

Among 9301 NTS infections, 1159 (12%) occurred after recent international travel. Predicted resistance to first-line antimicrobials was more likely following travel; the adjusted odds ratio varied by travel region and was highest after travel to Asia (adjusted odds ratio, 7.2 [95% confidence interval, 5.5-9.5]). Overall, 19% (95% confidence interval, 17%-22%) of predicted resistance to first-line antimicrobials was attributable to international travel. More travelers than nontravelers receiving ciprofloxacin or other fluoroquinolones had isolates with predicted resistance to fluoroquinolones (29% vs 9%, respectively; P < .01).

CONCLUSIONS

International travel is a substantial risk factor for antimicrobial-resistant NTS infections. Understanding risks of resistant infection could help target prevention efforts.

Antibiotic resistance trends for common bacterial aetiologies of childhood diarrhoea in low- and middle-income countries: A systematic review

Background

Diarrhoea is the second most common cause of death among children under the age of five worldwide. The World Health Organization (WHO) recommends treating diarrhoea with oral rehydration therapy, intravenous fluids for severe dehydration, and zinc supplements. Antibiotics are only recommended to treat acute, invasive diarrhoea. Rising antibiotic resistance has led to a decrease in the effectiveness of treatments for diarrhoea.

Methods

A systematic literature review in PubMed, Web of Science, and EMBASE was conducted to identify articles relevant to antibiotic-resistant childhood diarrhoea. Articles in English published between 1990 to 2020 that described antibiotic resistance patterns of common pathogens causing childhood diarrhoea in low- and middle-income countries were included. The studies were limited to papers that categorized children as 0-5 years or 0-10 years old. The proportion of isolates with resistance to major classes of antibiotics stratified by major WHO global regions and time was determined.

Results

Quantitative data were extracted from 44 articles that met screening criteria; most focused on children under five years. Escherichia coli isolates had relatively high resistance rates to ampicillin and tetracycline in the African (AFR), American (AMR), and Eastern Mediterranean Regions (EMR). There was moderate to high resistance to ampicillin and third generation cephalosporins among Salmonella spp in the AFR, EMR, and the Western Pacific Region (WPR). Resistance rates for ampicillin, co-trimoxazole, and chloramphenicol for Shigella in the AFR started at an alarmingly high rate ( ~ 90%) in 2006 and fluctuated over time. There were limited antibiotic resistance data for Aeromonas, Yersinia, and V. cholerae. The 161 isolates of Campylobacter analysed showed initially low rates of fluoroquinolone resistance with high rates of resistance in recent years, especially in the Southeast Asian Region.

Conclusions

Resistance to inexpensive antibiotics for treatment of invasive diarrhoea in children under ten years is widespread (although data on 6- to 10-year-old children are limited), and resistance rates to fluoroquinolones and later-generation cephalosporins are increasing. A strong regional surveillance system is needed to carefully monitor trends in antibiotic resistance, future studies should include school-aged children, and interventions are needed to reduce inappropriate use of antibiotics for the treatment of community-acquired, non-invasive diarrhoea.

Registration

This systematic review was registered in Prospero (registration number CRD42020204004) in August 2020.

Conditions Necessary for the Transfer of Antimicrobial Resistance in Poultry Litter

Animal manures contain a large and diverse reservoir of antimicrobial resistance (AMR) genes that could potentially spillover into the general population through transfer of AMR to antibiotic-susceptible pathogens. The ability of poultry litter microbiota to transmit AMR was examined in this study. Abundance of phenotypic AMR was assessed for litter microbiota to the antibiotics: ampicillin (Ap; 25 μg/mL), chloramphenicol (Cm; 25 μg/mL), streptomycin (Sm; 100 μg/mL), and tetracycline (Tc; 25 μg/mL). qPCR was used to estimate gene load of streptomycin-resistance and sulfonamide-resistance genes aadA1 and sul1, respectively, in the poultry litter community. AMR gene load was determined relative to total bacterial abundance using 16S rRNA qPCR. Poultry litter contained 10⁸ CFU/g, with Gram-negative enterics representing a minor population (<10⁴ CFU/g). There was high abundance of resistance to Sm (10⁶ to 10⁷ CFU/g) and Tc (10⁶ to 10⁷ CFU/g) and a sizeable antimicrobial-resistance gene load in regards to gene copies per bacterial genome (aadA1: 0.0001-0.0060 and sul1: 0.0355-0.2455). While plasmid transfer was observed from Escherichia coli R100, as an F-plasmid donor control, to the Salmonella recipient in vitro, no AMR Salmonella were detected in a poultry litter microcosm with the inclusion of E. coli R100. Confirmatory experiments showed that isolated poultry litter bacteria were not interfering with plasmid transfer in filter matings. As no R100 transfer was observed at 25 °C, conjugative plasmid pRSA was chosen for its high plasmid transfer frequency (10^-4 to 10^-5) at 25 °C. While E. coli strain background influenced the persistence of pRSA in poultry litter, no plasmid transfer to Salmonella was ever observed. Although poultry litter microbiota contains a significant AMR gene load, potential to transmit resistance is low under conditions commonly used to assess plasmid conjugation.

Toward a Shigella Vaccine: Opportunities and Challenges to Fight an Antimicrobial-Resistant Pathogen

Shigellosis causes more than 200,000 deaths worldwide and most of this burden falls on Low- and Middle-Income Countries (LMICs), with a particular incidence in children under 5 years of age. In the last decades, Shigella has become even more worrisome because of the onset of antimicrobial-resistant strains (AMR). Indeed, the WHO has listed Shigella as one of the priority pathogens for the development of new interventions. To date, there are no broadly available vaccines against shigellosis, but several candidates are being evaluated in preclinical and clinical studies, bringing to light very important data and information. With the aim to facilitate the understanding of the state-of-the-art of Shigella vaccine development, here we report what is known about Shigella epidemiology and pathogenesis with a focus on virulence factors and potential antigens for vaccine development. We discuss immunity after natural infection and immunization. In addition, we highlight the main characteristics of the different technologies that have been applied for the development of a vaccine with broad protection against Shigella.

Burden of Shigella in South Asia: a systematic review and meta-analysis

BACKGROUND

Shigella remains one of the most common causes of diarrhoea in South Asia. Current estimates of the prevalence of Shigella are critical for guiding control measures. We estimated the prevalence of Shigella species and serogroups in South Asia.

METHODS

We performed a systematic review using PubMed, EMBASE, Google Scholar and Web of Science for peer-reviewed studies published between 2000 and 19 June 2022. We also manually searched the reference lists of the reviewed studies to identify additional studies. We included studies that detected the presence of Shigella in stool by culture or polymerase chain reaction (PCR). Studies associated with outbreaks were excluded. Two investigators independently reviewed the studies, extracted the data and performed quality assessment. A random-effects meta-analysis was performed to determine the pooled prevalence of Shigella.

RESULTS

Our search yielded 5707 studies, of which 91 studies from five South Asian countries were included in the systematic review, 79 in the meta-analysis of Shigella prevalence and 63 in the meta-analysis of Shigella serogroups prevalence. The pooled prevalence of Shigella was 7% [95% confidence interval (CI): 6-7%], with heterogeneity (I2 = 98.7; P < 0.01). The prevalence of Shigella was higher in children aged <5 years (10%; 95% CI: 8-11%), in rural areas (12%; 95% CI: 10-14%) and in studies using PCR (15%; 95% CI: 11-19%). Shigella flexneri (58%) was the most abundant serogroup, followed by Shigella sonnei (19%), Shigella boydii (10%) and Shigella dysenteriae (9%). Shigella flexneri 2a was the most frequently isolated serotype (36%), followed by serotype 3a (12%), serotype 6 (12%) and serotype 1b (6%). The prevalence of non-typeable Shigella was 10.0%.

CONCLUSIONS

Although the prevalence of Shigella in South Asia remains generally high, it varies by age group and geographical area, with data lacking in some countries. Effective Shigella vaccines would be advantageous for both endemic communities and travellers.

Dual-Use Vaccine for Diarrhoeal Diseases: Cross-Protective Immunogenicity of a Cold-Chain-Free, Live-Attenuated, Oral Cholera Vaccine against Enterotoxigenic Escherichia coli (ETEC) Challenge in BALB/c Mice

In low- and middle-income countries, diarrhoeal diseases are the second most common cause of mortality in children, mainly caused by enterotoxin-producing bacteria, such as Shigella, Vibrio, Salmonella, and Escherichia coli. Cholera and traveller's diarrhoea are caused by Vibrio cholerae (O1 and O139 serogroups) and enterotoxigenic Escherichia coli (ETEC), respectively. The cholera toxin (CT) produced by V. cholerae and the heat-labile enterotoxin (LT) of ETEC are closely related by structure, function, and the immunological response to them. There is no exclusive vaccine for ETEC; however, cholera vaccines based on the CT-B component elicit a short-term cross-protection against ETEC infection. In this context, the cross-protective efficacy of MyChol^TM, a prototype cold-chain-free, live-attenuated, oral cholera vaccine against V. cholerae O139 was evaluated in BALB/c mice. The 100% lethal dose (LD₁₀₀) of 10⁹ CFU/mL of the ETEC H10407 strain was used for the challenge studies. The mice immunised with MyChol™ survived the challenge by producing anti-CT antibodies, which cross-neutralised the LT toxin with no body weight loss and no sign of diarrhoea. Compared to unimmunised mice, the immunised mice elicited the neutralising antitoxin that markedly decreased ETEC colonisation and fluid accumulation caused by ETEC H10407 in the intestines. The immunised mice recorded higher antibody titres, including anti-CT IgG, anti-LT IgG, anti-CT-B IgG, and anti-LTB IgG. Only a two-fold rise in anti-CT/CT-B/LT/LT-B IgA was recorded in serum samples from immunised mice. No bactericidal antibodies against ETEC H10407 were detected. This investigation demonstrates the safety, immunogenicity, and cross-protective efficacy of MyChol^TM against the ETEC H10407 challenge in BALB/c mice.

Antimicrobial resistance of enteric pathogens in the Military Health System, 2009 - 2019

BACKGROUND

Acute diarrhea (AD) can have significant impacts on military troop readiness. Medical providers must understand current trends of enteropathogen antimicrobial resistance (AMR) in service members (SMs) to inform proper, timely treatment options. However, little is known of enteric pathogen profiles across the Military Health System (MHS). The primary objectives of this study were to identify gaps in enteric pathogen surveillance within the MHS, describe the epidemiology of AMR in enteric pathogens, and identify trends across the MHS both within the Continental United States (CONUS) and outside of the Continental United States (OCONUS).

METHODS

Health Level 7 (HL7)-formatted laboratory data were queried for all specimens where Salmonella, Shigella, and Campylobacter species, as well as Shiga toxin-producing Escherichia coli (E. coli) (STEC) were isolated and certified between 1 January 2009 - 31 December 2019. Antibiotic susceptibility testing (AST) results were queried and summarized where available. Descriptive statistics were calculated for each organism by specimen source, year, and susceptibility testing availability.

RESULTS

Among a total of 13,852 enteric bacterial isolates, 11,877 (86%) were submitted from CONUS locations. Out of 1479 Shigella spp. and 6755 Salmonella spp. isolates, 1221 (83%) and 5019 (74%), respectively, reported any susceptibility results through the MHS. Overall, only 15% of STEC and 4% of Campylobacter spp. specimens had AST results available. Comparing AST reporting at CONUS versus OCONUS locations, AST was reported for 1175 (83%) and 46 (78%) of Shigella isolates at CONUS and OCONUS locations, respectively, and for 4591 (76%) and 428 (63%) of Salmonella isolates at CONUS and OCONUS locations, respectively.

CONCLUSIONS

This study revealed inconsistent enteropathogen AST conducted across the MHS, with differing trends between CONUS and OCONUS locations. Additional work is needed to assess pathogen-specific gaps in testing and reporting to develop optimal surveillance that supports the health of the force.

Field evaluation of a novel, rapid diagnostic assay, and molecular epidemiology of enterotoxigenic E. coli among Zambian children presenting with diarrhea

Background

Enterotoxigenic Escherichia coli (ETEC) is one of the top aetiologic agents of diarrhea in children under the age of 5 in low-middle income countries (LMICs). The lack of point of care diagnostic tools for routine ETEC diagnosis results in limited data regarding the actual burden and epidemiology in the endemic areas. We evaluated performance of the novel Rapid LAMP based Diagnostic Test (RLDT) for detection of ETEC in stool as a point of care diagnostic assay in a resource-limited setting.

Methods

We conducted a cross-sectional study of 324 randomly selected stool samples from children under 5 presenting with moderate to severe diarrhea (MSD). The samples were collected between November 2012 to September 2013 at selected health facilities in Zambia. The RLDT was evaluated by targeting three ETEC toxin genes [heat labile toxin (LT) and heat stable toxins (STh and STp)]. Quantitative PCR was used as the “gold standard” to evaluate the diagnostic sensitivity and specificity of RLDT for detection of ETEC. We additionally described the prevalence and seasonality of ETEC.

Results

The study included 324 participants, 50.6% of which were female. The overall prevalence of ETEC was 19.8% by qPCR and 19.4% by RLDT. The children between 12 to 59 months had the highest prevalence of 22%. The study determined ETEC toxin distribution was LT 28/321(9%), ST 18/321(6%) and LT/ST 16/321(5%). The sensitivity and specificity of the RLDT compared to qPCR using a Ct 35 as the cut-off, were 90.7% and 97.5% for LT, 85.2% and 99.3% for STh and 100% and 99.7% for STp, respectively.

Conclusion

The results of this study suggest that RLDT is sufficiently sensitive and specific and easy to implement in the endemic countries. Being rapid and simple, the RLDT also presents as an attractive tool for point-of-care testing at the health facilities and laboratories in the resource-limited settings.

ETEC is one of the top causes of diarrheal diseases in low and middle income countries. The advancement of molecular diagnosis has made it possible to accurately detect ETEC in endemic areas. However, the complexity, infrastructure and cost implication of these tests has made it a challenge to routinely incorporate them in health facilities in endemic settings. The ETEC RLDT is a simple and cost-effective molecular tool that can be used to screen for ETEC in resource limited settings. Here, we described the performance of the RLDT against a qPCR as the gold standard. Our findings showed that the ETEC RLDT performs comparable to the qPCR and would be a suitable screening tool in health facilities in recourse limited settings.

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.

Extended-spectrum beta-lactamase-producing strains among diarrhoeagenic Escherichia coli-prospective traveller study with literature review

BACKGROUND

Antibiotics are no longer the primary approach for treating all travellers' diarrhoea (TD): most cases resolve without antibiotics and using them predisposes to colonization by multidrug-resistant bacteria. Data are accumulating on increasing resistance among TD pathogens, yet research into the most common agents, diarrhoeagenic Escherichia coli (DEC), remains limited.

METHODS

A total of 413 travellers to the (sub)tropics were analyzed for travel-acquired diarrhoeal pathogens and ESBL-PE. To identify ESBL-producing DEC, ESBL-producing E. coli (ESBL-EC) isolates were subjected to multiplex qPCR for various DEC pathotypes: enteroaggregative (EAEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), enteroinvasive (EIEC) and enterohaemorrhagic (EHEC) E. coli.For a literature review, we screened studies among travellers and locals in low- and middle-income countries (LMICs) on the frequency of ESBL-producing DEC, and among travellers, also DEC with resistance to ciprofloxacin, azithromycin, and rifamycin derivatives.

RESULTS

Our rate of ESBL-EC among all DEC findings was 2.7% (13/475); among EAEC 5.7% (10/175), EPEC 1.1% (2/180), ETEC 1.3% (1/80) and EHEC (0/35) or EIEC 0% (0/5). The literature search yielded three studies reporting ESBL-EC frequency and thirteen exploring resistance to TD antibiotics among travel-acquired DEC. For EAEC and ETEC, the ESBL-EC rates were 10-13% and 14-15%, resistance to fluoroquinolones 0-42% and 0-40%, azithromycin 0-29% and 0-61%, and rifaximin 0% and 0-20%. The highest rates were from the most recent collections. Proportions of ESBL-producing DEC also appear to be increasing among locals in LMICs and even carbapenemase-producing DEC were reported.

CONCLUSION

ESBL producers are no longer rare among DEC, and the overall resistance to various antibiotics is increasing. The data predict decreasing efficacy of antibiotic treatment, threatening its benefits, for disadvantages still prevail when efficacy is lost.

What's new in travellers' diarrhoea: updates on epidemiology, diagnostics, treatment and long-term consequences

BACKGROUND

Travellers' diarrhoea (TD) is the most common clinical syndrome affecting travellers. This narrative review summarizes key discoveries reported in the last two years related to TD and suggests areas for future research.

METHODS

A PubMed literature search was conducted for novel data in TD research published between 12 January 2018 and 12 January 2020. Inclusion was based on contribution to epidemiology, aetiology, diagnostics, management and long-term consequences and relevance to public health, discovery and clinical practice.

RESULTS

The initial literature search yielded 118 articles. We retrieved 72 and reviewed 31 articles for inclusion. The findings support our understanding that TD incidence varies by traveller group and environment with students and military-travel remaining moderately high risk, and control of food and water in mass gathering events remain an important goal. The growth of culture-independent testing has led to a continued detection of previously known pathogens, but also an increased detection frequency of norovirus. Another consequence is the increase in multi-pathogen infections, which require consideration of clinical, epidemiological and diagnostic data. Fluoroquinolone resistant rates continue to rise. New data on non-absorbable antibiotics continue to emerge, offering a potential alternative to current recommendations (azithromycin and fluoroquinolones), but are not recommended for febrile diarrhoea or dysentery or regions/itineraries where invasive pathogens are likely to cause illness. Recent studies investigated the interaction of the microbiome in TD prevention and consequences, and while discriminating features were identified, much uncertainty remains. The prevalence of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) acquisition and carriage is increasing. Finally, continued research documents the post-infectious consequences, whereas mechanisms of reactive arthritis and post-infectious IBS necessitate further investigation.

CONCLUSIONS

Globally, TD remains an important travel health issue and advances in our understanding continue. More research is needed to mitigate risk factors where possible and develop risk-based management strategies to reduce antibiotic usage and its attendant consequences.

Molecular Detection of Colistin Resistance mcr-1 Gene in Multidrug-Resistant Escherichia coli Isolated from Chicken

Zoonotic and antimicrobial-resistant Escherichia coli (hereafter, E. coli) is a global public health threat which can lead to detrimental effects on human health. Here, we aim to investigate the antimicrobial resistance and the presence of mcr-1 gene in E. coli isolated from chicken feces. Ninety-four E. coli isolates were obtained from samples collected from different locations in Bangladesh, and the isolates were identified using conventional microbiological tests. Phenotypic disk diffusion tests using 20 antimicrobial agents were performed according to CLSI-EUCAST guidelines, and minimum inhibitory concentrations (MICs) were determined for a subset of samples. E. coli isolates showed high resistance to colistin (88.30%), ciprofloxacin (77.66%), trimethoprim/sulfamethoxazole (76.60%), tigecycline (75.53%), and enrofloxacin (71.28%). Additionally, the pathotype eaeA gene was confirmed in ten randomly selected E. coli isolates using primer-specific polymerase chain reaction (PCR). The presence of mcr-1 gene was confirmed using PCR and sequencing analysis in six out of ten E. coli isolates. Furthermore, sequencing and phylogenetic analyses revealed a similarity between the catalytic domain of Neisseria meningitidis lipooligosaccharide phosphoethanolamine transferase A (LptA) and MCR proteins, indicating that the six tested isolates were colistin resistant. Finally, the findings of the present study showed that E. coli isolated from chicken harbored mcr-1 gene, and multidrug and colistin resistance. These findings accentuate the need to implement strict measures to limit the imprudent use of antibiotics, particularly colistin, in agriculture and poultry farms.

Multidrug-Resistant Lineage of Enterotoxigenic Escherichia coli ST182 With Serotype O169:H41 in Airline Waste

Enterotoxigenic Escherichia coli (ETEC) is the primary aetiologic agent of traveller’s diarrhoea and a significant cause of diarrhoeal disease and death in developing countries. ETEC O169:H41 strains are known to cause both traveller’s diarrhoea and foodborne outbreaks in developed countries and are cause for concern. Here, whole-genome sequencing (WGS) was used to assemble 46 O169:H41 (ST182) E. coli draft genomes derived from two airplane waste samples sourced from a German international airport. The ST182 genomes were compared with all 84 publicly available, geographically diverse ST182 genomes to construct a core genome-based phylogenetic tree. ST182 isolates were all phylogroup E, the majority serotype O169:H41 (n = 121, 93%) and formed five major clades. The airplane waste isolates differed by an average of 15 core SNPs (range 0–45) but their accessory genome content was diverse. While uncommon in other ST182 genomes, all airplane-derived ST182 isolates carried: (i) extended-spectrum β-lactamase gene bla_CTX–M–15 notably lacking the typical adjacent ISEcp1; (ii) qnrS1 and the S83L mutation in gyrA, both conferring resistance to fluoroquinolones; and (iii) a class 1 integron structure (IS26-intI1_Δ648-dfrA17-aadA5-qacEΔ1-sul1-ORF-srpC-padR-IS6100-mphR-mrx-mphA-IS26) identified previously in major extraintestinal pathogenic E. coli STs but not in ETEC. ST182 isolates carried ETEC-specific virulence factors STp + CS6. Adhesin/invasin tia was identified in 89% of aircraft ST182 isolates (vs 23%) and was located on a putative genomic island within a hotspot region for various insertions including PAI I₅₃₆ and plasmid-associated transposons. The most common plasmid replicons in this collection were IncFII (100%; F2:A-:B-) and IncB/O/K/Z (89%). Our data suggest that potentially through travel, E. coli ST182 are evolving a multidrug-resistant profile through the acquisition of class 1 integrons and different plasmids.

Pharmaceutical Approaches on Antimicrobial Resistance: Prospects and Challenges

The rapid increase in pathogenic microorganisms with antimicrobial resistant profiles has become a significant public health problem globally. The management of this issue using conventional antimicrobial preparations frequently results in an increase in pathogen resistance and a shortage of effective antimicrobials for future use against the same pathogens. In this review, we discuss the emergence of AMR and argue for the importance of addressing this issue by discovering novel synthetic or naturally occurring antibacterial compounds and providing insights into the application of various drug delivery approaches, delivered through numerous routes, in comparison with conventional delivery systems. In addition, we discuss the effectiveness of these delivery systems in different types of infectious diseases associated with antimicrobial resistance. Finally, future considerations in the development of highly effective antimicrobial delivery systems to combat antimicrobial resistance are presented.

Preclinical Characterization of Immunogenicity and Efficacy against Diarrhea from MecVax, a Multivalent Enterotoxigenic E. coli Vaccine Candidate

There are no vaccines licensed for enterotoxigenic Escherichia coli (ETEC), a leading cause of diarrhea for children in developing countries and international travelers. Virulence heterogeneity among strains and difficulties identifying safe antigens for protective antibodies against STa, a potent but poorly immunogenic heat-stable toxin which plays a key role in ETEC diarrhea, are challenges in ETEC vaccine development. To overcome these challenges, we applied a toxoid fusion strategy and a novel epitope- and structure-based multiepitope fusion antigen (MEFA) vaccinology platform to construct two chimeric multivalent proteins, toxoid fusion 3xSTa_N12S-mnLT_R192G/L211A and adhesin CFA/I/II/IV MEFA, and demonstrated that the proteins induced protective antibodies against STa and heat-labile toxin (LT) produced by all ETEC strains or the seven most important ETEC adhesins (CFA/I and CS1 to CS6) expressed by the ETEC strains causing 60 to 70% of diarrheal cases and moderate to severe cases. Combining two proteins, we prepared a protein-based multivalent ETEC vaccine, MecVax. MecVax was broadly immunogenic; mice and pigs intramuscularly immunized with MecVax developed no apparent adverse effects but had robust antibody responses to the target toxins and adhesins. Importantly, MecVax-induced antibodies were broadly protective, demonstrated by significant adherence inhibition against E. coli bacteria producing any of the seven adhesins and neutralization of STa and cholera toxin (CT) enterotoxicity. Moreover, MecVax protected against watery diarrhea and provided over 70% and 90% protection against any diarrhea from an STa-positive or an LT-positive ETEC strain in a pig challenge model. These results indicated that MecVax induces broadly protective antibodies and prevents diarrhea preclinically, signifying that MecVax is potentially an effective injectable vaccine for ETEC. IMPORTANCE Enterotoxigenic Escherichia coli (ETEC) bacteria are a top cause of children's diarrhea and travelers' diarrhea and are responsible for over 220 million diarrheal cases and more than 100,000 deaths annually. A safe and effective ETEC vaccine can significantly improve public health, particularly in developing countries. Data from this preclinical study showed that MecVax induces broadly protective antiadhesin and antitoxin antibodies, becoming the first ETEC vaccine candidate to induce protective antibodies inhibiting adherence of the seven most important ETEC adhesins and neutralizing the enterotoxicity of not only LT but also STa toxin. More importantly, MecVax is shown to protect against clinical diarrhea from STa-positive or LT-positive ETEC infection in a pig challenge model, recording protection from antibodies induced by the protein-based, injectable, subunit vaccine MecVax against ETEC diarrhea and perhaps the possibility of intramuscularly administered protein vaccines for protection against intestinal mucosal infection.

Glycoconjugate vaccines against Salmonella enterica serovars and Shigella species: existing and emerging methods for their analysis

The global spread of enteric disease, the increasingly limited options for antimicrobial treatment and the need for effective eradication programs have resulted in an increased demand for glycoconjugate enteric vaccines, made with carbohydrate-based membrane components of the pathogen, and their precise characterisation. A set of physico-chemical and immunological tests are employed for complete vaccine characterisation and to ensure their consistency, potency, safety and stability, following the relevant World Health Organization and Pharmacopoeia guidelines. Variable requirements for analytical methods are linked to conjugate structure, carrier protein nature and size and O-acetyl content of polysaccharide. We investigated a key stability-indicating method which measures the percent free saccharide of Salmonella enterica subspecies enterica serovar Typhi capsular polysaccharide, by detergent precipitation, depolymerisation and HPAEC-PAD quantitation. Together with modern computational approaches, a more precise design of glycoconjugates is possible, allowing for improvements in solubility, structural conformation and stability, and immunogenicity of antigens, which may be applicable to a broad spectrum of vaccines. More validation experiments are required to establish the most effective and suitable methods for glycoconjugate analysis to bring uniformity to the existing protocols, although the need for product-specific approaches will apply, especially for the more complex vaccines. An overview of current and emerging analytical approaches for the characterisation of vaccines against Salmonella Typhi and Shigella species is described in this paper. This study should aid the development and licensing of new glycoconjugate vaccines aimed at the prevention of enteric diseases.

The design of multiepitope vaccines from plasmids of diarrheagenic Escherichia coli against diarrhoea infection: Immunoinformatics approach

Diarrhoea infection is a major global health public problem and is caused by many organisms including diarrheagenic Escherichia coli pathotypes. The common problem with diarrhoea is the drug resistance of pathogenic bacteria, the most promising alternative means of preventing drug resistance is vaccination. However, there has not been any significant success in the prevention of diarrhoea caused by E. coli through vaccination. Epitope-based vaccine is gaining more attention due to its safety and specificity. Sequence variation of protective antigens of the pathogen has posed a new challenge in the development of epitope-based vaccines against the infection, leading to the necessity of multiepitope based design. In this study, immunoinformatics tools were used to design multiepitope vaccine candidates from plasmid genome sequences of multiple pathotypes of E. coli species involved in diarrhoea infections. The ability of the identified epitopes to be used as a cross-protect multiepitope vaccine was achieved by identifying conserved, immunogenic and antigenic peptides that can elicit CD4⁺ T-cell, CD8⁺ T-cell and B-cell and bind to MHC I and II HLA alleles. The molecular docking results of T-cell epitopes showed their well binding affinity to receptive protein and with a wider population coverage. The different multiepitope-based vaccines (MEVCs) candidates were constructed and based on the types of epitope linker they contained. The MEVCs exhibited very good binding interactions with the human immune receptor. Among multiepitope vaccines constructed, MEVC6, MEVCA and MEVCB are more promising as potential vaccine candidates for cross-protection against gastrointestinal infections according to the computational study. It is also hoped that after validation and testing, the predicted multiepitope-based vaccine candidates will probably resolve the challenge of immunological heterogeneity facing enteric vaccine development.

Antifungal activity and antidiarrheal activity via antimotility mechanisms of (-)-fenchone in experimental models

BACKGROUND

(-)-Fenchone is a bicyclic monoterpene present in essential oils of plant species, such as Foeniculum vulgare and Peumus boldus, used to treatment of gastrointestinal diseases. Pharmacological studies report its anti-inflammatory, antioxidant, and antinociceptive activity.

AIM

To investigate antidiarrheal activity related to gastrointestinal motility, intestinal secretion and antimicrobial activity.

METHODS

A castor oil-induced diarrhea model was used to evaluate antidiarrheal activity. Intestinal transit and gastric emptying protocols were used to assess a possible antimotility effect. Muscarinic receptors, presynaptic α₂-adrenergic and tissue adrenergic receptors, K_ATP channels, nitric oxide were investigated to uncover antimotility mechanisms of action and castor oil-induced enteropooling to elucidate antisecretory mechanisms. The antimicrobial activity was evaluated in the minimum inhibitory concentration model, the fractional inhibitory concentration index using the (-)-fenchone association method with standard antifungal agents.

RESULTS

(-)-Fenchone (75, 150 and 300 mg/kg) showed antidiarrheal activity, with a significant decrease in the evacuation index. This activity is possibly related to a percentage of reduced intestinal transit (75, 150 and 300 mg/kg). The antimotility effect of (-)-fenchone decreased in the presence of pilocarpine, yohimbine, propranolol, L-NG-nitroarginine methyl ester or glibenclamide. In the enteropooling model, no reduction in intestinal fluid weight was observed. (-)- Fenchone did not show antibacterial activity; on the other hand, inhibits the growth of strains of fungi with a minimum fungicide concentration of 32 μg/mL. However, when it was associated with amphotericin B, no synergism was observed.

CONCLUSION

The antidiarrheal effect of (-)-fenchone in this study involves antimotility effect and not involve antisecretory mechanisms. (-)-Fenchone presents antifungal activity; however, it did not show antibacterial activity.

Characterization of ShigETEC, a Novel Live Attenuated Combined Vaccine against Shigellae and ETEC

Background: Shigella spp. and enterotoxigenic Escherichia coli (ETEC) remain the two leading bacterial causes of diarrheal diseases worldwide. Attempts to develop preventive vaccines against Shigella and ETEC have not yet been successful. The major challenge for a broad Shigella vaccine is the serotype-specific immune response to the otherwise protective LPS O-antigen. ETEC vaccines mainly rely on the heat-labile enterotoxin (LT), while heat-stable toxin (ST) has also been shown to be an important virulence factor. Methods: We constructed a combined Shigella and ETEC vaccine (ShigETEC) based on a live attenuated Shigella strain rendered rough and non-invasive with heterologous expression of two ETEC antigens, LTB and a detoxified version of ST (ST_N12S). This new vaccine strain was characterized and tested for immunogenicity in relevant animal models. Results: Immunization with ShigETEC resulted in serotype independent protection in the mouse lung shigellosis model and induced high titer IgG and IgA antibodies against bacterial lysates, and anti-ETEC toxin antibodies with neutralizing capacity. Conclusions: ShigETEC is a promising oral vaccine candidate against Shigella and ETEC infections and currently in Phase 1 testing.

Vaccines against gastroenteritis, current progress and challenges

Enteric viral and bacterial infections continue to be a leading cause of mortality and morbidity in young children in low-income and middle-income countries, the elderly, and immunocompromised individuals. Vaccines are considered an effective and practical preventive approach against the predominantly fecal-to-oral transmitted gastroenteritis particularly in the resource-limited countries or regions where implementation of sanitation systems and supply of safe drinking water are not quickly achievable. While vaccines are available for a few enteric pathogens including rotavirus and cholera, there are no vaccines licensed for many other enteric viral and bacterial pathogens. Challenges in enteric vaccine development include immunological heterogeneity among pathogen strains or isolates, a lack of animal challenge models to evaluate vaccine candidacy, undefined host immune correlates to protection, and a low protective efficacy among young children in endemic regions. In this article, we briefly updated the progress and challenges in vaccines and vaccine development for the leading enteric viral and bacterial pathogens including rotavirus, human calicivirus, Shigella, enterotoxigenic Escherichia coli (ETEC), cholera, nontyphoidal Salmonella, and Campylobacter, and introduced a novel epitope- and structure-based vaccinology platform known as MEFA (multiepitope fusion antigen) and the application of MEFA for developing broadly protective multivalent vaccines against heterogenous pathogens.

New and alternative strategies for the prevention, control, and treatment of antibiotic-resistant Campylobacter

Campylobacter is an enteric pathogen and a leading bacterial cause of diarrhea worldwide. It is widely distributed in food animal species and is transmitted to humans primarily through the foodborne route. While generally causing self-limited diarrhea in humans, Campylobacter may induce severe or systemic infections in immunocompromised or young/elderly patients, which often requires antibiotic therapy with the first-line antibiotics including fluoroquinolones and macrolides. Over the past decades, Campylobacter has acquired resistance to these clinically significant antibiotics, compromising the effectiveness of antibiotic treatments. To address this concern, many studies have been conducted to advance novel and alternative measures to control antibiotic-resistant Campylobacter in animal reservoirs and in the human host. Although some of these undertakings have yielded promising results, efficacious and reliable alternative approaches are yet to be developed. In this review article, we will describe Campylobacter-associated disease spectrums and current treatment options, discuss the state of antibiotic resistance and alternative therapies, and provide an evaluation of various approaches that are being developed to control Campylobacter infections in animal reservoirs and the human host.

Tracking Antimicrobial Resistance Determinants in Diarrheal Pathogens: A Cross-Institutional Pilot Study

Infectious diarrhea affects over four billion individuals annually and causes over a million deaths each year. Though not typically prescribed for treatment of uncomplicated diarrheal disease, antimicrobials serve as a critical part of the armamentarium used to treat severe or persistent cases. Due to widespread over- and misuse of antimicrobials, there has been an alarming increase in global resistance, for which a standardized methodology for geographic surveillance would be highly beneficial. To demonstrate that a standardized methodology could be used to provide molecular surveillance of antimicrobial resistance (AMR) genes, we initiated a pilot study to test 130 diarrheal pathogens (Campylobacter spp., Escherichia coli, Salmonella, and Shigella spp.) from the USA, Peru, Egypt, Cambodia, and Kenya for the presence/absence of over 200 AMR determinants. We detected a total of 55 different determinants conferring resistance to ten different categories of antimicrobials: genes detected in ≥ 25 samples included bla_TEM, tet(A), tet(B), mac(A), mac(B), aadA1/A2, strA, strB, sul1, sul2, qacEΔ1, cmr, and dfrA1. The number of determinants per strain ranged from none (several Campylobacter spp. strains) to sixteen, with isolates from Egypt harboring a wider variety and greater number of genes per isolate than other sites. Two samples harbored carbapenemase genes, bla_OXA-48 or bla_NDM. Genes conferring resistance to azithromycin (ere(A), mph(A)/mph(K), erm(B)), a first-line therapeutic for severe diarrhea, were detected in over 10% of all Enterobacteriaceae tested: these included >25% of the Enterobacteriaceae from Egypt and Kenya. Forty-six percent of the Egyptian Enterobacteriaceae harbored genes encoding CTX-M-1 or CTX-M-9 families of extended-spectrum β-lactamases. Overall, the data provide cross-comparable resistome information to establish regional trends in support of international surveillance activities and potentially guide geospatially informed medical care.

U-Omp19 from Brucella abortus increases dmLT immunogenicity and improves protection against Escherichia coli heat-labile toxin (LT) oral challenge

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Oral co-administration of dmLT with U-Omp19 increases dmLT immunogenicity.

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U-Omp19 oral co-delivery with dmLT induces anti-LT antibody responses.

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U-Omp19 co-administered with dmLT protects against oral challenge with LT.

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U-Omp19 can allow antigen dose sparing by oral route.

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U-Omp19 can be used as adjuvant in an oral vaccine formulation against ETEC.

Acute diarrhea disease caused by bacterial infections is a major global health problem. Enterotoxigenic Escherichia coli (ETEC) is one of the top causes of diarrhea-associated morbidity and mortality in young children and travelers to low-income countries. There are currently no licensed vaccines for ETEC. Induction of immunity at the site of entry of the bacteria is key to prevent infection. Current approaches to ETEC vaccines include a less toxic mutant form of E. coli heat-labile toxin (double-mutant heat-labile enterotoxin -dmLT-) with both antigenic and immunostimulatory properties. U-Omp19 is a protease inhibitor from Brucella spp. with immunostimulatory properties that has been used as oral adjuvant. In this work, we use U-Omp19 as adjuvant in an oral vaccine formulation against ETEC containing dmLT in outbred and inbred mice. To evaluate antigen dose sparing by U-Omp19 three different immunization protocols with three different doses of dmLT were evaluated. We demonstrated that U-Omp19 co-delivery increases anti-LT IgA in feces using a mid-dose of dmLT following a prime-boost protocol (after one or two boosts). Oral immunization with U-Omp19 induced protection against LT challenge when co-formulated with dmLT in CD-1 and BALB/c mice. Indeed, there was a significant increase in anti-LT IgG and IgA avidity after a single oral administration of dmLT plus U-Omp19 in comparison with dmLT delivered alone. Interestingly, sera from dmLT plus U-Omp19 vaccinated mice significantly neutralize LT effect on intestine inflammation in vivo compared with sera from the group immunized with dmLT alone. These results demonstrate the adjuvant capacity of U-Omp19 to increase dmLT immunogenicity by the oral route and support its use in an oral subunit vaccine formulation against ETEC.

Genome-wide screens reveal Escherichia coli genes required for growth of T1-like phage LL5 and V5-like phage LL12

The host factor requirements of phages and mechanisms of mutational phage insensitivity must be characterized for rational design of phage cocktails. To characterize host dependencies of two novel Escherichia coli phages, the T1-like siphophage LL5 and the V5-like myophage LL12, forward genetic screens were conducted against the Keio collection, a library of single non-essential gene deletions in E. coli str. BW25113. These screens and subsequent experiments identified genes required by phages LL5 and LL12. E. coli mutants deficient in heptose II and the phosphoryl substituent of heptose I of the inner core lipopolysaccharide (LPS) were unable to propagate phage LL5, as were mutants deficient in the outer membrane protein TolC. Mutants lacking glucose I of the LPS outer core failed to propagate LL12. Two additional genes encoding cytoplasmic chaperones, PpiB and SecB, were found to be required for efficient propagation of phage LL5, but not LL12. This screening approach may be useful for identifying host factors dependencies of phages, which would provide valuable information for their potential use as therapeutics and for phage engineering.

The Role of the Salmonella spvB IncF Plasmid and Its Resident Entry Exclusion Gene traS on Plasmid Exclusion

Salmonella enterica cause significant illnesses worldwide. There has been a marked increase in resistance to fluoroquinolones and β-lactams/cephalosporins, antibiotics commonly used to treat salmonellosis. However, S. enterica serovars vary in their resistance to these and other antibiotics. The systemic virulence of some Salmonella serovars is due to a low copy number, IncF plasmid (65-100 kb) that contains the ADP-ribosylating toxin, SpvB. This virulence plasmid is present in only nine Salmonella serovars. It is possible that the spvB-virulence plasmid excludes other plasmids and may explain why antibiotic resistance is slow to develop in certain Salmonella serovars such as S. Enteritidis. The distribution of plasmid entry exclusion genes traS/traT and traY/excA are variable in Salmonella IncF and IncI plasmids, respectively and may account for differences in emergent antimicrobial resistance for some Salmonella serovars. The goal of this study is to determine the contribution of the Salmonella spvB-virulence plasmid in F-plasmid exclusion. From conjugation experiments, S. Typhimurium exhibited lower conjugation frequency with incFI and incFII plasmids when the spvB-virulence plasmid is present. Furthermore, introduction of cloned incFI traS into a "plasmidless" S. Typhimurium LT2 strain and Escherichia coli DH5α excluded incFI plasmid. However, deletion of the virulence plasmid traS did not affect plasmid exclusion significantly compared to a spvB control deletion. In addition, differences in F plasmid conjugation in natural Salmonella isolates did not correlate with IncF or SpvB-virulence plasmid genotype. There appear to be other plasmid or chromosomal genes at play in plasmid exclusion that may be responsible for the slow development of antibiotic resistance in certain serovars.

Antimicrobial Resistance in the Asia Pacific region: a meeting report

The Asia Pacific region, home to two-thirds of the world's population and ten of the least developed countries, is considered a regional hot-spot for the emergence and spread of antimicrobial resistance (AMR). Despite this, there is a dearth of high-quality regional data on the extent of AMR. Recognising the urgency to close this gap, Singapore organised a meeting to discuss the problems in the region and frame a call for action. Representatives from across the region and beyond attended the meeting on the "Antimicrobial Resistance in the Asia Pacific & its impact on Singapore" held in November 2018. This meeting report is a summary of the discussions on the challenges and progress in surveillance, drivers and levers of AMR emergence, and the promising innovations and technologies that could be used to combat the increasing threat of AMR in the region. Enhanced surveillance and research to provide improved evidence-based strategies and policies are needed. The major themes that emerged for an action plan are working towards a tailored solution for the region by harnessing the One Health approach, enhancing inter-country collaborations, and collaboratively leverage upon new emerging technologies. A regionally coordinated effort that is target-driven, sustainable and builds on a framework facilitating communication and governance will strengthen the fight against AMR in the Asia Pacific region.

Travelers' Diarrhea in Thailand: A Quantitative Analysis Using TaqMan® Array Card

Background

Travelers' diarrhea (TD) is a common illness experienced by travelers from developed countries who visit developing countries. Recent questionnaire-based surveillance studies showed that approximately 6%-16% of travelers experienced TD while visiting Thailand; however, a majority of TD information was limited mainly to US military populations.

Methods

A TD surveillance study was conducted at Bumrungrad International Hospital in 2012-2014 in Bangkok, Thailand. Enteropathogens were identified using conventional methods and the TaqMan® array card (TAC), which uses real-time polymerase chain reaction for the simultaneous detection of multiple pathogens. Analyses to determine pathogen-disease and symptoms association were performed to elucidate the clinical relevance of each enteropathogen.

Results

TAC identified more pathogens per sample than conventional methods. Campylobacter spp. were the most prevalent, followed by the diarrheagenic Escherichia coli and norovirus GII. These agents had significant pathogen-disease associations as well as high attributable fractions among diarrheal cases. A wide range of pathogen loads for Campylobacter spp. was associated with TD, while heat-labile toxin enterotoxigenic Escherichia coli was associated with an increased pathogen load. Most cases were associated with inflammatory diarrhea, while Campylobacter spp. and Shigella spp. were associated with dysentery.

Conclusions

A pan-molecular diagnostic method such as TAC produces quantifiable and comparable results of all tested pathogens, thereby reducing the variability associated with multiple conventional methods. This allows better determination of the clinical relevance of each diarrhea etiologic agent, as well as their geographical relevance in Thailand.

Complete Genome Sequence of Enterotoxigenic Escherichia coli Myophage LL12

This work describes the complete genome sequence of the virulent myophage LL12. The 136-kb LL12 genome is related to coliphage V5 and is a component in the prebiotic PreforPro. LL12 was isolated against enterotoxigenicEscherichia coli, which causes traveler’s diarrhea.

Winning the War against Multi-Drug Resistant Diarrhoeagenic Bacteria

Drug-resistant-diarrhoeagenic bacteria are currently emerging healthcare challenge. This study investigated the effects of Vernonia amygdalina, Garcinia kola, tetracycline and metronidazole combinations on such bacteria. Agar well diffusion method was employed to determine the inhibitory effects of the herbal extracts on diarrhoeagenic bacteria while Time-Kill Assay was used to determine bactericidal effects of the extracts against test isolates. Interactions between plant extracts and antibiotics were investigated using Checkerboard assay. Minimum inhibitory concentrations of the extracts against the bacterial isolates ranged between 3.125–50 mg/mL, while those of tetracycline and metronidazole ranged from 30–50 μg/mL. Synergism was observed against B. cereus and S. aureus for metronidazole + aqueous G. kola at all ratios. Generally, the combinations aqueous G. kola + ethanolic G. kola and aqueous G. kola + ethanolic V. amygdalina showed more pronounced synergism against the Staphylococcus aureus than B. cereus isolates with the fractional inhibition concentration (FIC) indices ranging from 0.32–0.95. Synergism of tetracycline + crude extracts and metronidazole combinations were more pronounced on the test isolates and especially on the Gram-negative organisms with FIC indices ranging from 0.41–0.91. Conclusion: The herbal extracts combinations and extracts–antibiotics combinations are synergistic on diarrhoeagenic bacteria at defined combination ratios.

Complete Genome Sequence of Enterotoxigenic Escherichia coli Siphophage LL5

Here, we describe the complete genome sequence of siphophage LL5. LL5 is a T1-like phage isolated against enterotoxigenic Escherichia coli , which causes traveler’s diarrhea. LL5 is included as a component phage in the commercial prebiotic product PreforPro.

Enterotoxigenic Escherichia coli Infections

PURPOSE OF REVIEW

Review recent developments pertaining to the epidemiology, molecular pathogenesis, and sequelae of enterotoxigenic Escherichia coli (ETEC) infections in addition to discussion of challenges for vaccinology.

RECENT FINDINGS

ETEC are a major cause of diarrheal illness in resource poor areas of the world where they contribute to unacceptable morbidity and continued mortality particularly among young children; yet, precise epidemiologic estimates of their contribution to death and chronic disease have been difficult to obtain. Although most pathogenesis studies, and consequently vaccine development have focused intensively on canonical antigens, more recently identified molecules unique to the ETEC pathovar may inform our understanding of ETEC virulence, and the approach to broadly protective vaccines. ETEC undeniably continue to have a substantial impact on global health; however, further studies are needed to clarify the true impact of these infections, particularly in regions where access to care may be limited. Likewise, our present understanding of the relationship of ETEC infection to non-diarrheal sequelae is presently limited, and additional effort will be required to achieve a mechanistic understanding of these diseases and to fulfill Koch's postulates on a molecular level. Precise elucidation of the role played by novel virulence factors, the global burden of acute illness, and the contribution of these pathogens and/or their toxins to non-diarrheal morbidity remain important imperatives.

Cross-Protective Shigella Whole-Cell Vaccine With a Truncated O-Polysaccharide Chain

Shigella is a highly prevalent bacterium causing acute diarrhea and dysentery in developing countries. Shigella infections are treated with antibiotics but Shigellae are increasingly resistant to these drugs. Vaccination can be a countermeasure against emerging antibiotic-resistant shigellosis. Because of the structural variability in Shigellae O-antigen polysaccharides (Oag), cross-protective Shigella vaccines cannot be derived from single serotype-specific Oag. We created an attenuated Shigella flexneri 2a strain with one rather than multiple Oag units by disrupting the Oag polymerase gene (Δwzy), which broadened protective immunogenicity by exposing conserved surface proteins. Inactivated Δwzy mutant cells combined with Escherichia coli double mutant LT(R192G/L211A) as adjuvant, induced potent antibody responses to outer membrane protein PSSP-1, and type III secretion system proteins IpaB and IpaC. Intranasal immunization with the vaccine preparation elicited cross-protective immunity against S. flexneri 2a, S. flexneri 3a, S. flexneri 6, and Shigella sonnei in a mouse pneumonia model. Thus, S. flexneri 2a Δwzy represents a promising candidate strain for a universal Shigella vaccine.

Morbidity and mortality due to shigella and enterotoxigenic Escherichia coli diarrhoea: the Global Burden of Disease Study 1990-2016

Background

Shigella and enterotoxigenic Escherichia coli (ETEC) are bacterial pathogens that are frequently associated with diarrhoeal disease, and are a significant cause of mortality and morbidity worldwide. The Global Burden of Diseases, Injuries, and Risk Factors study 2016 (GBD 2016) is a systematic, scientific effort to quantify the morbidity and mortality due to over 300 causes of death and disability. We aimed to analyse the global burden of shigella and ETEC diarrhoea according to age, sex, geography, and year from 1990 to 2016.

Methods

We modelled shigella and ETEC-related mortality using a Bayesian hierarchical modelling platform that evaluates a wide range of covariates and model types on the basis of vital registration and verbal autopsy data. We used a compartmental meta-regression tool to model the incidence of shigella and ETEC, which enforces an association between incidence, prevalence, and remission on the basis of scientific literature, population representative surveys, and health-care data. We calculated 95% uncertainty intervals (UIs) for the point estimates.

Findings

Shigella was the second leading cause of diarrhoeal mortality in 2016 among all ages, accounting for 212 438 deaths (95% UI 136 979–326 913) and about 13·2% (9·2–17·4) of all diarrhoea deaths. Shigella was responsible for 63 713 deaths (41 191–93 611) among children younger than 5 years and was frequently associated with diarrhoea across all adult age groups, increasing in elderly people, with broad geographical distribution. ETEC was the eighth leading cause of diarrhoea mortality in 2016 among all age groups, accounting for 51 186 deaths (26 757–83 064) and about 3·2% (1·8–4·7) of diarrhoea deaths. ETEC was responsible for about 4·2% (2·2–6·8) of diarrhoea deaths in children younger than 5 years.

Interpretation

The health burden of bacterial diarrhoeal pathogens is difficult to estimate. Despite existing prevention and treatment options, they remain a major cause of morbidity and mortality globally. Additional emphasis by public health officials is needed on a reduction in disease due to shigella and ETEC to reduce disease burden.

Funding

Bill & Melinda Gates Foundation.

Extended-spectrum β-lactamase prevalence and virulence factor characterization of enterotoxigenic Escherichia coli responsible for acute diarrhea in Nepal from 2001 to 2016

Background

Multidrug-resistant (MDR) Gram-negative bacterial species are an increasingly dangerous public health threat, and are now endemic in many areas of South Asia. However, there are a lack of comprehensive data from many countries in this region determining historic and current MDR prevalence. Enterotoxigenic Escherichia coli (ETEC) is a leading cause of both acute infant diarrhea and traveler’s diarrhea in Nepal. The MDR prevalence and associated resistance mechanisms of ETEC isolates responsible for enteric infections in Nepal are largely unknown.

Methods

A total of 265 ETEC isolates were obtained from acute diarrheal samples (263/265) or patient control samples (2/265) at traveler’s clinics or regional hospitals in Nepal from 2001 to 2016. Isolates were screened for antibiotic resistance, to include extended spectrum beta-lactamase (ESBL) production, via the Microscan Automated Microbiology System. ETEC virulence factors, specifically enterotoxins and colonization factors (CFs), were detected using multiplex PCR, and prevalence in the total isolate population was compared to ESBL-positive isolates. ESBL-positive isolates were assessed using multiplex PCR for genetic markers potentially responsible for observed resistance.

Results

A total of 118/265 (44.5%) ETEC isolates demonstrated resistance to ≥2 antibiotics. ESBL-positive phenotypes were detected in 40/265 isolates, with isolates from 2008, 2013, 2014, and 2016 demonstrating ESBL prevalence rates of 1.5, 34.5, 31.2, and 35.0% respectively. No difference was observed in overall enterotoxin characterization between the total ETEC and ESBL-positive populations. The CFs CS2 (13.6%), CS3 (25.3%), CS6 (30.2%), and CS21 (62.6%) were the most prevalent in the total ETEC population. The ESBL-positive ETEC isolates exhibited a higher association trend with the CFs CS2 (37.5%), CS3 (35%), CS6 (42.5%), and CS21 (67.5%). The primary ESBL gene identified was bla_CTX-M-15 (80%), followed by bla_SHV-12 (20%) and bla_CTX-M-14 (2.5%). The beta-lactamase genes bla_TEM-1 (40%) and bla_CMY-2 (2.5%) were also identified. It was determined that 42.5% of the ESBL-positive isolates carried multiple resistance genes.

Conclusion

Over 30% of ETEC isolates collected post-2013 and evaluated in this study demonstrated ESBL resistance. Persistent surveillance and characterization of enteric ETEC isolates are vital for tracking the community presence of MDR bacterial species in order to recommend effective treatment strategies and help mitigate the spread of resistant pathogens.

In vitro activity of fosfomycin against Campylobacter isolates from poultry and wild birds

Fosfomycin is a broad-spectrum antibiotic with the activity against both Gram-positive and Gram-negative pathogens by inhibiting the bacterial cell wall synthesis. Given the potential therapeutic efficacy of fosfomycin against Campylobacter spp., the aim of the present study was to determine the in vitro fosfomycin susceptibility of Campylobacter isolates from avian sources including poultry and wild birds. A total of eight (1.8%) strains of Campylobacter including five C. jejuni strains isolated from ducks and three C. coli strains isolated from chickens and duck showed resistance to fosfomycin, with MICs ranging from 64 to ≥ 256 μg/mL. The extent of fosfomycin resistance was 0%, 0.9% and 3.9% in wild birds, chicken and ducks respectively. The MIC50, MIC90, and MIC100 values were 8, 32, and 32 μg/mL respectively in wild bird, 32, 32, and 64 μg/mL respectively in chicken, and 32, 32, and ≥ 256 μg/mL respectively in ducks. All eight fosfomycin-resistant Campylobacter strains were multidrug resistant; six were also resistant to fluoroquinolones, ampicillin, and tetracycline, and two were also resistant to fluoroquinolones, ampicillin, tetracycline, and macrolides. However, the fosfomycin resistance gene fosXCC was not detected in the eight fosfomycin-resistant strains. Because food animals can harbor fosfomycin-resistant Campylobacter and transmit them to humans, greater efforts are needed to monitor the prevalence of fosfomycin resistance in Campylobacter strains isolated from such animals.

Antimicrobial resistance profiles of Shigella dysenteriae isolated from travellers returning to the UK, 2004-2017

PURPOSE

Antimicrobial resistance (AMR) profiles of 754 strains of Shigella dysenteriae isolated between 2004 and 2017 from UK travellers reporting symptoms of gastrointestinal (GI) disease were reviewed to look for evidence of emerging AMR associated with travellers' diarrhoea.

METHODOLOGY

A travel history was provided for 72.7 % (548/754) of cases, of which 90.9 % (498/548) reported travel outside the UK within 7 days of onset of symptoms, and 9.1 % (50/498) reported no travel in that time frame. During the course of this study, whole genome sequencing (WGS) was implemented for GI disease surveillance, and we compared phenotypic AMR profiles with those derived from WGS data (n=133).Results/Key findings. The phenotypic and genotypic AMR results correlated well, with 90.1 % (121/133) isolates having concordant results to 10 classes of antimicrobials. Resistance to the first-line drugs commonly used in the treatment of shigellosis was observed throughout the study (ampicillin, 54.1%; chloramphenicol, 33.7 %; sulphonamides, 76.0 %; trimethoprim, 80.0%). Between 2004 and 2017, resistance to all classes of antimicrobials (except the phenicols) increased. The proportion of isolates exhibiting reduced susceptibility to ciprofloxacin increased from 3.8 % in 2004 to 75.7 % in 2017, and this was significantly associated with cases reporting travel to Asia compared to Africa (P<0.001). Of the 201 sequenced isolates, 3.0 % (20/201) had either blaCTX-M-15 or blaCMY-4.

CONCLUSIONS

Increasing MDR, along with resistance to the fluroquinolones and the third generation cephalosporins, in Shigella dysenteriae causing travellers' diarrhoea provides further evidence for the need to regulatethe use of antimicrobial agents and continuous monitoring of emerging AMR.

Development, Interlaboratory Evaluations, and Application of a Simple, High-Throughput Shigella Serum Bactericidal Assay

Shigella is an important cause of diarrhea worldwide, and efforts are ongoing to produce a safe and effective Shigella vaccine. Although a clear immune correlate of protection has not been established, antibodies with bactericidal capacity may provide one means of protecting against shigellosis. Thus, it is important to measure the functional capacity of antibodies, as opposed to only binding activity. This article describes a simple, robust, and high-throughput serum bactericidal assay capable of measuring Shigella-specific functional antibodies in vitro. We show for the first time that this assay was successfully performed by multiple laboratories and generated highly comparable results, particularly when SBA titers were normalized using a reference standard. The serum bactericidal assay, along with a reference serum, should greatly facilitate Shigella vaccine development.

Shigella is an important cause of diarrhea worldwide, with serotypes Shigella flexneri 2a, S. flexneri 3a, and Shigella sonnei demonstrating epidemiological prevalence. Many development efforts are focused on Shigella lipopolysaccharide (LPS)-based vaccines, as O antigen-specific conjugate vaccines are immunogenic and efficacious. Immunization with Shigella vaccines containing LPS can elicit antibodies capable of killing Shigella in a serotype-specific manner. Thus, to facilitate Shigella vaccine development, we have developed a serum bactericidal assay (SBA) specific for three Shigella serotypes that measures killing of target bacteria at multiple serum dilutions and in the presence of exogenous complement. The SBA has a high analytical throughput and uses simple technologies and readily available reagents. The SBA was characterized with human sera with bactericidal antibodies against S. flexneri 2a, S. flexneri 3a, and S. sonnei. Purified LPS of a homologous serotype, but not a heterologous serotype, inhibited bacterial killing. Assessment of precision found median intra-assay precision to be 13.3% and median interassay precision to be 19 to 30% for the three serotypes. The SBA is linear, with slight deviations for samples with low (~40) killing indices. The SBA was sensitive enough to allow about 100-fold predilution of serum samples. Repeat assays yielded results with less than 2-fold deviations, indicating the robustness of the assay. Assay results from four different laboratories were highly comparable when normalized with a reference serum. The Shigella SBA, combined with a reference serum, should facilitate the development of Shigella vaccines across the field.

IMPORTANCEShigella is an important cause of diarrhea worldwide, and efforts are ongoing to produce a safe and effective Shigella vaccine. Although a clear immune correlate of protection has not been established, antibodies with bactericidal capacity may provide one means of protecting against shigellosis. Thus, it is important to measure the functional capacity of antibodies, as opposed to only binding activity. This article describes a simple, robust, and high-throughput serum bactericidal assay capable of measuring Shigella-specific functional antibodies in vitro. We show for the first time that this assay was successfully performed by multiple laboratories and generated highly comparable results, particularly when SBA titers were normalized using a reference standard. The serum bactericidal assay, along with a reference serum, should greatly facilitate Shigella vaccine development.

Antibiotic resistance in travellers' diarrhoeal disease, an external perspective

BACKGROUND

There are many recommendations on the use of antibiotics for prophylaxis and treatment of travellers' diarrhoea (TD). As pharmacists with a special interest in antimicrobial stewardship, we examine and offer our perspective on advice that is recommended to travellers in terms of prevention, treatment and management of TD with a focus on antibiotic use and resistance.

METHODS

Publications on TD were identified through PubMed, Google Scholar and Cochrane Library databases searches using search terms 'travellers diarrhoea', 'travellers diarrhoea', 'travellers' diarrhoea' 'guidelines', 'expert opinion', 'expert reviews', 'South Asia' and 'South East Asia' (S and SE Asia), 'antibiotics', 'resistance genes', 'travel advice', 'pharmacists', 'guidelines', 'prevention' and 'treatment'. References of articles were also screened for additional relevant studies.

RESULTS

Whilst most guidelines and expert reviews were in agreement with the restricted use of antibiotics unless there was a clinical need, the literature review identified gaps in research into behaviours of travellers regarding non-compliance with the pre-travel advice provided and the need for in depth training and education for all healthcare professionals in providing 'tailored' advice for travellers going to high-risk destinations.

CONCLUSIONS

Travellers should be made aware of the problems of antimicrobial resistance in their destination and home countries and offered alternative forms of prophylaxis for TD. Strategies for prevention of TD, other than the use of antibiotics, also need to be emphasized. All healthcare professionals involved in giving advice about TD should be familiar with the epidemiology of the condition as this will inform responsible behaviours, risk assessment and management strategies in different geographical areas.

Rifamycin SV-MMX® for treatment of travellers' diarrhea: equally effective as ciprofloxacin and not associated with the acquisition of multi-drug resistant bacteria

BACKGROUND

The novel oral antibiotic formulation Rifamycin SV-MMX®, with a targeted delivery to the distal small bowel and colon, was superior to placebo in treating travellers' diarrhea (TD) in a previous study. Thus, a study was designed to compare this poorly absorbed antibiotic with the systemic agent ciprofloxacin.

METHODS

In a randomized double-blind phase 3 study (ERASE), the efficacy and safety of Rifamycin SV-MMX® 400 mg twice daily (RIF-MMX) was compared with ciprofloxacin 500 mg twice daily in the oral treatment of TD. Overall, 835 international visitors to India, Guatemala or Ecuador with acute TD were randomized to receive a 3-day treatment with RIF-MMX (n = 420) or ciprofloxacin (n = 415). Primary endpoint was time to last unformed stool (TLUS), after which clinical cure was declared. Stools samples for microbiological evaluation were collected at the baseline visit and the end of treatment visit.

RESULTS

Median TLUS in the RIF-MMX group was 42.8 h versus 36.8 h in the ciprofloxacin group indicating non-inferiority of RIF-MMX to ciprofloxacin (P = 0.0035). Secondary efficacy endpoint results including clinical cure rate, treatment failure rate, requirement of rescue therapy as well as microbiological eradication rate confirmed those of the primary analysis indicating equal efficacy for both compounds. While patients receiving ciprofloxacin showed a significant increase of Extended Spectrum Beta Lactamase Producing-Escherichia coli (ESBL-E. Coli) colonization rates after 3-days treatment (6.9%), rates did not increase in patients receiving RIF-MMX (-0.3%). Both drugs were well-tolerated and safe.

CONCLUSION

The novel multi-matrix formulation of the broad-spectrum, poorly absorbed antibiotic Rifamycin SV was found non-inferior to the systemic antibiotic ciprofloxacin in the oral treatment of non-dysenteric TD with the advantage of a lower risk of ESBL-E. Coli acquisition.