Cholera

Functional role of rpoN in regulating the virulence of non-O1/O139 Vibrio cholerae

Non-O1/O139 Vibrio cholerae is widely distributed in brackish and estuarine ecosystems, which can infect many aquatic animals. RpoN, an alternative sigma factor, plays a critical role in regulating cell functions such as motility, quorum sensing, and virulence. However, the function of rpoN in non-O1/O139 V. cholerae has rarely been reported. In the present study, we constructed the deletion mutant ΔrpoN of non-O1/O139 V. cholerae GXFL1-4 using recombination technology and investigated the function of rpoN through transcriptomic and phenotypic analyses. RNA-seq results showed that many major virulence-related genes were down-regulated in the ΔrpoN mutant, including the type VI secretion system (tssJ, tssA, tagO, tssG), type IV pilus assembly proteins (pilM, pilB), biofilm formation genes (vpsC, cheC), and hemolysin-related genes (hlyD, hlyD-PA). Additionally, phenotypic assays showed that the growth and motility of the ΔrpoN had no apparent change. The deletion of rpoN in non-O1/O139 V. cholerae led to decreased biofilm formation and reduced hemolytic activity. Furthermore, artificial infection tests showed that the virulence of the ΔrpoN mutant toward Macrobrachium rosenbergii was decreased. Our study provides essential insights into the regulatory function of rpoN, revealing that rpoN is a key determinant of virulence regulation in non-O1/O139 V. cholerae.

Regulatory mechanisms of two-component systems in Vibrio cholerae: Enhancing pathogenicity and environmental adaptation

Cholera, which is caused by the bacterium Vibrio cholerae, is a highly dangerous disease characterized by severe symptoms such as watery diarrhea, dehydration, and even death. V. cholerae can both colonize the host intestine and survive in environmental reservoirs. Two-component systems (TCSs) are essential regulatory mechanisms that allow bacteria to adapt to changing environments. This review focuses on the regulatory mechanisms of TCS-mediated gene expression in V. cholerae. We first summarize the composition and classification of TCSs in V. cholerae N16961. We then discuss the roles of TCSs in facilitating adaptation to diverse environmental stimuli and increasing pathogenicity. Furthermore, we analyze the distribution of TCSs in pandemic and nonpandemic-V. cholerae strains, demonstrating their indispensable role in promoting virulence and facilitating the widespread dissemination of pandemic strains. Elucidation of these mechanisms is crucial for devising new strategies to combat cholera and prevent future outbreaks, ultimately contributing to improved public health outcomes.

Assessment of knowledge, attitudes and practices regarding cholera among people living in a cholera-endemic health zone in the Democratic Republic of the Congo

OBJECTIVES

To assess cholera-related knowledge, attitudes and practices (KAP) and identify associated factors in a cholera endemic health zone in the Democratic Republic of the Congo (DRC).

DESIGN

A community-based cross-sectional study.

SETTING

The study was conducted in Kalemie health zone, which is located in the Tanganyika province in eastern DRC.

PARTICIPANTS

A total of 455 participants were enrolled in this study using a three-stage random sampling procedure.

MAIN OUTCOME MEASURES

Sociodemographic characteristics, cholera and water, sanitation and hygiene (WASH)-related KAP, and their associated factors.

RESULTS

The study revealed that the population demonstrated a good knowledge (64%), a positive attitude (73.6%) and good WASH practices (73.8%) regarding cholera. The identification of cholera symptoms, modes of transmission and means of prevention ranged from 79.6% to 94.3%, 38.2% to 41.5% and 32.5% to 56.3%, respectively. It was also noted a high prevalence of tap water use (93.4%) and limited access to water treatment (43.1% to 57.1%), as well as a significant proportion of latrine access (70.8%) with the presence of open defecation (16.3%). In multivariable logistic regression, poor knowledge about cholera was associated with being aged 18 years or younger, having limited education and practising poor WASH habits. No significant factors influenced participants' attitudes. Poor WASH practices were associated with being from households with daily expenditures of less than 1 USD and 5 USD, as well as having poor knowledge about cholera. In addition, believers from Catholic and Muslim backgrounds were less likely to have poor WASH practices.

CONCLUSIONS

Our findings indicate that health education initiatives targeting younger demographics should be intensified to enhance awareness of cholera prevention and household water treatment. Furthermore, there is a need for targeted interventions to provide public standpipes and community boreholes, as well as to improve the coverage of covered pit latrines, especially for poorer households.

Non-toxigenic Vibrio cholerae - just another cause of vibriosis or a potential new pandemic?

Although nontoxigenic Vibrio cholerae usually stands in the shadow of the two serogroups (O1 and O139) that cause pandemic cholera, its role in human pathology is increasingly recognized and described in the literature. The habitat of these pathogens is brackish seawater or even freshwater, and the infections caused by them include contact with these waters or consumption of seafood originating in this habitat, which is constantly expanding because of global warming. This habitat extension is a typical example of climate change's impact on infectious diseases. Although nontoxigenic Vibrio cholerae strains are rarely capable of producing the classical cholera toxin, they possess many other virulence factors, can secrete various other toxins, and thus produce illnesses that are sometimes even severe or life-threatening, more frequently in immunocompromised patients. Vibriosis may manifest as gastrointestinal illnesses, wounds, skin or subcutaneous tissue infections, or septicemia. To establish the correct etiological diagnosis for these infections, a high index of suspicion must be maintained, as the diagnostic techniques require targeted investigations and specific collection and transportation of the samples. Empiric treatment recommendations are available, but owing to the increasing resistance of this pathogen, susceptibility testing is needed for every diagnosed case. We intend to raise awareness regarding these infections, as they tend to be more frequent than they were in the past and to appear in areas where they had not been recognized before.

Evaluation of oral cholera vaccine (Euvichol-Plus) effectiveness against Vibrio cholerae in Bangladesh: an interim analysis

INTRODUCTION

Millions of Euvichol-Plus doses have been deployed from the global oral cholera vaccine stockpile in over 20 cholera-affected countries. However, information on Euvichol-Plus's effectiveness is limited. Using this vaccine in a cholera epidemic in Dhaka, Bangladesh, provided the opportunity to evaluate the vaccine effectiveness (VE) using a test-negative design.

METHODS

A two-dose regimen of Euvichol-Plus was administered to individuals aged >1 year in a population of ca. 900 000 in two campaign rounds between June and August 2022, with prospective registration of all persons who received at least one dose. We conducted systematic surveillance in two key facilities, enrolling patients with acute watery diarrhoea who were eligible for vaccination from the campaign's start and who presented for care between 21 August 2022 and 20 August 2023. Faecal culture-positive cholera cases were matched to up to four faecal culture-negative controls by age, presentation date and facility. Vaccination status was documented without knowledge of culture results. Conditional logistic regression models estimated the OR for the vaccination-cholera association, and the VE of the two-dose regimen was calculated as [(1-OR) × 100].

RESULTS

The analysis included 226 cases and 552 matched controls. The adjusted VE of two doses of the Euvichol-Plus vaccine against medically attended cholera was 66% (99.5% CI: 30 to 83) for all recipients. Limited protection (12%; 95% CI: -95 to 60) was observed for children aged 1-4 years; whereas, protection was 79% (95% CI: 60 to 89) for those aged ≥5 years. VE against cholera with moderate to severe dehydration was 69% (95% CI: 44 to 83) overall but 6% (95% CI: -206 to 71) for children aged 1-4 years.

CONCLUSION

Euvichol-Plus provided significant protection against medically attended cholera of any severity as well as cholera with moderate to severe dehydration. However, significant levels of protection were only observed for those aged ≥5 years.

Vibrio cholerae virulence and its suppression through the quorum-sensing system

Vibrio cholerae is a cholera-causing pathogen known to instigate severe contagious diarrhea that affects millions globally. Survival of vibrios depend on a combination of multicellular responses and adapt to changes that prevail in the environment. This process is achieved through a strong communication at the cellular level, the process has been recognized as quorum sensing (QS). The severity of infection is highly dependent on the QS of vibrios in the gut milieu. The quorum may exist in a low/high cell density (LCD/HCD) state to exert a positive or negative response to control the regulatory pathogenic networks. The impact of this regulation reflects on the transition of pathogenic V. cholerae from the environment to infect humans and cause outbreaks or epidemics of cholera. In this context, the review portrays various regulatory processes and associated virulent pathways, which maneuver and control LCD and HCD states for their survival in the host. Although several treatment options are existing, promotion of therapeutics by exploiting the virulence network may potentiate ineffective antibiotics to manage cholera. In addition, this approach is also useful in resource-limited settings, where the accessibility to antibiotics or conventional therapeutic options is limited.

Cholera outbreak in Mayotte (France): A retrospective description of 16 patients treated for hypovolemia in the ICU

OBJECTIVES

To describe the presentation and therapeutic management of severe cholera in Mayotte (France).

PATIENTS AND METHODS

We carried out retrospective data collection. All patients treated in the intensive care unit (ICU) with a confirmed diagnosis of cholera by PCR were studied. Only patients treated for hypovolemia were included.

RESULTS

Out of the 215 confirmed cases of cholera in Mayotte on July 12, 2024, 25 required treatment in the ICU (11.6 %). Among these cases, 16 were treated for hypovolemia (7.4 %), while five patients died of cholera before they could be admitted to hospital (lethality rate 2.3 %). No patient died in hospital. Median patient age was 17 years (4-30) with a sex ratio of 1. Severe diarrhea was the rule with a median of one diarrheal stool every two hours. Clinical severity was characterized by sunken eyes and Glasgow Coma Scale (GCS) < 14 (n = 16/16,100 %). Biological severity was determined by profound metabolic acidosis with venous pH < 7.20 (n = 16/16, 100 %). Intravenous fluid therapy was aggressive with a median of 280 mL/kg (230-300) Ringer's lactate solution during the first 48 h.

CONCLUSIONS

Cholera can be a life-threatening infection, with deaths occurring due to severe diarrhea and hypovolemia. From the onset of symptoms, which are sometimes fulminant, patients must be admitted to a care center as soon as possible. We will continue to collect data to create scores that will enable us to better recognize the most severe forms of the disease.

Spatio-temporal patterns of cholera outbreak in rural settings of Ethiopia, 2023

Objectives

The aim of this study was to assess the spatio-temporal pattern of cholera in rural settings of Ethiopia.

Methods

A spatiotemporal analysis of daily cholera cases in 59 Kebeles across 7 districts in the Gedeo zone from April 2 to November 18, 2023, obtained from the Gedeo Zone Health Department, was conducted. The global Moran's I statistic was used for spatial autocorrelation analysis, and the retrospective space-time scan statistic was used to analyze spatiotemporal clusters of cholera.

Results

Throughout the outbreak, 792 cholera cases were reported, corresponding to an annual incidence of 169.4 per 100,000 population. The spatial distribution showed strong autocorrelation, with a global Moran's I coefficient of 0.272 (P-value <0.001). Five statistically significant clusters were identified by space-time scan statistics using a discrete Poisson model. These identified clusters overlapped in time and had longer durations with a relatively high risk of cholera in the study areas.

Conclusion

The identification of high-risk clusters specific to rural settings forms the basis for rapid public health emergency response and resource allocation by prioritizing the significantly high-risk clusters to control and eventually eliminate cholera. There is room to improve the public health response to cholera outbreaks in the study settings.

Vibrio cholerae Gut Colonization of Zebrafish Larvae Induces a Dampened Sensorimotor Response

Background: Cholera is a diarrheal disease prevalent in populations without access to clean water. Cholera is caused by Vibrio cholerae, which colonizes the upper small intestine in humans once ingested. A growing number of studies suggest that the gut microbiome composition modulates animal behavior. Zebrafish are an established cholera model that can maintain a complex, mature gut microbiome during infection. Larval zebrafish, which have immature gut microbiomes, provide the advantage of high-throughput analyses for established behavioral models. Methods: We identified the effects of V. cholerae O1 El Tor C6706 colonization at 5 days post-fertilization (dpf) on larval zebrafish behavior by tracking startle responses at 10 dpf. We also characterized the larval gut microbiome using 16S rRNA sequencing. V. cholerae-infected or uninfected control groups were exposed to either an alternating light/dark stimuli or a single-tap stimulus, and average distance and velocity were tracked. Results: While there was no significant difference in the light/dark trial, we report a significant decrease in distance moved for C6706-colonized larvae during the single-tap trial. Conclusion: This suggests that early V. cholerae colonization of the larval gut microbiome has a dampening effect on sensorimotor function, supporting the idea of a link between the gut microbiome and behavior.

Genomic insights into the dynamic antibiotic resistance landscape of Vibrio cholerae during the Cholera outbreak 2022 in Odisha, India

This research delves into the evolving dynamics of antibiogram trends, the diversity of antibiotic resistance genes and antibiotic efficacy against Vibrio cholerae strains that triggered the cholera outbreak 2022 in Odisha, India. The study will provide valuable insights managing antimicrobial resistance during cholera outbreaks. Eighty V. cholerae strains isolated during the outbreak were analysed for genotypic variations in associated drug resistance genes using PCR assays. Antibiogram profiles and MIC gradient analysis were performed according CLSI guidelines to assess antibiotic effectiveness. Substitution of amino acid position in the QRDR Region was examined to understand the development of Fluoroquinolone resistance. Elevated resistances in V. cholerae strains were observed against doxycycline, azithromycin, ciprofloxacin, and chloramphenicol. The average MARI registered 0.63 value, exceeding the threshold value 0.2. PCR assays revealed higher prevalence of antibiotic resistance genes, and MIC values observed have surpassed the previously registered values during any cholera outbreaks in India. Novel mutations in the parC gene, specifically Tyr-88→Cys and Ser-85→Leu implicated Fluoroquinolone resistance in V. cholerae. This study urges moving beyond on antibiotic reliance to control cholera, emphasizing alternative strategies like OCV, rehydration therapy, probiotics and Water, Sanitation and Hygiene (WASH) interventions as effective tools to combat cholera outbreaks and mitigate antibiotic resistance.

The role of morphological adaptability in Vibrio cholerae's motility

Vibrio cholerae, the causative agent of cholera, displays remarkable adaptability to diverse environmental conditions through morphological changes that enhance its pathogenicity and influence the global epidemiology of the disease. This study examines the motility differences between filamentous and comma-shaped forms of the V. cholerae O1 strain under various viscosity conditions. Utilizing the El Tor strain, we induced filamentous transformation and conducted a comparative analysis with the canonical comma-shaped morphology. Our methodology involved assessing motility patterns, swimming speeds, rotation rates, kinematics, and reversal frequencies using dark-field microscopy and high-speed imaging techniques. The results show that filamentous V. cholerae cells retain enhanced motility in viscous environments, indicating an evolutionary adaptation for survival in varied habitats, particularly the human gastrointestinal tract. Filamentous forms exhibited increased reversal behavior at mucin interfaces, suggesting an advantage in penetrating the mucus layer. Furthermore, the presence of filamentous cells in bile-supplemented medium underscores their relevance in natural infection scenarios.

IMPORTANCE

This study highlights the enhanced motility of filamentous Vibrio cholerae in viscous environments, an adaptation that may provide a survival advantage in the human gastrointestinal tract. By demonstrating increased reversal behavior at mucin interfaces, filamentous V. cholerae cells exhibit a superior ability to penetrate the mucus layer, which is crucial for effective colonization and infection. Filamentous cells in bile-supplemented media further underscores their potential role in disease pathogenesis. These findings offer critical insights into the morphological flexibility of V. cholerae and its potential implications for infection dynamics, paving the way for more effective strategies in managing and preventing cholera outbreaks.

A fatal case of Vibrio cholerae-associated diarrhea and bacteremia in a 30-year-old carrier of beta-thalassemia

Bacterial infections leading to bacteremia and septicemic shock constitute an emerging public health concern globally, especially in areas where sanitation is poor and safe drinking water is scarce. Enteric pathogens such as Vibrio cholerae are responsible for many deaths caused by contaminated food and water in these areas. While cholera is the prominent clinical threat posed by V. cholerae, outcomes like bacteremia turning into sepsis and associated morbidity and mortality have been increasing globally in recent times. Here, we report an alarming case of fatal sepsis with a probable association of V. cholerae bacteremia in Bangladesh. In September 2023, a 30-year-old man with a pre-condition of beta-thalassemia presented to a tertiary care hospital with acute diarrhea, abdominal pain, nausea, and fever and died within 36 h of admission with acute cholecystitis, metabolic acidosis, acute kidney injury, pancytopenia, and refractory septic shock with multi-organ dysfunction syndrome. Blood culture detected V. cholerae, which was further characterized as hemolytic, carrying the hemolysin gene and genes for the virulence factor type-three secretion system. The isolate was confirmed as V. cholerae non-O1/O139 (NOVC), which differed in genetic properties from the few contemporary NOVC isolates associated with diarrheal cases in Bangladesh. To manage the diarrhea and septicemic condition, the patient was treated empirically with metronidazole and meropenem. However, antibiotic susceptibility testing showed the strain was susceptible to all the routinely prescribed drugs for V. cholerae infections. To the best of our knowledge, this investigation provides the first molecular description of a fatal case of V. cholerae-associated bacteremia in Bangladesh and underscores the need for comprehensive investigations on bacterial septicemia to prevent future casualties.

Three-dimensional structures of Vibrio cholerae typing podophage VP1 in two states

Lytic podophages (VP1-VP5) play crucial roles in subtyping Vibrio cholerae O1 biotype El Tor. However, until now no structures of these phages have been available, which hindered our understanding of the molecular mechanisms of infection and DNA release. Here, we determined the cryoelectron microscopy (cryo-EM) structures of mature and DNA-ejected VP1 structures at near-atomic and subnanometer resolutions, respectively. The VP1 head is composed of 415 copies of the major capsid protein gp7 and 11 turret-shaped spikes. The VP1 tail consists of an adapter, a nozzle, a slender ring, and a tail needle, and is flanked by three extended fibers I and six trimeric fibers II. Conformational changes of fiber II in DNA-ejected VP1 may cause the release of the tail needle and core proteins, forming an elongated tail channel. Our structures provide insights into the molecular mechanisms of infection and DNA release for podophages with a tail needle.

Mathematical modeling of cholera dynamics in the presence of antimicrobial utilization strategy

Antimicrobial resistance poses a significant threat to public health, particularly in cholera treatment. The emergence of antibiotic resistance, coupled with the sharp decline in pharmaceutical companies developing new cholera antibiotics, is a cause for concern. We formulate a multidrug-resistant (MDR) cholera epidemic model that incorporates a stage-switching strategy between two antibiotics to reduce the magnitude of resistance. The model is analyzed mathematically, and sensitivity analysis of the reproduction number is performed using sub-reproduction numbers. Stability analysis of the cholera-sensitive-only and cholera-resistant-only equilibria is investigated using Centre Manifold Theory. The model is calibrated through Markov Chain Monte Carlo simulations in Stan, showing stability at equilibrium points, which is further verified through numerical simulations. The simulations demonstrate an inverse relationship between the number of MDR cholera cases and the number of individuals receiving second-line treatment for cholera. This study suggests that the correct use of antibiotics can effectively manage the emergence of antimicrobial resistance. From a public health policy perspective, these findings emphasize the importance of antibiotic stewardship programs and the need for policies that promote the responsible use of existing antibiotics while encouraging the development of new treatment options. Such measures could help mitigate the global burden of MDR cholera and prevent further escalation of resistance.

Inferring the proportion of undetected cholera infections from serological and clinical surveillance in an immunologically naive population

Most infections with pandemic Vibrio cholerae are thought to result in subclinical disease and are not captured by surveillance. Previous estimates of the ratio of infections to clinical cases have varied widely (2 to 100 infections per case). Understanding cholera epidemiology and immunity relies on the ability to translate between numbers of clinical cases and the underlying number of infections in the population. We estimated the infection incidence during the first months of an outbreak in a cholera-naive population using a Bayesian vibriocidal antibody titer decay model combining measurements from a representative serosurvey and clinical surveillance data. 3,880 suspected cases were reported in Grande Saline, Haiti, between 20 October 2010 and 6 April 2011 (clinical attack rate 18.4%). We found that more than 52.6% (95% Credible Interval (CrI) 49.4-55.7) of the population ≥2 years showed serologic evidence of infection, with a lower infection rate among children aged 2-4 years (35.5%; 95%CrI 24.2-51.6) compared with people ≥5 years (53.1%; 95%CrI 49.4-56.4). This estimated infection rate, nearly three times the clinical attack rate, with underdetection mainly seen in those ≥5 years, has likely impacted subsequent outbreak dynamics. Our findings show how seroincidence estimates improve understanding of links between cholera burden, transmission dynamics and immunity.

Wastewater-based surveillance of Vibrio cholerae: Molecular insights on biofilm regulatory diguanylate cyclases, virulence factors and antibiotic resistance patterns

Vibrio cholerae is an inherent inhabitant of aquatic ecosystems. The Indian state of West Bengal, especially the Gangetic delta region is the highest cholera affected region and is considered as the hub of Asiatic cholera. V. cholerae were isolated from publicly accessible wastewater of Midnapore, West Bengal, India. Serotyping determined all isolates to be of non-O1/non-O139 serogroups. Moderate biofilm-forming abilities were noticed in most of the isolates (74.7 %) while, high biofilm formation was recorded for only 6.3 % isolates and 19 % of isolates exhibited low/non-biofilm-forming abilities. PCR-based screening of crucial diguanylate cyclases (DGCs) involved in cyclic-di-GMP-mediated biofilm signaling was performed. cdgH and cdgM were the most abundant DGCs among 93.7 % and 91.5 % of isolates, respectively. Other important DGCs, i.e., cdgK, cdgA, cdgL, and vpvC were present in 84 %, 75.5 %, 72 % and 68 % of isolates, respectively. Besides, the non-O1/non-O139 isolates were screened for the occurrence of virulence factor encoding genes. Moreover, among these non-O1/non-O139 isolates, two strains (3.17 %) harbored both ctxA and ctxB genes, which encode the cholera toxin associated with epidemic cholera. ompU was the most prevalent virulence factor, present in 24.8 % of isolates. Other virulence factors like, zot and st were found in 4.7 % and 9.5 % of isolates. Genes encoding tcp and ace were found to be PCR-negative for the isolates. Additionally, crucial virulence factor regulators, toxT, toxR and hapR were found to be PCR-positive in all the isolates. Antibiotic resistance patterns displayed further vulnerabilities with decreased sensitivity towards commonly used antibiotics with multiple antibiotic resistance index ranging between 0.37 and 0.62. The presence of cholera toxin-encoding multi-drug resistant (MDR) V. cholerae strains in environmental settings is alarming. High occurrence of DGCs are considered to encourage further investigations to use them as alternative therapeutic targets against MDR cholera pathogen due to their unique presence in bacterial systems.

Genomic evidence of two-staged transmission of the early seventh cholera pandemic

The seventh cholera pandemic started in 1961 in Indonesia and spread across the world in three waves in the decades that followed. Here, we utilised genomic evidence to detail the first wave of the seventh pandemic. Genomes of 22 seventh pandemic Vibrio cholerae isolates from 1961 to 1979 were completely sequenced. Together with 152 publicly available genomes from the same period, they fell into seven phylogenetic clusters (CL1-CL7). By multilevel genome typing (MGT), all were assigned to MGT2 ST1 (Wave 1) except three isolates in CL7 which were typed as MGT2 ST2 (Wave 2). The Wave 1 seventh pandemic expanded in two stages, with Stage 1 (CL1-CL5) spread across Asia and Stage 2 (CL6 and CL7) spread to the Middle East and Africa. Three non-synonymous mutations, one each, in three regulatory genes, csrD (global regulator), acfB (chemotaxis), and luxO (quorum sensing) may have critically contributed to its pandemicity. The three MGT2 ST2 isolates in CL7 were the progenitors of Wave 2 and evolved from within Wave 1 with acquisition of a novel IncA/C plasmid. Our findings provide new insight into the evolution and transmission of the early seventh pandemic, which may aid future cholera prevention and control.

Variations in the Antivirulence Effects of Fatty Acids and Virstatin against Vibrio cholerae Strains

The expression of two major virulence factors of Vibrio cholerae, cholera toxin (CT) and toxin co-regulated pilus (TCP), is induced by environmental stimuli through a cascade of interactions among regulatory proteins known as the ToxR regulon when the bacteria reach the human small intestine. ToxT is produced via the ToxR regulon and acts as the direct transcriptional activator of CT (ctxAB), TCP (tcp gene cluster), and other virulence genes. Unsaturated fatty acids (UFAs) and several small-molecule inhibitors of ToxT have been developed as antivirulence agents against V. cholerae. This study reports the inhibitory effects of fatty acids and virstatin (a small-molecule inhibitor of ToxT) on the transcriptional activation functions of ToxT in isogenic derivatives of V. cholerae strains containing various toxT alleles. The fatty acids and virstatin had discrete effects depending on the ToxT allele (different by 2 amino acids), V. cholerae strain, and culture conditions, indicating that V. cholerae strains could overcome the effects of UFAs and small-molecule inhibitors by acquiring point mutations in toxT. Our results suggest that small-molecule inhibitors should be examined thoroughly against various V. cholerae strains and toxT alleles during development.

Core and accessory genomic traits of Vibrio cholerae O1 drive lineage transmission and disease severity

In Bangladesh, Vibrio cholerae lineages are undergoing genomic evolution, with increased virulence and spreading ability. However, our understanding of the genomic determinants influencing lineage transmission and disease severity remains incomplete. Here, we developed a computational framework using machine-learning, genome scale metabolic modelling (GSSM) and 3D structural analysis, to identify V. cholerae genomic traits linked to lineage transmission and disease severity. We analysed in-patients isolates from six Bangladeshi regions (2015-2021), and uncovered accessory genes and core SNPs unique to the most recent dominant lineage, with virulence, motility and bacteriophage resistance functions. We also found a strong correlation between V. cholerae genomic traits and disease severity, with some traits overlapping those driving lineage transmission. GSMM and 3D structure analysis unveiled a complex interplay between transcription regulation, protein interaction and stability, and metabolic networks, associated to lifestyle adaptation, intestinal colonization, acid tolerance and symptom severity. Our findings support advancing therapeutics and targeted interventions to mitigate cholera spread.

Cholera outbreak in a rural south - south Nigerian community: A case-control study

Background

Cholera remains a disease of public health importance in Nigeria associated with high morbidity and mortality. On the 4th of June 2024, the Nigeria center for disease and control prevention (NCDC) through the Disease Surveillance and Notification Officer (DSNO) reported an increase in the number of reported cases of vomiting and diarrhea in Toru-Orua village, Sagbama Local Government Area Council, Bayelsa State, Nigeria. A team of researchers were deployed to investigate the outbreak with the objectives of verifying the diagnosis, identifying risk factors and instituting appropriate control measures to control the outbreak.

Methodology

We conducted a case-control study. We defined a cholera case as any person aged ≥5 years with acute watery diarrhea in Toru - Orua community. We identified community controls. A total of 93 cases and 118 controls were recruited. Structured questionnaires were administered to both cases and controls. Four stool samples from case-patients and two water samples from the community water source were collected for laboratory investigation. We performed univariate and bivariate analysis using Epi-Info version.

Results

The mean age of cases and controls was 20.3 years and 25.4 respectively (p value 0.09). Females constituted 50% (cases) and 60% (controls). The attack rate was 4.3% with a case fatality rate of 13%. Four stool (100%) specimen tested positive for Vibrio cholerae. The water source and environment were polluted by indiscriminate defecation. Compared to controls, cases were more likely to have drunk from the river forcados (OR 14.2, 95% CI: 5.5-36.8) and living in households (HH) with more than 5 persons/HH (OR 5.9, 95% CI: 1.3-27.2). Good hand hygiene was found to be protective (OR 0.3, 95% CI: 0.1-0.7).

Conclusion

Vibrio cholerae was the cause of the outbreak in Toru - Orua. Drinking water from river forcados, living in overcrowded HH and poor hand hygiene were significantly associated with the outbreak. We initiated hand hygiene and water treatment to control the outbreak.

Amoebae as training grounds for microbial pathogens

Grazing of amoebae on microorganisms represents one of the oldest predator-prey dynamic relationships in nature. It represents a genetic "melting pot" for an ancient and continuous multi-directional inter- and intra-kingdom horizontal gene transfer between amoebae and its preys, intracellular microbial residents, endosymbionts, and giant viruses, which has shaped the evolution, selection, and adaptation of microbes that evade degradation by predatory amoeba. Unicellular phagocytic amoebae are thought to be the ancient ancestors of macrophages with highly conserved eukaryotic processes. Selection and evolution of microbes within amoeba through their evolution to target highly conserved eukaryotic processes have facilitated the expansion of their host range to mammals, causing various infectious diseases. Legionella and environmental Chlamydia harbor an immense number of eukaryotic-like proteins that are involved in ubiquitin-related processes or are tandem repeats-containing proteins involved in protein-protein and protein-chromatin interactions. Some of these eukaryotic-like proteins exhibit novel domain architecture and novel enzymatic functions absent in mammalian cells, such as ubiquitin ligases, likely acquired from amoebae. Mammalian cells and amoebae may respond similarly to microbial factors that target highly conserved eukaryotic processes, but mammalian cells may undergo an accidental response to amoeba-adapted microbial factors. We discuss specific examples of microbes that have evolved to evade amoeba predation, including the bacterial pathogens- Legionella, Chlamydia, Coxiella, Rickettssia, Francisella, Mycobacteria, Salmonella, Bartonella, Rhodococcus, Pseudomonas, Vibrio, Helicobacter, Campylobacter, and Aliarcobacter. We also discuss the fungi Cryptococcus, and Asperigillus, as well as amoebae mimiviruses/giant viruses. We propose that amoeba-microbe interactions will continue to be a major "training ground" for the evolution, selection, adaptation, and emergence of microbial pathogens equipped with unique pathogenic tools to infect mammalian hosts. However, our progress will continue to be highly dependent on additional genomic, biochemical, and cellular data of unicellular eukaryotes.

Vibrio cholerae O1 experiences mild bottlenecks through the gastrointestinal tract in some but not all cholera patients

Vibrio cholerae O1 causes the diarrheal disease cholera, and the small intestine is the site of active infection. During cholera, cholera toxin is secreted from V. cholerae and induces a massive fluid influx into the small intestine, which causes vomiting and diarrhea. Typically, V. cholerae genomes are sequenced from bacteria passed in stool, but rarely from vomit, a fluid that may more closely represents the site of active infection. We hypothesized that V. cholerae O1 population bottlenecks along the gastrointestinal tract would result in reduced genetic variation in stool compared to vomit. To test this, we sequenced V. cholerae genomes from 10 cholera patients with paired vomit and stool samples. Genetic diversity was low in both vomit and stool, consistent with a single infecting population rather than coinfection with divergent V. cholerae O1 lineages. The amount of single-nucleotide variation decreased from vomit to stool in four patients, increased in two, and remained unchanged in four. The variation in gene presence/absence decreased between vomit and stool in eight patients and increased in two. Pangenome analysis of assembled short-read sequencing demonstrated that the toxin-coregulated pilus operon more frequently contained deletions in genomes from vomit compared to stool. However, these deletions were not detected by PCR or long-read sequencing, indicating that interpreting gene presence or absence patterns from short-read data alone may be incomplete. Overall, we found that V. cholerae O1 isolated from stool is genetically similar to V. cholerae recovered from the upper intestinal tract.

IMPORTANCE

Vibrio cholerae O1, the bacterium that causes cholera, is ingested in contaminated food or water and then colonizes the upper small intestine and is excreted in stool. Shed V. cholerae genomes from stool are usually studied, but V. cholerae isolated from vomit may be more representative of where V. cholerae colonizes in the upper intestinal epithelium. V. cholerae may experience bottlenecks, or large reductions in bacterial population sizes and genetic diversity, as it passes through the gut. Passage through the gut may select for distinct V. cholerae mutants that are adapted for survival and gut colonization. We did not find strong evidence for such adaptive mutations, and instead observed that passage through the gut results in modest reductions in V. cholerae genetic diversity, and only in some patients. These results fill a gap in our understanding of the V. cholerae life cycle, transmission, and evolution.

DdmABC-dependent death triggered by viral palindromic DNA sequences

Defense systems that recognize viruses provide important insights into both prokaryotic and eukaryotic innate immunity mechanisms. Such systems that restrict foreign DNA or trigger cell death have recently been recognized, but the molecular signals that activate many of these remain largely unknown. Here, we characterize one such system in pandemic Vibrio cholerae responsible for triggering cell density-dependent death (CDD) of cells in response to the presence of certain genetic elements. We show that the key component is the Lamassu DdmABC anti-phage/plasmid defense system. We demonstrate that signals that trigger CDD were palindromic DNA sequences in phages and plasmids that are predicted to form stem-loop hairpins from single-stranded DNA. Our results suggest that agents that damage DNA also trigger DdmABC activation and inhibit cell growth. Thus, any infectious process that results in damaged DNA, particularly during DNA replication, can in theory trigger DNA restriction and death through the DdmABC abortive infection system.

Elucidation of cellular signaling mechanism involved in Vibrio cholerae chitin-binding protein GbpA mediated IL-8 secretion in the intestinal cells

Background

Vibrio cholerae N-acetylglucosamine-binding protein (GbpA) is a four-domain, secretory colonization factor which is essential for chitin utilization in the environment, as well as in adherence to intestinal cells. GbpA is also involved in inducing intestinal inflammation by enhancing mucin and interleukin-8 secretion. The underlying cell signaling mechanism involved in the induction of the pro-inflammatory response and IL-8 secretion has yet to be deciphered in detail.

Methods

Herein, the process through which GbpA triggers the induction of IL-8 in intestinal cells was investigated by examining the role of GbpA in intestinal cell line HT 29.

Results

GbpA, specifically through the fourth domain, forms a binding connection with Toll-like receptor 2 (TLR2) and additionally, recruits TLR1 along with CD14 within a lipid raft micro-domain to initiate the signaling pathway. Notably, disruption of this micro-domain complex resulted in a reduction in IL-8 secretion. The lipid raft association served as the catalyst that invoked a downstream cellular inflammatory signaling pathway. This cascade involved the activation of various MAP kinases and NFκB and assembly of the AP-1 complex. This coordinated activation of signaling molecules eventually leads to enhanced IL-8 transcription via increased promoter activity. These findings suggested that GbpA is a crucial protein in V. cholerae, capable of inciting a pro-inflammatory response during infection by orchestrating the formation of the GbpA-TLR1/2-CD14 lipid raft complex. Activation of AP-1 and NFκB in the nucleus eventually enhanced IL-8 transcription through increased promoter activity.

Conclusion

Collectively, these findings indicated that GbpA plays a pivotal role within V. cholerae by triggering a pro-inflammatory response during infection. This response is instrumented by the formation of the GbpA-TLR1/2-CD14 lipid raft complex.

Recent developments of agents targeting Vibrio cholerae: patents and literature data

INTRODUCTION

Vibrio cholerae bacteria cause an infection characterized by acute diarrheal illness in the intestine. Cholera is sustained by people swallowing contaminated food or water. Even though symptoms can be mild, if untreated disease becomes severe and life-threatening, especially in low-income countries.

AREAS COVERED

After a description of the most recent literature on the pathophysiology of this infection, we searched for patents and literature articles following the PRISMA guidelines, filtering the results disclosed from 2020 to present. Moreover, some innovative molecular targets (e.g., carbonic anhydrases) and pathways to counteract this rising problem were also discussed in terms of design, structure-activity relationships and structural analyses.

EXPERT OPINION

This review aims to cover and analyze the most recent advances on the new druggable targets and bioactive compounds against this fastidious pathogen, overcoming the use of old antibiotics which currently suffer from high resistance rate.

Cholera rages in Africa and the Middle East: A narrative review on challenges and solutions

Background and Aim

Cholera is a life-threatening infectious disease that is still one of the most common acute watery diarrheal diseases in the world today. Acute diarrhea and severe dehydration brought on by cholera can cause hypovolemic shock, which can be fatal in minutes. Without competent clinical therapy, the rate of case fatality surpasses 50%. The purpose of this review was to highlight cholera challenges in Africa and the Middle East and explain the reasons for why this region is currently a fertile environment for cholera. We investigated cholera serology, epidemiology, and the geographical distribution of cholera in Africa and the Middle East in 2022 and 2023. We reviewed detection methods, such as rapid diagnostic tests (RDTs), and treatments, such as antibiotics and phage therapy. Finally, this review explored oral cholera vaccines (OCVs), and the vaccine shortage crisis.

Methods

We carried out a systematic search in multiple databases, including PubMed, Web of Science, Google Scholar, Scopus, MEDLINE, and Embase, for studies on cholera using the following keywords: ((Cholera) OR (Vibrio cholera) and (Coronavirus) OR (COVID-19) OR (SARS-CoV2) OR (The Middle East) OR (Africa)).

Results and Conclusions

Cholera outbreaks have increased dramatically, mainly in Africa and many Middle Eastern countries. The COVID-19 pandemic has reduced the attention devoted to cholera and disrupted diagnosis and treatment services, as well as vaccination initiatives. Most of the cholera cases in Africa and the Middle East were reported in Malawi and Syria, respectively, in 2022. RDTs are effective in the early detection of cholera epidemics, especially with limited advanced resources, which is the case in much of Africa. By offering both direct and indirect protection, expanding the use of OCV will significantly reduce the burden of current cholera outbreaks in Africa and the Middle East.

Spatiotemporal dynamics of cholera epidemics in Ethiopia: 2015-2021

Since the onset of the seventh cholera pandemic, Ethiopia has been affected by recurrent epidemics. However, the epidemiology of cholera in this country remains poorly understood. This study aimed to describe cholera outbreak characteristics in Ethiopia from 2015 to 2021. During this period, Ethiopia experienced four epidemic waves. The first wave involved nationwide outbreaks during the second half of 2016 followed by outbreaks predominantly affecting Somali Region in 2017. The second wave primarily affected Tigray and Afar Regions. During the third wave, multiple smaller-scale outbreaks occurred during 2019. The fourth wave was limited to Bale Zone (Oromia Region) in 2021. Overall, a north to south shift was observed over the course of the study period. Major cholera transmission factors included limited access to safe water and sanitation facilities. Severe weather events (drought and flooding) appear to aggravate cholera diffusion. Cholera transmission between Ethiopia and nearby countries (Kenya and Somalia), likely plays a major role in regional cholera dynamics. Overall, this study provides the first understanding of recent spatiotemporal cholera dynamics in Ethiopia to inform cholera control and elimination strategies.

Comparison of analysis methods to classify cholera hotspots in Ethiopia from 2015 to 2021

Cholera continues to represent a major public health concern in Ethiopia. The country has developed a Multi-sectoral National Cholera Elimination Plan in 2022, which targets prevention and control interventions in cholera hotspots. Multiple methods to classify cholera hotspots have been used in several countries. Since 2014, a classification method developed by United Nations Children's Fund has been applied to guide water, sanitation and hygiene interventions throughout Sub-Saharan Africa based on three outbreak parameters: frequency, duration and standardized attack rate. In 2019, the Global Task Force on Cholera Control (GTFCC) proposed a method based on two parameters: average annual cholera incidence and persistence. In 2023, an updated GTFCC method for multisectoral interventions considers three epidemiological indicators (cumulative incidence, cumulative mortality and persistence,) and a cholera-case confirmation indicator. The current study aimed to classify cholera hotspots in Ethiopia at the woreda level (equivalent to district level) applying the three methods and comparing the results to optimize the hotspot targeting strategy. From 2015 to 2021, cholera hotspots were located along major routes between Addis Ababa and woredas adjacent to the Kenya and Somalia borders, throughout Tigray Region, around Lake Tana, and in Afar Region. The multi-method comparison enables decision makers to prioritize interventions according to a sub-classification of the highest-priority areas.

Deployment of a Vibrio cholerae ordered transposon mutant library in a quorum-competent genetic background

Vibrio cholerae, the causative agent of cholera, has sparked seven pandemics in recent centuries, with the current one being the most prolonged. V. cholerae's pathogenesis hinges on its ability to switch between low and high cell density gene regulatory states, enabling transmission between host and the environment. Previously, a transposon mutant library for V. cholerae was created to support investigations aimed toward uncovering the genetic determinants of its pathogenesis. However, subsequent sequencing uncovered a mutation in the gene luxO of the parent strain, rendering mutants unable to exhibit high cell density behaviors. In this study, we used chitin-independent natural transformation to move transposon insertions from these low cell density mutants into a wildtype genomic background. Library transfer was aided by a novel gDNA extraction we developed using thymol, which also showed high lysis-specificity for Vibrio. The resulting Grant Library comprises 3,102 unique transposon mutants, covering 79.8% of V. cholerae's open reading frames. Whole genome sequencing of randomly selected mutants demonstrates 100% precision in transposon transfer to cognate genomic positions of the recipient strain. Notably, in no instance did the luxO mutation transfer into the wildtype background. Our research uncovered density-dependent epistasis in growth on inosine, an immunomodulatory metabolite secreted by gut bacteria that is implicated in enhancing gut barrier functions. Additionally, Grant Library mutants retain the plasmid that enables rapid, scarless genomic editing. In summary, the Grant Library reintroduces organismal relevant genetic contexts absent in the low cell density locked library equivalent.

Spatiotemporal dynamics of cholera hotspots in the Democratic Republic of the Congo from 1973 to 2022

BACKGROUND

Since the early 1970s, cholera outbreaks have been a major public health burden in the Democratic Republic of Congo (DRC). Cholera cases have been reported in a quasi-continuous manner in certain lakeside areas in the Great Lakes Region. As these cholera-endemic health zones constitute a starting point for outbreaks and diffusion towards other at-risk areas, they play a major role in cholera dynamics in the country. Monitoring the spatiotemporal dynamics of cholera hotspots and adjusting interventions accordingly thus reduces the disease burden in an efficient and cost-effective manner.

METHODS

A literature review was conducted to describe the spatiotemporal dynamics of cholera in the DRC at the province level from 1973 to 1999. We then identified and classified cholera hotspots at the provincial and health zone levels from 2003 to 2022 and described the spatiotemporal evolution of hotspots. We also applied and compared three different classification methods to ensure that cholera hotspots are identified and classified according to the DRC context.

RESULTS

According to all three methods, high-priority hotspots were concentrated in the eastern Great Lakes Region. Overall, hotspots largely remained unchanged over the course of the study period, although slight improvements were observed in some eastern hotspots, while other non-endemic areas in the west experienced an increase in cholera outbreaks. The Global Task Force on Cholera Control (GTFCC) and the Department of Ecology and Infectious Disease Control (DEIDC) methods largely yielded similar results for the high-risk hotspots. However, the medium-priority hotspots identified by the GTFCC method were further sub-classified by the DEIDC method, thereby providing a more detailed ranking for priority targeting.

CONCLUSIONS

Overall, the findings of this comprehensive study shed light on the dynamics of cholera hotspots in the DRC from 1973 to 2022. These results may serve as an evidence-based foundation for public health officials and policymakers to improve the implementation of the Multisectoral Cholera Elimination Plan, guiding targeted interventions and resource allocation to mitigate the impact of cholera in vulnerable communities.

Diversity of Vibrio cholerae O1 through the human gastrointestinal tract during cholera

Vibrio cholerae O1 causes the diarrheal disease cholera, and the small intestine is the site of active infection. During cholera, cholera toxin is secreted from V. cholerae and induces a massive fluid influx into the small intestine, which causes vomiting and diarrhea. Typically, V. cholerae genomes are sequenced from bacteria passed in stool, but rarely from vomit, a fluid that may more closely represents the site of active infection. We hypothesized that the V. cholerae O1 population bottlenecks along the gastrointestinal tract would result in reduced genetic variation in stool compared to vomit. To test this, we sequenced V. cholerae genomes from ten cholera patients with paired vomit and stool samples. Genetic diversity was low in both vomit and stool, consistent with a single infecting population rather than co-infection with divergent V. cholerae O1 lineages. The number of single nucleotide variants decreased between vomit and stool in four patients, increased in two, and remained unchanged in four. The number of genes encoded in the V. cholerae genome decreased between vomit and stool in eight patients and increased in two. Pangenome analysis of assembled short-read sequencing demonstrated that the toxin-coregulated pilus operon more frequently contained deletions in genomes from vomit compared to stool. However, these deletions were not detected by PCR or long-read sequencing, indicating that interpreting gene presence or absence patterns from short-read data alone may be incomplete. Overall, we found that V. cholerae O1 isolated from stool is genetically similar to V. cholerae recovered from the upper intestinal tract.

The incidence, and spatial trends of cholera in Sabah over 15 years: Repeated outbreaks in coastal areas

Vibrio cholerae remains a notable public health challenge across Malaysia. Although the Malaysian state of Sabah is considered a cholera-affected area, gaps remain in understanding the epidemiological trends and spatial distribution of outbreaks. Therefore, to determine longitudinal and spatial trends in cholera cases data were obtained from the Sabah State Health Department for all notified cases of cholera between 2005-2020. A cholera outbreak is defined as one or more confirmed cases in a single locality with the evidence of local transmission. All records were geolocated to village level. Satellite-derived data and generalised linearized models were used to assess potential risk factors, including population density, elevation, and distance to the sea. Spatiotemporal clustering of reported cholera cases and zones of increased cholera risk were evaluated using the tau statistic (τ) at 550m, 5km and 10km distances. Over a 15-year period between 2005-2020, 2865 cholera cases were recorded in Sabah, with a mean incidence rate of 5.6 cases per 100,000 (95% CI: 3.4-7.9). From 2015-2020, 705 symptomatic cases and 727 asymptomatic cases were reported. Symptomatic cases primarily occurred in local Malaysian populations (62.6%, 441/705) and in children and adolescents under 15-years old (49.4%, 348/705). On average, cases were reported in areas with low population density (19.45 persons/km2), low elevations (19.45m) and near coastal areas. Spatiotemporal clustering of cholera cases was identified up to 3.5km, with increased village-level cholera risk within 500m and 5 days of initial case presentation to a health facility (Risk Ratio = 9.7, 95% CI: 7.5-12.4). Cholera incidence has high spatial and temporal heterogeneity within Sabah, with some districts experiencing repeated outbreaks. Cholera cases clustered across space and time, with village-level risk of cholera highest within 5 days and within close proximity to primary case villages, suggesting local transmission.

Safeguarding drinking water: A brief insight on characteristics, treatments and risk assessment of contamination

Water pollution stands as a critical worldwide concern, bearing extensive repercussions that extend to human health and the natural ecosystem. The sources of water pollution can be diverse, arising from natural processes and human activities and the pollutants may range from chemical and biological agents to physical and radiological contaminants. The contamination of water disrupts the natural functioning of the system, leading to both immediate and prolonged health problems. Various technologies and procedures, ranging from conventional to advanced, have been developed to eliminate water impurities, with the choice depending on the type and level of contamination. Assessing risks is a crucial element in guaranteeing the safety of drinking water. Till now, research is continuing the removal of contaminates for the sake of supplying safe drinking water. The study examined physical, inorganic, organic, biological and radiological contaminants in drinking water. It looked at where these contaminants come from, their characteristics, the impact they have and successful methods used in real-world situations to clean the contaminated water. Risk assessment methodologies associated with the use of unsafe drinking water as future directives are also taken into consideration in the present study for the benefit of public concern. The manuscript introduces a comprehensive study on water pollution, focusing on assessing and mitigating risks associated with physical, inorganic, organic, biological and radiological contaminants in drinking water, with a novel emphasis on future directives and sustainable solutions for public safety.

Genomic and functional insights into antibiotic resistance genes floR and strA linked with the SXT element of Vibrio cholerae non-O1/non-O139

The emergence and spread of antibiotic-resistant bacterial pathogens are a critical public health concern across the globe. Mobile genetic elements (MGEs) play an important role in the horizontal acquisition of antimicrobial resistance genes (ARGs) in bacteria. In this study, we have decoded the whole genome sequences of multidrug-resistant Vibrio cholerae clinical isolates carrying the ARG-linked SXT, an integrative and conjugative element, in their large chromosomes. As in others, the SXT element has been found integrated into the 5'-end of the prfC gene (which encodes peptide chain release factor 3 involved in translational regulation) on the large chromosome of V. cholerae non-O1/non-O139 strains. Further, we demonstrate the functionality of SXT-linked floR and strAB genes, which confer resistance to chloramphenicol and streptomycin, respectively. The floR gene-encoded protein FloR belongs to the major facilitator superfamily efflux transporter containing 12 transmembrane domains (TMDs). Deletion analysis confirmed that even a single TMD of FloR is critical for the export function of chloramphenicol. The floR gene has two putative promoters, P1 and P2. Sequential deletions reveal that P2 is responsible for the expression of the floR. Deletion analysis of the N- and/or C-terminal coding regions of strA established their importance for conferring resistance against streptomycin. Interestingly, qPCR analysis of the floR and strA genes indicated that both of the genes are constitutively expressed in V. cholerae cells. Further, whole genome-based global phylogeography confirmed the presence of the integrative and conjugative element SXT in non-O1/non-O139 strains despite being non-multidrug resistant by lacking antimicrobial resistance (AMR) gene cassettes, which needs monitoring.

Benefits of Combining Molecular Biology and Controlled Human Infection Model Methodologies in Advancing Vaccine Development

Infectious diseases continue to account for a significant portion of global deaths despite the use of vaccines for several centuries. Immunization programs around the world are a testament to the great success of multiple vaccines, yet there are still diseases without vaccines and others that require safer more effective ones. Addressing uncontrolled and emerging disease threats is restrained by the limitations and bottlenecks encountered with traditional vaccine development paradigms. Recent advances in modern molecular biology technologies have enhanced the interrogation of host pathogen interaction and deciphered complex pathways, thereby uncovering the myriad interplay of biological events that generate immune protection against foreign agents. Consequent to insights into the immune system, modern biology has been instrumental in the development and production of next generation 21st century vaccines. As these biological tools, commonly and collectively referred to as 'omics, became readily available, there has been a renewed consideration of Controlled Human Infection Models (CHIMs). Successful and reproducible CHIMs can complement modern molecular biology for the study of infectious diseases and development of effective vaccines in a regulated process that mitigates risk, cost, and time, with capacity to discern immune correlates of protection.

The diverse landscape of AB5-type toxins

AB5-type toxins are a group of secreted protein toxins that are central virulence factors for bacterial pathogens such as Shigella dysenteriae, Vibrio cholerae, Bordetella pertussis, and certain lineages of pathogenic Escherichia coli and Salmonella enterica. AB5 toxins are composed of an active (A) subunit that manipulates host cell biology in complex with a pentameric binding/delivery (B) subunit that mediates the toxin's entry into host cells and its subsequent intracellular trafficking. Broadly speaking, all known AB5-type toxins adopt similar structural architectures and employ similar mechanisms of binding, entering and trafficking within host cells. Despite this, there is a remarkable amount of diversity amongst AB5-type toxins; this includes different toxin families with unrelated activities, as well as variation within families that can have profound functional consequences. In this review, we discuss the diversity that exists amongst characterized AB5-type toxins, with an emphasis on the genetic and functional variability within AB5 toxin families, how this may have evolved, and its impact on human disease.

Dynamics of efflux pumps in antimicrobial resistance, persistence, and community living of Vibrionaceae

The marine bacteria of the Vibrionaceae family are significant from the point of view of their role in the marine geochemical cycle, as well as symbionts and opportunistic pathogens of aquatic animals and humans. The well-known pathogens of this group, Vibrio cholerae, V. parahaemolyticus, and V. vulnificus, are responsible for significant morbidity and mortality associated with a range of infections from gastroenteritis to bacteremia acquired through the consumption of raw or undercooked seafood and exposure to seawater containing these pathogens. Although generally regarded as susceptible to commonly employed antibiotics, the antimicrobial resistance of Vibrio spp. has been on the rise in the last two decades, which has raised concern about future infections by these bacteria becoming increasingly challenging to treat. Diverse mechanisms of antimicrobial resistance have been discovered in pathogenic vibrios, the most important being the membrane efflux pumps, which contribute to antimicrobial resistance and their virulence, environmental fitness, and persistence through biofilm formation and quorum sensing. In this review, we discuss the evolution of antimicrobial resistance in pathogenic vibrios and some of the well-characterized efflux pumps' contributions to the physiology of antimicrobial resistance, host and environment survival, and their pathogenicity.

DegS protease regulates antioxidant capacity and adaptability to oxidative stress environment in Vibrio cholerae

Adaptation to oxidative stress is critical for survival of Vibrio cholerae in aquatic ecosystems and hosts. DegS activates the σE envelope stress response. We have previously revealed that DegS may be involved in regulating the oxidative stress response. In this study, we demonstrated that deletion of the degS gene attenuates the antioxidant capacity of V. cholerae. In addition, our results further revealed that the regulation of antioxidant capacity by DegS in V. cholerae could involve the cAMP-CRP complex, which regulates rpoS. XthA is an exonuclease that repairs oxidatively damaged cells and affects the bacterial antioxidant capacity. qRT-PCR showed that DegS, σE, cAMP, CRP, and RpoS positively regulate xthA gene transcription. XthA overexpression partially compensates for antioxidant deficiency in the degS mutant. These results suggest that DegS affects the antioxidant capacity of V.cholerae by regulating xthA expression via the cAMP-CRP-RpoS pathway. In a mouse intestinal colonization experiment, our data showed that V.cholerae degS, rpoE, and rpoS gene deletions were associated with significantly reduced resistance to oxidative stress and the ability to colonize the mouse intestine. In conclusion, these findings provide new insights into the regulation of antioxidant activity by V.cholerae DegS.

Inferring the proportion of undetected cholera infections from serological and clinical surveillance in an immunologically naive population

Most infections with pandemic Vibrio cholerae are thought to result in subclinical disease and are not captured by surveillance. Previous estimates of the ratio of infections to clinical cases have varied widely (2 to 100). Understanding cholera epidemiology and immunity relies on the ability to translate between numbers of clinical cases and the underlying number of infections in the population. We estimated the infection incidence during the first months of an outbreak in a cholera-naive population using a Bayesian vibriocidal antibody titer decay model combining measurements from a representative serosurvey and clinical surveillance data. 3,880 suspected cases were reported in Grande Saline, Haiti, between 20 October 2010 and 6 April 2011 (clinical attack rate 18.4%). We found that more than 52.6% (95% Credible Interval (CrI) 49.4-55.7) of the population ≥2 years showed serologic evidence of infection, with a lower infection rate among children aged 2-4 years (35.5%; 95%CrI 24.2-51.6) compared with people ≥5 years (53.1%; 95%CrI 49.4-56.4). This estimated infection rate, nearly three times the clinical attack rate, with underdetection mainly seen in those ≥5 years, has likely impacted subsequent outbreak dynamics. Our findings show how seroincidence estimates improve understanding of links between cholera burden, transmission dynamics and immunity.

Activation of a Vibrio cholerae CBASS anti-phage system by quorum sensing and folate depletion

IMPORTANCE

To counteract infection with phage, bacteria have evolved a myriad of molecular defense systems. Some of these systems initiate a process called abortive infection, in which the infected cell kills itself to prevent phage propagation. However, such systems must be inhibited in the absence of phage infection to prevent spurious death of the host. Here, we show that the cyclic oligonucleotide based anti-phage signaling system (CBASS) accomplishes this by sensing intracellular folate molecules and only expressing this system in a group. These results enhance our understanding of the evolution of the seventh Vibrio cholerae pandemic and more broadly how bacteria defend themselves against phage infection.

The Response Regulator VC1795 of Vibrio Pathogenicity Island-2 Contributes to Intestinal Colonization by Vibrio cholerae

Vibrio cholerae is an intestinal pathogen that can cause severe diarrheal disease. The disease has afflicted millions of people since the 19th century and has aroused global concern. The Vibrio Pathogenicity Island-2 (VPI-2) is a 57.3 kb region, VC1758-VC1809, which is present in choleragenic V. cholerae. At present, little is known about the function of VC1795 in the VPI-2 of V. cholerae. In this study, the intestinal colonization ability of the ΔVC1795 strain was significantly reduced compared to that of the wild-type strain, and the colonization ability was restored to the wild-type strain after VC1795 gene replacement. This result indicated that the VC1795 gene plays a key role in the intestinal colonization and pathogenicity of V. cholerae. Then, we explored the upstream and downstream regulation mechanisms of the VC1795 gene. Cyclic adenylate receptor protein (CRP) was identified as being located upstream of VC1795 by a DNA pull-down assay and electrophoretic mobility shift assays (EMSAs) and negatively regulating the expression of VC1795. In addition, the results of Chromatin immunoprecipitation followed by sequencing (ChIP-seq), EMSAs, and Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) indicated that VC1795 directly negatively regulates the expression of its downstream gene, VC1794. Furthermore, by using qRT-PCR, we hypothesized that VC1795 indirectly positively regulates the toxin-coregulated pilus (TCP) cluster to influence the colonization ability of V. cholerae in intestinal tracts. In short, our findings support the key regulatory role of VC1795 in bacterial pathogenesis as well as lay the groundwork for the further determination of the complex regulatory network of VC1795 in bacteria.

Expression of Cholera Toxin (CT) and the Toxin Co-Regulated Pilus (TCP) by Variants of ToxT in Vibrio cholerae Strains

The expression of the two major virulence genes of Vibrio cholerae-tcpA (the major subunit of the toxin co-regulated pilus) and ctxAB (cholera toxin)-is regulated by the ToxR regulon, which is triggered by environmental stimuli during infection within the human small intestine. Special culture methods are required to induce the expression of virulence genes in V. cholerae in the laboratory setting. In the present study, induction of the expression of virulence genes by two point mutations (65th and 139th amino acids) in toxT, which is produced by the ToxR regulon and activates the transcription of the virulence genes in V. cholerae, under laboratory culture conditions has been investigated. Each of the four toxT alleles assessed displayed different transcriptional activator functions in a given V. cholerae strain. Although the ToxR regulon has been known to not be expressed by El Tor biotype V. cholerae strains cultured under standard laboratory conditions, the variant toxT alleles that we assessed in this study enabled the expression virulence genes in El Tor biotype strains grown under simple culture conditions comprising shake culture in LB medium, suggesting that the regulation of virulence gene expression may be regulated more complexly than previously thought and may involve additional factors beyond the production of ToxT by the ToxR regulon.

The concern about main crises such as the Covid-19 pandemic, the war in Ukraine, and climate change's impact on energy-saving behavior

The number of crises experienced around the world forces people to reconsider and reassess various aspects of their lives. The energy crisis caused by the war in Ukraine and uncontrolled climate change revealed the importance of energy-saving behavior. Thus, the aim of this paper is to analyze the concerns about current crises such as the Covid-19 pandemic, the war in Ukraine, and climate change's impact on energy-saving behavior and changes in environmental concern. Referring to the survey conducted in Lithuania in 2022, where 1000 respondents participated, the results revealed that the war in Ukraine was the most concerning problem. The level of climate change concern was slightly lower. Meanwhile, the Covid-19 pandemic was the least important problem in Lithuania in 2022. Furthermore, respondents stated that the Covid-19 pandemic contributed to the changes in environmental concern and energy-saving actions more than the war in Ukraine did. Meanwhile, the Generalized Linear Model results revealed that only the war in Ukraine positively and significantly influenced energy-saving behavior. The Covid-19 pandemic concern negatively affected energy-saving behavior, while the climate change concern factor affected it indirectly, as the interaction of attitudes toward energy consumption. Thus, this study revealed the main aspect of and how to encourage energy-saving behavior in the context of the main current crises.

Advances in cholera research: from molecular biology to public health initiatives

The aquatic bacterium Vibrio cholerae is the etiological agent of the diarrheal disease cholera, which has plagued the world for centuries. This pathogen has been the subject of studies in a vast array of fields, from molecular biology to animal models for virulence activity to epidemiological disease transmission modeling. V. cholerae genetics and the activity of virulence genes determine the pathogenic potential of different strains, as well as provide a model for genomic evolution in the natural environment. While animal models for V. cholerae infection have been used for decades, recent advances in this area provide a well-rounded picture of nearly all aspects of V. cholerae interaction with both mammalian and non-mammalian hosts, encompassing colonization dynamics, pathogenesis, immunological responses, and transmission to naïve populations. Microbiome studies have become increasingly common as access and affordability of sequencing has improved, and these studies have revealed key factors in V. cholerae communication and competition with members of the gut microbiota. Despite a wealth of knowledge surrounding V. cholerae, the pathogen remains endemic in numerous countries and causes sporadic outbreaks elsewhere. Public health initiatives aim to prevent cholera outbreaks and provide prompt, effective relief in cases where prevention is not feasible. In this review, we describe recent advancements in cholera research in these areas to provide a more complete illustration of V. cholerae evolution as a microbe and significant global health threat, as well as how researchers are working to improve understanding and minimize impact of this pathogen on vulnerable populations.

Vibrio cholerae RND efflux systems: mediators of stress responses, colonization and pathogenesis

Resistance Nodulation Division (RND) efflux systems are ubiquitous transporters in gram-negative bacteria that provide protection against antimicrobial agents and thereby enhance survival in virtually all environments these prokaryotes inhabit. Vibrio cholerae is a dual lifestyle enteric pathogen that spends much of its existence in aquatic environments. An unwitting encounter with a human host can lead to V. cholerae intestinal colonization by strains that encode cholera toxin and toxin co-regulated pilus virulence factors leading to potentially fatal cholera diarrhea and dissemination in the environment. Adaptive response mechanisms to host factors encountered by these pathogens are therefore critical both to engage survival mechanisms such as RND-mediated transporters and to induce timely expression of virulence factors. Sensing of cues encountered in the host may therefore activate more than protective responses such as efflux systems, but also be coordinated to initiate expression of virulence factors. This review summarizes recent advances that contribute towards the understanding of RND efflux physiological functions and how the transport systems interface with the regulation of virulence factor production in V. cholerae.

Vibrio cholerae O1 associated with recent endemic cholera shows temporal changes in serotype, genotype, and drug-resistance patterns in Bangladesh

BACKGROUND

Despite the advancement in our understanding of cholera and its etiological agent, Vibrio cholerae, the prevention and treatment of the disease are often hindered due to rapid changes in drug response pattern, serotype, and the major genomic islands namely, the CTX-prophage, and related genetic characteristics. In the present study, V. cholerae (n = 172) associated with endemic cholera in Dhaka during the years 2015-2021 were analyzed for major phenotypic and genetic characteristics, including drug resistance patterns.

RESULTS

Results revealed that the V. cholerae strains belonged to serogroup O1 biotype El Tor carrying El Tor -specific genes rtxC, tcpA El Tor, and hlyA El Tor, but possessed classical-biotype cholera toxin. Serotypes of V. cholerae strains differed temporally in predominance with Inaba during 2015-2017, and again in 2020-2021, while Ogawa was the predominant serotype in 2018-2019. Also, ctxB1 was predominant in V. cholerae associated with cholera during 2015-2017, while ctxB7 was predominant in 2018, and in the subsequent years, as observed until 2021. V. cholerae strains differed in their antibiotic resistance pattern with a majority (97%) being multi-drug resistant (MDR) and belonging to six sub-groups. Notably, one of these MDR strains was resistant to eleven of the eighteen antibiotics tested, with resistance to fourth-generation cephalosporin (cefepime), and aztreonam. This extreme drug resistant (XDR) strain carried resistance-related genes namely, extended-spectrum β-lactamases (ESBL), blaOXA-1 and blaPER-3.

CONCLUSION

The observed temporal switching of serotypes, as well as the ctxB genotype, and the emergence of MDR/XDR V. cholerae and their association with endemic cholera in Dhaka underscore the need for routine monitoring of the pathogen for proper patient management.

Environmental water in Kolkata is suitable for the survival of Vibrio cholerae O1

Many patients with cholera emerge in Kolkata, India throughout the year. Such emergency indicates that cholera toxin-producing Vibrio cholerae O1 (toxigenic V. cholerae O1) are widespread in Kolkata. This suggests that the suitable conditions for replication of toxigenic V. cholerae O1 is provided in Kolkata. In previous studies, we found that the replication rate of toxigenic V. cholerae O1 is low in the low ionic aqueous solution. Then we measured the ion concentration in the environmental water of Kolkata. As a control, we measured them in Japanese environmental water. The ion concentration in the environmental water of Kolkata was significantly high. Then, we examined the survival of toxigenic V. cholerae O1 in groundwater from Kolkata and found that V. cholerae O1 survive for long time in the solution but not in the solution diluted with Milli Q water. In addition, we found that V. cholerae O1 proliferated in environmental water of Kolkata to which a small amount of nutrient was added, but did not grow in the environmental water diluted with water to which the same amount of nutrient was added. These results indicate that the environmental water from Kolkata is suitable for survival of V. cholerae O1.

Selection of G-rich ssDNA aptamers for the detection of enterotoxins of the cholera toxin family

Cholera and milder diarrheal disease are caused by Vibrio cholerae and enterotoxigenic Escherichia coli and are still a prominent public health concern. Evaluation of suspicious isolates is essential for the rapid containment of acute diarrhea outbreaks or prevention of epidemic cholera. Existing detection techniques require expensive equipment, trained personnel and are time-consuming. Antibody-based methods are also available, but cost and stability issues can limit their applications for point-of-care testing. This study focused on the selection of single stranded DNA aptamers as simpler, more stable and more cost-effective alternatives to antibodies for the co-detection of AB₅ toxins secreted by enterobacteria causing acute diarrheal infections. Cholera toxin and Escherichia coli heat-labile enterotoxin, the key toxigenicity biomarkers of these bacteria, were immobilized on magnetic beads and were used in a SELEX-based selection strategy. This led to the enrichment of sequences with a high % GC content and a dominant G-rich motif as revealed by Next Generation Sequencing. Enriched sequences were confirmed to fold into G-quadruplex structures and the binding of one of the most abundant candidates to the two enterotoxins was confirmed. Ongoing work is focused on the development of monitoring tools for potential environmental surveillance of epidemic choleraand milder diarrheal disease.

Environmental Reservoirs of Pathogenic Vibrio spp. and Their Role in Disease: The List Keeps Expanding

Vibrio species are natural inhabitants of aquatic environments and have complex interactions with the environment that drive the evolution of traits contributing to their survival. These traits may also contribute to their ability to invade or colonize animal and human hosts. In this review, we attempt to summarize the relationships of Vibrio spp. with other organisms in the aquatic environment and discuss how these interactions could potentially impact colonization of animal and human hosts.

Stress Responses in Pathogenic Vibrios and Their Role in Host and Environmental Survival

Vibrio is a genus of bacteria commonly found in estuarine, marine, and freshwater environments. Vibrio species have evolved to occupy diverse niches in the aquatic ecosystem, with some having complex lifestyles. About a dozen of the described Vibrio species have been reported to cause human disease, while many other species cause disease in other organisms. Vibrio cholerae causes epidemic cholera, a severe dehydrating diarrheal disease associated with the consumption of contaminated food or water. The human pathogenic non-cholera Vibrio species, Vibrio parahaemolyticus and Vibrio vulnificus, cause gastroenteritis, septicemia, and other extra-intestinal infections. Infections caused by V. parahaemolyticus and V. vulnificus are normally acquired through exposure to sea water or through consumption of raw or undercooked contaminated seafood. The human pathogenic Vibrios are exposed to numerous different stress-inducing agents and conditions in the aquatic environment and when colonizing a human host. Therefore, they have evolved a variety of mechanisms to survive in the presence of these stressors. Here we discuss what is known about important stress responses in pathogenic Vibrio species and their role in bacterial survival.