Cholera transmission: the host, pathogen and bacteriophage dynamic

Global and regional final point-of-drinking water prevalence of Vibrio pathogens: a systematic analysis with socioeconomic, global health security, and WASH indices-guided meta-regressions

The final point-of-drinking water (FPODW) exposure to Vibrio and waterborne pathogens remains a misaim surveillance target. Therefore, the current study purposed to estimate the global and regional prevalence of Vibrio pathogens in FPODW. Vibrio-FPODW data derived from integrated databases per PRISMA protocol were fitted to a random-intercept-logistic mixed-effects and meta-regression models. The global FPODW Vibrio prevalence was 5.13% (95%CI: 2.24-11.30) with 7.76% (6.84-8.78) cross-validated value. Vibrio prevalence in different FPODW varied with the highest in unclassified (13.98%, 3.98-38.95), household stored (6.42%, 1.16-28.69), municipal (4.39%, 1.54-11.90), and bottled (1.06%, 0.00-98.57) FPODW. Regionally, FPODW Vibrio prevalence varied significantly with highest in Africa (6.31%, 0.49-47.88), then Asia (4.83%, 2.01-11.18). Similarly, it varied significantly among income classification with the highest from low-income (8.77%, 0.91-50.05), then lower-middle-income (6.16%, 2.75-13.20), upper-middle-income (0.23%, 0.00-82.04), and 0.94% (0.19-2.72) in high-income economies. Among the WHO region, it varied significantly from 1.41% (0.17-10.45) in Eastern Mediterranean, 6.31% (0.49-47.88) in Africa to 8.86% (3.85-19.06) in South-East Asia and declining among SDI-quintiles from 11.64% (3.29-33.83) in Low-SDI, 10.59% (4.58-22.61) in High-middle-SDI to 0.26% (0.01-9.09) in Middle-SDI. FPODW Vibrio prevalence was 7.31% (2.94-17.03) in the low-GHSIG, followed by 4.55% (0.00-100.00) in the upper-GHSIG, and 2.21% (0.31-14.24) in middle-GHSIG; rural (4.18%, 0.06-76.17) and urban (5.28%, 2.35-11.44) settings. Also, sample size, SDI, SDI-quintiles, and nation significantly explained 14.12%, 10.91%, 30.35%, and 87.65% variance in FPODW Vibrio prevalence, respectively as a univariate influence. Additionally, 11.90% variance in FPODW Vibrio prevalence explained mortality rate attributed to unsafe WASH services. In conclusion, the study revealed a substantial high FPODW prevalence of Vibrio calling for initiative-taking and intentional surveillances of waterborne pathogens at the neglected stage across nations in order to achieve sustainably the SDG 3.

Genomic insights into the 2022-2023Vibrio cholerae outbreak in Malawi

Malawi experienced its deadliest Vibrio cholerae (Vc) outbreak following devastating cyclones, with >58,000 cases and >1700 deaths reported between March 2022 and May 2023. Here, we use population genomics to investigate the attributes and origin of the Malawi 2022-2023 Vc outbreak isolates. Our results demonstrate the predominance of ST69 clone, also known as the seventh cholera pandemic El Tor (7PET) lineage, expressing O1 Ogawa (~ 80%) serotype followed by Inaba (~ 16%) and sporadic non-O1/non-7PET serogroups (~ 4%). Phylogenetic reconstruction revealed that the Malawi outbreak strains correspond to a recent importation from Asia into Africa (sublineage AFR15). These isolates harboured known antimicrobial resistance and virulence elements, notably the ICEGEN/ICEVchHai1/ICEVchind5 SXT/R391-like integrative conjugative elements and a CTXφ prophage with the ctxB7 genotype compared to historical Malawian Vc isolates. These data suggest that the devastating cyclones coupled with the recent importation of 7PET serogroup O1 strains, may explain the magnitude of the 2022-2023 cholera outbreak in Malawi.

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.

An essential host dietary fatty acid promotes TcpH inhibition of TcpP proteolysis promoting virulence gene expression in Vibrio cholerae

Vibrio cholerae is a Gram-negative gastrointestinal pathogen responsible for the diarrheal disease cholera. Expression of key virulence factors, cholera toxin and toxin-coregulated pilus, is regulated directly by ToxT and indirectly by two transmembrane transcription regulators (TTRs), ToxR and TcpP, that promote the expression of toxT. TcpP abundance and activity are controlled by TcpH, a single-pass transmembrane protein, which protects TcpP from a two-step proteolytic process known as regulated intramembrane proteolysis (RIP). The mechanism of TcpH-mediated protection of TcpP represents a major gap in our understanding of V. cholerae pathogenesis. The absence of tcpH leads to unimpeded degradation of TcpP in vitro and a colonization defect in a neonate mouse model of V. cholerae colonization. Here, we show that TcpH protects TcpP from RIP via direct interaction. We also demonstrate that α-linolenic acid, a dietary fatty acid, promotes TcpH-dependent inhibition of RIP via co-association of TcpP and TcpH molecules within detergent-resistant membranes (DRMs) in a mechanism requiring the TcpH transmembrane domain. Taken together, our data support a model where V. cholerae cells use exogenous α-linolenic acid to remodel the phospholipid bilayer in vivo, leading to co-association of TcpP and TcpH within DRMs where RIP of TcpP is inhibited by TcpH, thereby promoting V. cholerae pathogenicity.

IMPORTANCE

Vibrio cholerae continues to pose a significant global burden on health and an alternative therapeutic approach is needed, due to evolving multidrug resistance strains. Transcription of toxT, stimulated by TcpP and ToxR, is essential for V. cholerae pathogenesis. Our results show that TcpP, one of the major regulators of toxT gene expression, is protected from proteolysis by TcpH, via direct interaction. Furthermore, we identified a gut metabolite, α-linolenic acid, that stimulates the co-association of TcpP and TcpH within detergent-resistant membranes (also known as lipid-ordered membrane domains), thereby supporting TcpH-dependent antagonism of TcpP proteolysis. Data presented here extend our knowledge of RIP, virulence gene regulation in V. cholerae, and, to the best of our knowledge, provides the first evidence that lipid-ordered membranes exist within V. cholerae. The model presented here also suggests that TTRs, common among bacteria and archaea, and co-component signal transduction systems present in Enterobacteria, could also be influenced similarly.

Multiple endemic equilibria in an environmentally-transmitted disease with three disease stages

We construct, analyze and interpret a mathematical model for an environmental transmitted disease characterized for the existence of three disease stages: acute, severe and asymptomatic. Besides, we consider that severe and asymptomatic cases may present relapse between them. Transmission dynamics driven by the contact rates only occurs when a parameter R∗>1, as normally occur in directly-transmitted or vector-transmitted diseases, but it will not adequately correspond to a basic reproductive number as it depends on environmental parameters. In this case, the forward transcritical bifurcation that exists for R∗<1, becomes a backward bifurcation, producing multiple steady-states, a hysteresis effect and dependence on initial conditions. A threshold parameter for an epidemic outbreak, independent of R∗ is only the ratio of the external contamination inflow shedding rate to the environmental clearance rate. R∗ describes the strength of the transmission to infectious classes other than the I-(acute) type infections. The epidemic outbreak conditions and the structure of R∗ appearing in this model are both responsible for the existence of endemic states.

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.

A Label-Free Colorimetric AuNP-Aptasensor for the Rapid Detection of Vibrio cholerae O139

Purpose

Waterborne pathogens pose a significant threat to public health, emphasizing the continuous necessity for advancing robust detection techniques, particularly in preventing outbreaks associated with these pathogens. This study focuses on cholera, an infectious disease caused by Vibrio cholerae, serogroups O1 and O139, often transmitted through contaminated water and food, raising significant public health concerns in areas with poor sanitation and limited access to clean water.

Methods

We developed a colorimetric biosensor using aptamer-functionalized gold nanoparticles to identify Vibrio cholerae O139 and address this issue. The detection mechanism relies on the color change of gold nanoparticles (AuNPs) from red to blue-purple induced by NaCl after the pathogen incubation and aptamer-target binding. Initial steps involved synthesizing and characterizing AuNPs, then exploring the impact of aptamer and NaCl concentrations on AuNP agglomeration. Optimization procedures for aptamer concentration and salt addition identified the optimal conditions for detection as 120 pM aptamers and 1 M NaCl.

Results

The aptasensor demonstrated a robust linear relationship, detecting V. cholerae concentrations from 103 to 108 CFU/mL, with a limit of detection (LOD) of 587 CFU/mL. Specificity tests and accurate sample analyses confirmed the efficiency of the AuNPs aptasensor, showcasing its reliability and speed compared to traditional culture examination methods. Moreover, we extended the aptasensor to a paper-based sensing platform with similar detection principles.

Conclusion

The change in color upon target binding was captured with a smartphone and analyzed using image processing software. The paper-based device detected the target in less than 2 min, demonstrating its convenience for on-field applications.

Lighting the way: how the Vibrio fischeri model microbe reveals the complexity of Earth's "simplest" life forms

Vibrio (Aliivibrio) fischeri's initial rise to fame derived from its alluring production of blue-green light. Subsequent studies to probe the mechanisms underlying this bioluminescence helped the field discover the phenomenon now known as quorum sensing. Orthologs of quorum-sensing regulators (i.e., LuxR and LuxI) originally identified in V. fischeri were subsequently uncovered in a plethora of bacterial species, and analogous pathways were found in yet others. Over the past three decades, the study of this microbe has greatly expanded to probe the unique role of V. fischeri as the exclusive symbiont of the light organ of the Hawaiian bobtail squid, Euprymna scolopes. Buoyed by this optically amenable host and by persistent and insightful researchers who have applied novel and cross-disciplinary approaches, V. fischeri has developed into a robust model for microbe-host associations. It has contributed to our understanding of how bacteria experience and respond to specific, often fluxing environmental conditions and the mechanisms by which bacteria impact the development of their host. It has also deepened our understanding of numerous microbial processes such as motility and chemotaxis, biofilm formation and dispersal, and bacterial competition, and of the relevance of specific bacterial genes in the context of colonizing an animal host. Parallels in these processes between this symbiont and bacteria studied as pathogens are readily apparent, demonstrating functional conservation across diverse associations and permitting a reinterpretation of "pathogenesis." Collectively, these advances built a foundation for microbiome studies and have positioned V. fischeri to continue to expand the frontiers of our understanding of the microbial world inside animals.

Flip bifurcation analysis and mathematical modeling of cholera disease by taking control measures

To study the dynamical system, it is necessary to formulate the mathematical model to understand the dynamics of various diseases which are spread in the world wide. The objective of the research study is to assess the early diagnosis and treatment of cholera virus by implementing remedial methods with and without the use of drugs. A mathematical model is built with the hypothesis of strengthening the immune system, and a ABC operator is employed to turn the model into a fractional-order model. A newly developed system SEIBR, which is examined both qualitatively and quantitatively to determine its stable position as well as the verification of flip bifurcation has been made for developed system. The local stability of this model has been explored concerning limited observations, a fundamental aspect of epidemic models. We have derived the reproductive number using next generation method, denoted as " R 0 ", to analyze its impact rate across various sub-compartments, which serves as a critical determinant of its community-wide transmission rate. The sensitivity analysis has been verified according to its each parameters to identify that how much rate of change of parameters are sensitive. Atangana-Toufik scheme is employed to find the solution for the developed system using different fractional values which is advanced tool for reliable bounded solution. Also the error analysis has been made for developed scheme. Simulations have been made to see the real behavior and effects of cholera disease with early detection and treatment by implementing remedial methods without the use of drugs in the community. Also identify the real situation the spread of cholera disease after implementing remedial methods with and without the use of drugs. Such type of investigation will be useful to investigate the spread of virus as well as helpful in developing control strategies from our justified outcomes.

Phage predation, disease severity, and pathogen genetic diversity in cholera patients

Despite an increasingly detailed picture of the molecular mechanisms of bacteriophage (phage)-bacterial interactions, we lack an understanding of how these interactions evolve and impact disease within patients. In this work, we report a year-long, nationwide study of diarrheal disease patients in Bangladesh. Among cholera patients, we quantified Vibrio cholerae (prey) and its virulent phages (predators) using metagenomics and quantitative polymerase chain reaction while accounting for antibiotic exposure using quantitative mass spectrometry. Virulent phage (ICP1) and antibiotics suppressed V. cholerae to varying degrees and were inversely associated with severe dehydration depending on resistance mechanisms. In the absence of antiphage defenses, predation was "effective," with a high predator:prey ratio that correlated with increased genetic diversity among the prey. In the presence of antiphage defenses, predation was "ineffective," with a lower predator:prey ratio that correlated with increased genetic diversity among the predators. Phage-bacteria coevolution within patients should therefore be considered in the deployment of phage-based therapies and diagnostics.

Phage predation, disease severity and pathogen genetic diversity in cholera patients

Despite an increasingly detailed picture of the molecular mechanisms of phage-bacterial interactions, we lack an understanding of how these interactions evolve and impact disease within patients. Here we report a year-long, nation-wide study of diarrheal disease patients in Bangladesh. Among cholera patients, we quantified Vibrio cholerae (prey) and its virulent phages (predators) using metagenomics and quantitative PCR, while accounting for antibiotic exposure using quantitative mass spectrometry. Virulent phage (ICP1) and antibiotics suppressed V. cholerae to varying degrees and were inversely associated with severe dehydration depending on resistance mechanisms. In the absence of anti-phage defenses, predation was 'effective,' with a high predator:prey ratio that correlated with increased genetic diversity among the prey. In the presence of anti-phage defenses, predation was 'ineffective,' with a lower predator:prey ratio that correlated with increased genetic diversity among the predators. Phage-bacteria coevolution within patients should therefore be considered in the deployment of phage-based therapies and diagnostics.

Clinical surveillance systems obscure the true cholera infection burden in an endemic region

Our understanding of cholera transmission and burden largely relies on clinic-based surveillance, which can obscure trends, bias burden estimates and limit the impact of targeted cholera-prevention measures. Serological surveillance provides a complementary approach to monitoring infections, although the link between serologically derived infections and medically attended disease incidence-shaped by immunological, behavioral and clinical factors-remains poorly understood. We unravel this cascade in a cholera-endemic Bangladeshi community by integrating clinic-based surveillance, healthcare-seeking and longitudinal serological data through statistical modeling. Combining the serological trajectories with a reconstructed incidence timeline of symptomatic cholera, we estimated an annual Vibrio cholerae O1 infection incidence rate of 535 per 1,000 population (95% credible interval 514-556), with incidence increasing by age group. Clinic-based surveillance alone underestimated the number of infections and reported cases were not consistently correlated with infection timing. Of the infections, 4 in 3,280 resulted in symptoms, only 1 of which was reported through the surveillance system. These results impart insights into cholera transmission dynamics and burden in the epicenter of the seventh cholera pandemic, where >50% of our study population had an annual V. cholerae O1 infection, and emphasize the potential for a biased view of disease burden and infection risk when depending solely on clinical surveillance data.

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.

In Vitro Models for Investigating Intestinal Host-Pathogen Interactions

Infectious diseases are increasingly recognized as a major threat worldwide due to the rise of antimicrobial resistance and the emergence of novel pathogens. In vitro models that can adequately mimic in vivo gastrointestinal physiology are in high demand to elucidate mechanisms behind pathogen infectivity, and to aid the design of effective preventive and therapeutic interventions. There exists a trade-off between simple and high throughput models and those that are more complex and physiologically relevant. The complexity of the model used shall be guided by the biological question to be addressed. This review provides an overview of the structure and function of the intestine and the models that are developed to emulate this. Conventional models are discussed in addition to emerging models which employ engineering principles to equip them with necessary advanced monitoring capabilities for intestinal host-pathogen interrogation. Limitations of current models and future perspectives on the field are presented.

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.

Metagenomics in the fight against zoonotic viral infections: A focus on SARS-CoV-2 analogues

Zoonotic viral infections continue to pose significant threats to global public health, as highlighted by the COVID-19 pandemic caused by the SARS-CoV-2 virus. The emergence of SARS-CoV-2 served as a stark reminder of the potential for zoonotic transmission of viruses from animals to humans. Understanding the origins and dynamics of zoonotic viruses is critical for early detection, prevention, and effective management of future outbreaks. Metagenomics has emerged as a powerful tool for investigating the virome of diverse ecosystems, shedding light on the diversity of viral populations, their hosts, and potential zoonotic spillover events. We provide an in-depth examination of metagenomic approaches, including, NGS metagenomics, shotgun metagenomics, viral metagenomics, and single-virus metagenomics, highlighting their strengths and limitations in identifying and characterizing zoonotic viral pathogens. This review underscores the pivotal role of metagenomics in enhancing our ability to detect, monitor, and mitigate zoonotic viral infections, using SARS-CoV-2 analogues as a case study. We emphasize the need for continued interdisciplinary collaboration among virologists, ecologists, and bioinformaticians to harness the full potential of metagenomic approaches in safeguarding public health against emerging zoonotic threats.

An Interesting Case of Asymptomatic Cholera in the Setting of Large Bowel Obstruction

Vibrio cholerae is the culprit behind many endemics globally. Classically characterized by profuse diarrhea with a "rice water" description, cholera can be fatal if not treated promptly. However, infected individuals can present with little to no symptoms. These individuals allow for a carrier state and play a large part in the survival of an endemic. Asymptomatic patients can present in areas where Cholera is not endemic. Herein, we present an atypical case of vibrio chloerae infection without diarrhea in the setting of large bowel obstruction secondary to colon cancer. We aim to highlight the unusual presentation of a cholera infection.

Edge-based compartmental modeling for the spread of cholera on random networks: A case study in Somalia

Cholera remains a major public health problem that threatens human health worldwide and its severity is continuing. In this paper, an edge-based model for cholera transmission on random networks is proposed and investigated. The model assumes that two communities share a common water source and includes three transmission routes, namely intra- and inter-community human-to-human transmission as well as water-to-human transmission. Intra-community human-to-human contacts are modeled through a random contact network, while both inter-community and water-to-human transmission are modeled through external nodes that reach each individual in the network to the same extent. The basic reproduction number and the equations of the final epidemic size are obtained. In addition, our study considers the cholera situation in Banadir, which is one of the most severely infected regions in Somalia, during the period (2019-2021). According to the geographical location, two adjacent districts are selected and our model fits well with the real data on the monthly cumulative cholera cases of these two districts during the above-mentioned period. From the perspective of network topology, cutting off high-risk contacts by supervising, isolating, quarantining and closing places with high-degree cholera-infected individuals to reduce degree heterogeneity is an effective measure to control cholera transmission. Our findings might offer some useful insights on cholera control.

Microbial Waterborne Diseases in India: Status, Interventions, and Future Perspectives

Water plays a vital role as a natural resource since life is unsustainable without it. If water is polluted or contaminated, it results in several health issues among people. Millions of people are infected with waterborne diseases globally, and India is no exception. In the present review, we have analyzed the outbreaks of waterborne diseases that occurred in several Indian states between 2014 and 2020, identified the key infections, and provided insights into the performance of sanitation improvement programs. We noted that acute diarrheal disease (ADD), typhoid, cholera, hepatitis, and shigellosis are common waterborne diseases in India. These diseases have caused about 11,728 deaths between 2014 and 2018 out of which 10,738 deaths occurred only after 2017. The outbreaks of these diseases have been rising because of a lack of adequate sanitation, poor hygiene, and the absence of proper disposal systems. Despite various efforts by the government such as awareness campaigns, guidance on diet for infected individuals, and sanitation improvement programs, the situation is still grim. Disease hotspots and risk factors must be identified, water, sanitation, and hygiene (WASH) services must be improved, and ongoing policies must be effectively implemented to improve the situation. The efforts must be customized to the local environment. In addition, the possible effects of climate change must be projected, and strategies must be accordingly optimized.

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.

Flagella-related gene mutations in Vibrio cholerae during extended cultivation in nutrient-limited media impair cell motility and prolong culturability

IMPORTANCE

Vibrio cholerae undergoes a transition to a viable but non-culturable (VNC) state when subjected to various environmental stresses. We showed here that flagellar motility was involved in the development of the VNC state of V. cholerae. In this study, motility-defective isolates with mutations in various flagella-related genes, but not motile isolates, were predominantly obtained under the stress of long-term batch culture. Other genomic regions were highly conserved, suggesting that the mutations were selective. During the stationary phase of long-term culture, V. cholerae isolates with mutations in the acetate kinase and flagella-related genes were predominant. This study suggests that genes involved in specific functions in V. cholerae undergo mutations under certain environmental conditions.

Rich dynamics of a bidirectionally linked immuno-epidemiological model for cholera

Cholera is an environmentally driven disease where the human hosts both ingest the pathogen from polluted environment and shed the pathogen to the environment, generating a two-way feedback cycle. In this paper, we propose a bidirectionally linked immuno-epidemiological model to study the interaction of within- and between-host cholera dynamics. We conduct a rigorous analysis for this multiscale model, with a focus on the stability and bifurcation properties of each feasible equilibrium. We find that the parameter that represents the bidirectional connection is a key factor in shaping the rich dynamics of the system, including the occurrence of the backward bifurcation and Hopf bifurcation. Numerical results illustrate a practical application of our model and add new insight into the prevention and intervention of cholera epidemics.

Genomic associations with antibody response to an oral cholera vaccine

Oral cholera vaccine is one of the key interventions used in our fight to end the longest pandemic of our time, cholera. The immune response conferred by the currently available cholera vaccines, as measured by serum antibody levels, is variable amongst its recipients. We undertook a genome wide association study (GWAS) on antibody response to the cholera vaccine; globally, the first GWAS on cholera vaccine response. We identified three clusters of bi-allelic SNPs, in high within-cluster linkage disequilibrium that were moderately (p < 5 × 10-6) associated with antibody response to the cholera vaccine and mapped to chromosomal regions 4p14, 4p16.1 and 6q23.3. Intronic SNPs of TBC1D1 comprised the cluster on 4p14, intronic SNPs of TBC1D14 comprised that on 4p16.1 and SNPs upstream of TNFAIP3 formed the cluster on 6q23.3. SNPs within and around these clusters have been implicated in immune cell function and immunological aspects of autoimmune or infectious diseases (e.g., diseases caused by Helicobacter pylori and malarial parasite). 6q23.3 is a prominent region harbouring many loci associated with immune related diseases, including multiple sclerosis, rheumatoid arthritis and systemic lupus erythematosus, as well as IL2 and INFα response to a smallpox vaccine. The gene clusters identified in this study play roles in vesicle-mediated pathway, autophagy and NF-κB signaling. No significant effect of O blood group on antibody response to the cholera vaccine was observed in this study.

Dynamics and profiles of a degenerated reaction-diffusion host-pathogen model with apparent and inapparent infection period

Inapparent infection plays an important role in the disease spread, which is an infection by a pathogen that causes few or no signs or symptoms of infection in the host. Many pathogens, including HIV, typhoid fever, and coronaviruses such as COVID-19 spread in their host populations through inapparent infection. In this paper, we formulated a degenerated reaction-diffusion host-pathogen model with multiple infection period. We split the infectious individuals into two distinct classes: apparent infectious individuals and inapparent infectious individuals, coming from exposed individuals with a ratio of (1-p) and p, respectively. Some preliminary results and threshold-type results are achieved by detailed mathematical analysis. We also investigate the asymptotic profiles of the positive steady state (PSS) when the diffusion rate of susceptible individuals approaches zero or infinity. When all parameters are all constants, the global attractivity of the constant endemic equilibrium is established. It is verified by numerical simulations that spatial heterogeneity of the transmission rates can enhance the intensity of an epidemic. Especially, the transmission rate of inapparent infectious individuals significantly increases the risk of disease transmission, compared to that of apparent infectious individuals and pathogens in the environment, and we should pay special attentions to how to regulate the inapparent infectious individuals for disease control and prevention, which is consistent with the result on the sensitive analysis to the transmission rates through the normalized forward sensitivity index. We also find that disinfection of the infected environment is an important way to prevent and eliminate the risk of environmental transmission.

Nano-Biotechnology for Bacteria Identification and Potent Anti-bacterial Properties: A Review of Current State of the Art

Sepsis is a critical disease caused by the abrupt increase of bacteria in human blood, which subsequently causes a cytokine storm. Early identification of bacteria is critical to treating a patient with proper antibiotics to avoid sepsis. However, conventional culture-based identification takes a long time. Polymerase chain reaction (PCR) is not so successful because of the complexity and similarity in the genome sequence of some bacterial species, making it difficult to design primers and thus less suitable for rapid bacterial identification. To address these issues, several new technologies have been developed. Recent advances in nanotechnology have shown great potential for fast and accurate bacterial identification. The most promising strategy in nanotechnology involves the use of nanoparticles, which has led to the advancement of highly specific and sensitive biosensors capable of detecting and identifying bacteria even at low concentrations in very little time. The primary drawback of conventional antibiotics is the potential for antimicrobial resistance, which can lead to the development of superbacteria, making them difficult to treat. The incorporation of diverse nanomaterials and designs of nanomaterials has been utilized to kill bacteria efficiently. Nanomaterials with distinct physicochemical properties, such as optical and magnetic properties, including plasmonic and magnetic nanoparticles, have been extensively studied for their potential to efficiently kill bacteria. In this review, we are emphasizing the recent advances in nano-biotechnologies for bacterial identification and anti-bacterial properties. The basic principles of new technologies, as well as their future challenges, have been discussed.

Seasonality of cholera in Kolkata and the influence of climate

BACKGROUND

Cholera in Kolkata remains endemic and the Indian city is burdened with a high number of annual cases. Climate change is widely considered to exacerbate cholera, however the precise relationship between climate and cholera is highly heterogeneous in space and considerable variation can be observed even within the Indian subcontinent. To date, relatively few studies have been conducted regarding the influence of climate on cholera in Kolkata.

METHODS

We considered 21 years of confirmed cholera cases from the Infectious Disease Hospital in Kolkata during the period of 1999-2019. We used Generalised Additive Modelling (GAM) to extract the non-linear relationship between cholera and different climatic factors; temperature, rainfall and sea surface temperature (SST). Peak associated lag times were identified using cross-correlation lag analysis.

RESULTS

Our findings revealed a bi-annual pattern of cholera cases with two peaks coinciding with the increase in temperature in summer and the onset of monsoon rains. Variables selected as explanatory variables in the GAM model were temperature and rainfall. Temperature was the only significant factor associated with summer cholera (mean temperature of 30.3 °C associated with RR of 3.8) while rainfall was found to be the main driver of monsoon cholera (550 mm total monthly rainfall associated with RR of 3.38). Lag time analysis revealed that the association between temperature and cholera cases in the summer had a longer peak lag time compared to that between rainfall and cholera during the monsoon. We propose several mechanisms by which these relationships are mediated.

CONCLUSIONS

Kolkata exhibits a dual-peak phenomenon with independent mediating factors. We suggest that the summer peak is due to increased bacterial concentration in urban water bodies, while the monsoon peak is driven by contaminated flood waters. Our results underscore the potential utility of preventative strategies tailored to these seasonal and climatic patterns, including efforts to reduce direct contact with urban water bodies in summer and to protect residents from flood waters during monsoon.

Phylogenetic investigation of Gammaproteobacteria proteins involved in exogenous long-chain fatty acid acquisition and assimilation

Background

The incorporation of exogenous fatty acids into the cell membrane yields structural modifications that directly influence membrane phospholipid composition and indirectly contribute to virulence. FadL and FadD are responsible for importing and activating exogenous fatty acids, while acyltransferases (PlsB, PlsC, PlsX, PlsY) incorporate fatty acids into the cell membrane. Many Gammaproteobacteria species possess multiple homologs of these proteins involved in exogenous fatty acid metabolism, suggesting the evolutionary acquisition and maintenance of this transport pathway.

Methods

This study developed phylogenetic trees based on amino acid and nucleotide sequences of homologs of FadL, FadD, PlsB, PlsC, PlsX, and PlsY via Mr. Bayes and RAxML algorithms. We also explored the operon arrangement of genes encoding for FadL. Additionally, FadL homologs were modeled via SWISS-MODEL, validated and refined by SAVES, Galaxy Refine, and GROMACS, and docked with fatty acids via AutoDock Vina. Resulting affinities were analyzed by 2-way ANOVA test and Tukey's post-hoc test.

Results

Our phylogenetic trees revealed grouping based on operon structure, original homolog blasted from, and order of the homolog, suggesting a more ancestral origin of the multiple homolog phenomena. Our molecular docking simulations indicated a similar binding pattern for the fatty acids between the different FadL homologs.

General significance

Our study is the first to illustrate the phylogeny of these proteins and to investigate the binding of various FadL homologs across orders with fatty acids. This study helps unravel the mystery surrounding these proteins and presents topics for future research.

Cholera outbreak in 2022 among children in Karachi: Study of cases attending to a Tertiary Care Hospital

Objective & Background

Repeated outbreaks of cholera have occurred in Karachi. Changing patterns in seasonality, serotypes and antibiotic resistance have been observed in these outbreaks. Recently, in the year 2022, a surge of cholera cases has been reported from Karachi during the months of April-June. This study aimed to identify clinical features, antibiotic susceptibility, complications, and response to treatment of V. cholerae infection among children attending Indus hospital, Karachi.

Methods

A retrospective chart review of pediatric patients was conducted for children aged 0-16 years. All children treated for culture-proven cholera infection at Indus Hospital from March to June 2022 were included. Details of clinical features, complications, antibiotic susceptibility, and response to treatment were retrieved from the health management information system (HMIS) of the hospital.

Results

Twenty children were included. The median age was 01 (0.50-3.75) years. There were 9 (45%) males and 11 (55%) females. All the culture isolates belonged to serogroup O1 Ogawa of the Vibrio cholerae. Vomiting and diarrhea were the most common symptoms. Dehydration, acute kidney injury, and shock were seen in 19 (95%), 6 (30%), and 2 (10%) children respectively. Eleven children were admitted with an average hospital stay of 5 (Median-IQR 3-6) days. The isolates were completely susceptible to tetracycline, ciprofloxacin, and azithromycin. Different antibiotics were given which included cefotaxime, ceftriaxone, doxycycline, and ciprofloxacin. All children responded completely to the antibiotics.

Conclusion

In present study all V. cholerae isolates belonged to the O1 Ogawa serotype that showed complete susceptibility to tetracycline, ciprofloxacin, and azithromycin. Dehydration, electrolyte imbalance, and renal impairment were the most common complications observed. Drinking unboiled water was identified as a potential source of cholera in most children. Therefore, advocacy of hygienic practices and disinfection of water supplies is recommended to prevent future cholera outbreaks.

Biofilm-a Syntrophic Consortia of Microbial Cells: Boon or Bane?

Biofilm is the conglomeration of microbial cells which is associated with a surface. In the recent times, the study of biofilm has gained popularity and vivid research is being done to know about the effects of biofilm and that it consists of many organisms which are symbiotic in nature, some of which are human pathogens. Here, in this study, we have discussed about biofilms, its formation, relevance of its presence in the biosphere, and the possible remediations to cope up with its negative effects. Since removal of biofilm is difficult, emphasis has been made to suggest ways to prevent biofilm formation and also to devise ways to utilize biofilm in an economically and environment-friendly method.

An immuno-epidemiological model linking between-host and within-host dynamics of cholera

Cholera, a severe gastrointestinal infection caused by the bacterium Vibrio cholerae, remains a major threat to public health, with a yearly estimated global burden of 2.9 million cases. Although most existing models for the disease focus on its population dynamics, the disease evolves from within-host processes to the population, making it imperative to link the multiple scales of the disease to gain better perspectives on its spread and control. In this study, we propose an immuno-epidemiological model that links the between-host and within-host dynamics of cholera. The immunological (within-host) model depicts the interaction of the cholera pathogen with the adaptive immune response. We distinguish pathogen dynamics from immune response dynamics by assigning different time scales. Through a time-scale analysis, we characterise a single infected person by their immune response. Contrary to other within-host models, this modelling approach allows for recovery through pathogen clearance after a finite time. Then, we scale up the dynamics of the infected person to construct an epidemic model, where the infected population is structured by individual immunological dynamics. We derive the basic reproduction number ($ \mathcal{R}_0 $) and analyse the stability of the equilibrium points. At the disease-free equilibrium, the disease will either be eradicated if $ \mathcal{R}_0 < 1 $ or otherwise persists. A unique endemic equilibrium exists when $ \mathcal{R}_0 > 1 $ and is locally asymptotically stable without a loss of immunity.

Estimating the gap between clinical cholera and true community infections: findings from an integrated surveillance study in an endemic region of Bangladesh

Our understanding of cholera transmission and burden largely rely on clinic-based surveillance, which can obscure trends, bias burden estimates and limit the impact of targeted cholera-prevention measures. Serologic surveillance provides a complementary approach to monitoring infections, though the link between serologically-derived infections and medically-attended disease - shaped by immunological, behavioral, and clinical factors - remains poorly understood. We unravel this cascade in a cholera-endemic Bangladeshi community by integrating clinic-based surveillance, healthcare seeking, and longitudinal serological data through statistical modeling. We found >50% of the study population had a V. cholerae O1 infection annually, and infection timing was not consistently correlated with reported cases. Four in 2,340 infections resulted in symptoms, only one of which was reported through the surveillance system. These results provide new insights into cholera transmission dynamics and burden in the epicenter of the 7th cholera pandemic and provide a framework to synthesize serological and clinical surveillance data.

A meta-analysis on the distribution of pathogenic Vibrio species in water sources and wastewater in Africa

Vibrio species are waterborne ubiquitous organisms capable of causing diseases in humans and animals and the occurrence of infections caused by pathogenic Vibrio species among humans have increased globally. This reemergence is attributed to environmental impacts such as global warming and pollution. Africa is most vulnerable to waterborne infections caused by these pathogens because of lack of good water stewardship and management. This study was carried out to provide an in-depth inquiry into the occurrence of pathogenic Vibrio species in water sources and wastewater across Africa. In this regard, a systematic review and meta-analysis was conducted by searching five databases: PubMed, ScienceDirect, Google Scholar, Springer Search and African Journals Online (AJOL). The search yielded 70 articles on pathogenic Vibrio species presence in African aquatic environments that fit our inclusion criteria. Based on the random effects model, the pooled prevalence of pathogenic Vibrio species in various water sources in Africa was 37.6 % (95 % CI: 27.7-48.0). Eighteen countries were represented by the systematically assessed studies and their nationwide prevalence in descending order was: Nigeria (79.82 %), Egypt (47.5 %), Tanzania (45.8 %), Morocco (44.8), South Africa (40.6 %), Uganda (32.1 %), Cameroon (24.5 %), Burkina Faso (18.9 %) and Ghana (5.9 %). Furthermore, 8 pathogenic Vibrio species were identified across water bodies in Africa with the highest detection for V. cholerae (59.5 %), followed by V. parahaemolyticus (10.4 %), V.alginolyticus (9.8 %), V. vulnificus (8.5 %), V. fluvialis (6.6 %), V. mimicus (4.6 %), V. harveyi (0.5 %) and V. metschnikovii (0.1 %). Evidently, pathogenic Vibrio species occurrence in these water sources especially freshwater corroborates the continuous outbreaks observed in Africa. Therefore, there is an urgent need for proactive measures and continuous monitoring of water sources used for various purposes across Africa and proper treatment of wastewater before discharge into water bodies.

Vibrio cholerae Invasion Dynamics of the Chironomid Host Are Strongly Influenced by Aquatic Cell Density and Can Vary by Strain

Cholera has been a human scourge since the early 1800s and remains a global public health challenge, caused by the toxigenic strains of the bacterium Vibrio cholerae. In its aquatic reservoirs, V. cholerae has been shown to live in association with various arthropod hosts, including the chironomids, a diverse insect family commonly found in wet and semiwet habitats. The association between V. cholerae and chironomids may shield the bacterium from environmental stressors and amplify its dissemination. However, the interaction dynamics between V. cholerae and chironomids remain largely unknown.  In this study, we developed freshwater microcosms with chironomid larvae to test the effects of cell density and strain on V. cholerae-chironomid interactions. Our results show that chironomid larvae can be exposed to V. cholerae up to a high inoculation dose (109 cells/mL) without observable detrimental effects. Meanwhile, interstrain variability in host invasion, including prevalence, bacterial load, and effects on host survival, was highly cell density-dependent. Microbiome analysis of the chironomid samples by 16S rRNA gene amplicon sequencing revealed a general effect of V. cholerae exposure on microbiome species evenness. Taken together, our results provide novel insights into V. cholerae invasion dynamics of the chironomid larvae with respect to various doses and strains. The findings suggest that aquatic cell density is a crucial driver of V. cholerae invasion success in chironomid larvae and pave the way for future work examining the effects of a broader dose range and environmental variables (e.g., temperature) on V. cholerae-chironomid interactions. IMPORTANCE Vibrio cholerae is the causative agent of cholera, a significant diarrheal disease affecting millions of people worldwide. Increasing evidence suggests that the environmental facets of the V. cholerae life cycle involve symbiotic associations with aquatic arthropods, which may facilitate its environmental persistence and dissemination. However, the dynamics of interactions between V. cholerae and aquatic arthropods remain unexplored. This study capitalized on using freshwater microcosms with chironomid larvae to investigate the effects of bacterial cell density and strain on V. cholerae-chironomid interactions. Our results suggest that aquatic cell density is the primary determinant of V. cholerae invasion success in chironomid larvae, while interstrain variability in invasion outcomes can be observed under specific cell density conditions. We also determined that V. cholerae exposure generally reduces species evenness of the chironomid-associated microbiome. Collectively, these findings provide novel insights into V. cholerae-arthropod interactions using a newly developed experimental host system.

Model-Based Estimation of Expected Time to Cholera Extinction in Lusaka, Zambia

The developing world has been facing a significant health issue due to cholera as an endemic communicable disease. Lusaka was Zambia's worst affected province, with 5414 reported cases of cholera during the outbreak from late October 2017 to May 12, 2018. To explore the epidemiological characteristics associated with the outbreak, we fitted weekly reported cholera cases with a compartmental disease model that incorporates two transmission routes, namely environment-to-human and human-to-human. Estimates of the basic reproduction number show that both transmission modes contributed almost equally during the first wave. In contrast, the environment-to-human transmission appears to be mostly dominating factor for the second wave. Our study finds that a massive abundance of environmental vibrio's with a huge reduction in water sanitation efficacy triggered the secondary wave. To estimate the expected time to extinction (ETE) of cholera, we formulate the stochastic version of our model and find that cholera can last up to 6.5-7 years in Lusaka if any further outbreak occurs at a later time. Results indicate that a considerable amount of attention is to be paid to sanitation and vaccination programs in order to reduce the severity of the disease and to eradicate cholera from the community in Lusaka.

Coral Disease and Ingestion: Investigating the Role of Heterotrophy in the Transmission of Pathogenic Vibrio spp. using a Sea Anemone (Exaiptasia pallida) Model System

Understanding disease transmission in corals can be complicated given the intricacy of the holobiont and difficulties associated with ex situ coral cultivation. As a result, most of the established transmission pathways for coral disease are associated with perturbance (i.e., damage) rather than evasion of immune defenses. Here, we investigate ingestion as a potential pathway for the transmission of coral pathogens that evades the mucus membrane. Using sea anemones (Exaiptasia pallida) and brine shrimp (Artemia sp.) to model coral feeding, we tracked the acquisition of the putative pathogens, Vibrio alginolyticus, V. harveyi, and V. mediterranei using GFP-tagged strains. Vibrio sp. were provided to anemones using 3 experimental exposures (i) direct water exposure alone, (ii) water exposure in the presence of a food source (non-spiked Artemia), and (iii) through a "spiked" food source (Vibrio-colonized Artemia) created by exposing Artemia cultures to GFP-Vibrio via the ambient water overnight. Following a 3 h feeding/exposure duration, the level of acquired GFP-Vibrio was quantified from anemone tissue homogenate. Ingestion of spiked Artemia resulted in a significantly greater burden of GFP-Vibrio equating to an 830-fold, 3,108-fold, and 435-fold increase in CFU mL^-1 when compared to water exposed trials and a 207-fold, 62-fold, and 27-fold increase in CFU mL^-1 compared to water exposed with food trials for V. alginolyticus, V. harveyi, and V. mediterranei, respectively. These data suggest that ingestion can facilitate delivery of an elevated dose of pathogenic bacteria in cnidarians and may describe an important portal of entry for pathogens in the absence of perturbing conditions. IMPORTANCE The front line of pathogen defense in corals is the mucus membrane. This membrane coats the surface body wall creating a semi-impermeable layer that inhibits pathogen entry from the ambient water both physically and biologically through mutualistic antagonism from resident mucus microbes. To date, much of the coral disease transmission research has been focused on mechanisms associated with perturbance of this membrane such as direct contact, vector lesions (predation/biting), and waterborne exposure through preexisting lesions. The present research describes a potential transmission pathway that evades the defenses provided by this membrane allowing unencumbered entry of bacteria as in association with food. This pathway may explain an important portal of entry for emergence of idiopathic infections in otherwise healthy corals and can be used to improve management practices for coral conservation.

Vibrio cholerae, classification, pathogenesis, immune response, and trends in vaccine development

Vibrio cholerae is the causative agent of cholera, a highly contagious diarrheal disease affecting millions worldwide each year. Cholera is a major public health problem, primarily in countries with poor sanitary conditions and regions affected by natural disasters, where access to safe drinking water is limited. In this narrative review, we aim to summarize the current understanding of the evolution of virulence and pathogenesis of V. cholerae as well as provide an overview of the immune response against this pathogen. We highlight that V. cholerae has a remarkable ability to adapt and evolve, which is a global concern because it increases the risk of cholera outbreaks and the spread of the disease to new regions, making its control even more challenging. Furthermore, we show that this pathogen expresses several virulence factors enabling it to efficiently colonize the human intestine and cause cholera. A cumulative body of work also shows that V. cholerae infection triggers an inflammatory response that influences the development of immune memory against cholera. Lastly, we reviewed the status of licensed cholera vaccines, those undergoing clinical evaluation, and recent progress in developing next-generation vaccines. This review offers a comprehensive view of V. cholerae and identifies knowledge gaps that must be addressed to develop more effective cholera vaccines.

Food as a Driver of a Cholera Epidemic in Jijiga, Ethiopia-June 2017

We conducted a case-control study to identify risk and protective factors during a cholera outbreak in Jijiga, Ethiopia, in June 2017. A case-patient was defined as anyone > 5 years old with at least three loose stools in 24 hours who was admitted to a cholera treatment center in Jijiga on or after June 16, 2017. Two controls were matched to each case by type of residency (rural or urban) and age group. We enrolled 55 case-patients and 102 controls from June 16 to June 23, 2017. Identified risk factors for cholera were male sex, eating cold food, and eating food outside the home. Eating hot food was protective, as was reported handwashing after defecation; no other reported water, sanitation, and hygiene factors were associated with cholera risk. Recommendations included continuing messaging about safe food handling practices at home, the dangers of consuming meals prepared away from home, and the importance of hand hygiene practices.

Cyanobacterial Harmful Algal Bloom Toxin Microcystin and Increased Vibrio Occurrence as Climate-Change-Induced Biological Co-Stressors: Exposure and Disease Outcomes via Their Interaction with Gut-Liver-Brain Axis

The effects of global warming are not limited to rising global temperatures and have set in motion a complex chain of events contributing to climate change. A consequence of global warming and the resultant climate change is the rise in cyanobacterial harmful algal blooms (cyano-HABs) across the world, which pose a threat to public health, aquatic biodiversity, and the livelihood of communities that depend on these water systems, such as farmers and fishers. An increase in cyano-HABs and their intensity is associated with an increase in the leakage of cyanotoxins. Microcystins (MCs) are hepatotoxins produced by some cyanobacterial species, and their organ toxicology has been extensively studied. Recent mouse studies suggest that MCs can induce gut resistome changes. Opportunistic pathogens such as Vibrios are abundantly found in the same habitat as phytoplankton, such as cyanobacteria. Further, MCs can complicate human disorders such as heat stress, cardiovascular diseases, type II diabetes, and non-alcoholic fatty liver disease. Firstly, this review describes how climate change mediates the rise in cyanobacterial harmful algal blooms in freshwater, causing increased levels of MCs. In the later sections, we aim to untangle the ways in which MCs can impact various public health concerns, either solely or in combination with other factors resulting from climate change. In conclusion, this review helps researchers understand the multiple challenges brought forth by a changing climate and the complex relationships between microcystin, Vibrios, and various environmental factors and their effect on human health and disease.

Vibrio cholerae biofilms use modular adhesins with glycan-targeting and nonspecific surface binding domains for colonization

Bacterial biofilms are formed on environmental surfaces and host tissues, and facilitate host colonization and antibiotic resistance by human pathogens. Bacteria often express multiple adhesive proteins (adhesins), but it is often unclear whether adhesins have specialized or redundant roles. Here, we show how the model biofilm-forming organism Vibrio cholerae uses two adhesins with overlapping but distinct functions to achieve robust adhesion to diverse surfaces. Both biofilm-specific adhesins Bap1 and RbmC function as a "double-sided tape": they share a β-propeller domain that binds to the biofilm matrix exopolysaccharide, but have distinct environment-facing domains. Bap1 adheres to lipids and abiotic surfaces, while RbmC mainly mediates binding to host surfaces. Furthermore, both adhesins contribute to adhesion in an enteroid monolayer colonization model. We expect that similar modular domains may be utilized by other pathogens, and this line of research can potentially lead to new biofilm-removal strategies and biofilm-inspired adhesives.

Gut commensal Enterocloster species host inoviruses that are secreted in vitro and in vivo

BACKGROUND

Bacteriophages in the family Inoviridae, or inoviruses, are under-characterized phages previously implicated in bacterial pathogenesis by contributing to biofilm formation, immune evasion, and toxin secretion. Unlike most bacteriophages, inoviruses do not lyse their host cells to release new progeny virions; rather, they encode a secretion system that actively pumps them out of the bacterial cell. To date, no inovirus associated with the human gut microbiome has been isolated or characterized.

RESULTS

In this study, we utilized in silico, in vitro, and in vivo methods to detect inoviruses in bacterial members of the gut microbiota. By screening a representative genome library of gut commensals, we detected inovirus prophages in Enterocloster spp. (formerly Clostridium spp.). We confirmed the secretion of inovirus particles in in vitro cultures of these organisms using imaging and qPCR. To assess how the gut abiotic environment, bacterial physiology, and inovirus secretion may be linked, we deployed a tripartite in vitro assay that progressively evaluated bacterial growth dynamics, biofilm formation, and inovirus secretion in the presence of changing osmotic environments. Counter to other inovirus-producing bacteria, inovirus production was not correlated with biofilm formation in Enterocloster spp. Instead, the Enterocloster strains had heterogeneous responses to changing osmolality levels relevant to gut physiology. Notably, increasing osmolality induced inovirus secretion in a strain-dependent manner. We confirmed inovirus secretion in a gnotobiotic mouse model inoculated with individual Enterocloster strains in vivo in unperturbed conditions. Furthermore, consistent with our in vitro observations, inovirus secretion was regulated by a changed osmotic environment in the gut due to osmotic laxatives.

CONCLUSION

In this study, we report on the detection and characterization of novel inoviruses from gut commensals in the Enterocloster genus. Together, our results demonstrate that human gut-associated bacteria can secrete inoviruses and begin to elucidate the environmental niche filled by inoviruses in commensal bacteria. Video Abstract.

Computational approaches screening DNA aptamers against conserved outer membrane protein W of Vibrio cholerae O1- an investigation expanding the potential for point-of-care detection with aptasensors

Foodborne outbreaks urge public health domain to upgrade diagnosis by means of simpler, quicker, and more affordable pathogen detection methods. A molecular recognition probe against an analyte of interest makes up a biosensor, along with a method for turning the recognition event into a quantifiable signal. Single-stranded DNA or RNA aptamers are promising bio-recognition molecules for a range of targets, including a wide range of non-nucleic acid targets with which they are highly specific and affine. In the proposed study, 40 DNA aptamers were screened and analyzed interactions using in-silico SELEX procedures, which can selectively interact with active sites at the extracellular region of the Outer membrane Protein W (OmpW) of Vibrio Cholerae. Multiple modeling techniques, like protein structural prediction with I-TASSER, aptamer structural modeling using M-fold, RNA composer, protein-DNA docking using HADDOCK, and large-scale (500 ns) molecular dynamics simulations through GROMACS have been employed. Out of 40, six aptamers having lowest free energy were docked against the predicted active site at the extracellular region of OmpW. VBAPT4-OmpW and VBAPT17-OmpW, the two highest-scoring Aptamer-Protein complexes, were chosen for molecular dynamics simulations. VBAPT4-OmpW is quite unable to attain its structural local minima after 500 ns. But VBAPT17-OmpW is showing great stability and is not destructive even after 500 ns. RMSF, DSSP, PCA, and Essential Dynamics all provided additional confirmation. Current findings, combined with the fabrication of biosensor devices, could pave the way for an innovative pathogen detection platform with high sensitivity, along with an effective and low-impact curative strategy for corresponding diseases.Communicated by Ramaswamy H. Sarma.

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.

A Well-Posed Fractional Order Cholera Model with Saturated Incidence Rate

A fractional-order cholera model in the Caputo sense is constructed. The model is an extension of the Susceptible-Infected-Recovered (SIR) epidemic model. The transmission dynamics of the disease are studied by incorporating the saturated incidence rate into the model. This is particularly important since assuming that the increase in incidence for a large number of infected individualsis equivalent to a small number of infected individualsdoes not make much sense. The positivity, boundedness, existence, and uniqueness of the solution of the model are also studied. Equilibrium solutions are computed, and their stability analyses are shown to depend on a threshold quantity, the basic reproduction ratio (R0). It is clearly shown that if R0<1, the disease-free equilibrium is locally asymptotically stable, whereas if R0>1, the endemic equilibrium exists and is locally asymptotically stable. Numerical simulations are carried out to support the analytic results and to show the significance of the fractional order from the biological point of view. Furthermore, the significance of awareness is studied in the numerical section.

A simple mechanism for integration of quorum sensing and cAMP signalling in V. cholerae

Many bacteria use quorum sensing to control changes in lifestyle. The process is regulated by microbially derived "autoinducer" signalling molecules, that accumulate in the local environment. Individual cells sense autoinducer abundance, to infer population density, and alter their behaviour accordingly. In Vibrio cholerae , quorum sensing signals are transduced by phosphorelay to the transcription factor LuxO. Unphosphorylated LuxO permits expression of HapR, which alters global gene expression patterns. In this work, we have mapped the genome-wide distribution of LuxO and HapR in V. cholerae . Whilst LuxO has a small regulon, HapR targets 32 loci. Many HapR targets coincide with sites for the cAMP receptor protein (CRP) that regulates the transcriptional response to carbon starvation. This overlap, also evident in other Vibrio species, results from similarities in the DNA sequence bound by each factor. At shared sites, HapR and CRP simultaneously contact the double helix and binding is stabilised by direct interaction of the two factors. Importantly, this involves a CRP surface that usually contacts RNA polymerase to stimulate transcription. As a result, HapR can block transcription activation by CRP. Thus, by interacting at shared sites, HapR and CRP integrate information from quorum sensing and cAMP signalling to control gene expression.

In silico prediction of molecular mechanisms of toxicity mediated by the leptospiral PF07598 gene family-encoded virulence-modifying proteins

Mechanisms of leptospirosis pathogenesis remain unclear despite the identification of a number of potential leptospiral virulence factors. We recently demonstrated potential mechanisms by which the virulence-modifying (VM) proteins-defined as containing a Domain of Unknown function (DUF1561), encoded by the PF07598 gene family-found only in group 1 pathogenic Leptospira-might mediate the clinical pathogenesis of leptospirosis. VM proteins belongs to classical AB toxin paradigm though have a unique AB domain architecture, unlike other AB toxins such as diphtheria toxin, pertussis toxin, shiga toxin, or ricin toxin which are typically encoded by two or more genes and self-assembled into a multi-domain holotoxin. Leptospiral VM proteins are secreted R-type lectin domain-containing exotoxins with discrete N-terminal ricin B-like domains involved in host cell surface binding, and a C-terminal DNase/toxin domain. Here we use the artificial intelligence-based AlphaFold algorithm and other computational tools to predict and elaborate on details of the VM protein structure-function relationship. Comparative AlphaFold and CD-spectroscopy defined the consistent secondary structure (Helix and ß-sheet) content, and the stability of the functional domains were further supported by molecular dynamics simulation. VM proteins comprises distinctive lectic family (QxW)₃ motifs, the Mycoplasma CARDS toxin (D3 domain, aromatic patches), C-terminal similarity with mammalian DNase I. In-silico study proposed that Gln412, Gln523, His533, Thr59 are the high binding energy or ligand binding residues plausibly anticipates in the functional activities. Divalent cation (Mg⁺²-Gln412) and phosphate ion (PO₄]^-3-Arg615) interaction further supports the functional activities driven by C-terminal domain. Computation-driven structure-function studies of VM proteins will guide experimentation towards mechanistic understandings of leptospirosis pathogenesis, which underlie development of new therapeutic and preventive measures for this devastating disease.

Knowledge, Attitude, and Practice in a Sample of the Lebanese Population Regarding Cholera

The evaluation of knowledge, attitude, and practices towards an emerging disease is an essential component of public health preventive measures during an outbreak. In October 2022, an outbreak of cholera was reported in Lebanon, which is the first to be reported in the Middle Eastern country for 30 years. This study aimed to explore the level of knowledge as well as attitude and practice of the general public in Lebanon towards cholera. A self-administered structured questionnaire was distributed via an online link to individuals living in Lebanon during October-November 2022. The survey instrument comprised items to assess the sociodemographic data; questions on knowledge about cholera symptoms, transmission, and prevention; as well as attitude and practice questions. Our study involved 553 participants, with a median age of 24 years and a majority of females (72.5%). The results showed that the majority of respondents correctly identified diarrhea as a symptom of cholera and recognized the spread via contaminated water and food. Having a university level education compared with secondary school or less (adjusted odds ratio (aOR) = 2.09), being married compared with single (aOR = 1.67), and working in the medical field compared with unemployed (aOR = 4.19) were significantly associated with higher odds of having good cholera knowledge. Having good knowledge compared with having a poor level of cholera knowledge (aOR = 1.83) and older age (aOR = 1.03) were significantly associated with higher odds of having a good attitude towards cholera. The current study showed an overall high knowledge score on cholera among the Lebanese population. Nevertheless, gaps in cholera knowledge were identified and should be addressed, particularly among workers in the medical field. Thus, we recommend targeted health education to the general population that aims to strengthen the health resilience in the community.

Bacteria-bacteriophage cycles facilitate Cholera outbreak cycles: an indirect Susceptible-Infected-Recovered-Bacteria- Phage (iSIRBP) model-based mathematical study

Cholera is an acute enteric infectious disease caused by the Gram-negative bacterium Vibrio cholerae. Despite a huge body of research, the precise nature of its transmission dynamics has yet to be fully elucidated. Mathematical models can be useful to better understand how an infectious agent can spread and be properly controlled. We develop a compartmental model describing a human population, a bacterial population as well as a phage population. We show that there might be eight equilibrium points, one of which is a disease free equilibrium point. We carry out numerical simulations and sensitivity analyses and we show that the presence of phage can reduce the number of infectious individuals. Moreover, we discuss the main implications in terms of public health management and control strategies.

Mathematical Models for Cholera Dynamics-A Review

Cholera remains a significant public health burden in many countries and regions of the world, highlighting the need for a deeper understanding of the mechanisms associated with its transmission, spread, and control. Mathematical modeling offers a valuable research tool to investigate cholera dynamics and explore effective intervention strategies. In this article, we provide a review of the current state in the modeling studies of cholera. Starting from an introduction of basic cholera transmission models and their applications, we survey model extensions in several directions that include spatial and temporal heterogeneities, effects of disease control, impacts of human behavior, and multi-scale infection dynamics. We discuss some challenges and opportunities for future modeling efforts on cholera dynamics, and emphasize the importance of collaborations between different modeling groups and different disciplines in advancing this research area.

A phage weaponizes a satellite recombinase to subvert viral restriction

Bacteria can acquire mobile genetic elements (MGEs) to combat infection by viruses (phages). Satellite viruses, including the PLEs (phage-inducible chromosomal island-like elements) in epidemic Vibrio cholerae, are MGEs that restrict phage replication to the benefit of their host bacterium. PLEs parasitize the lytic phage ICP1, unleashing multiple mechanisms to restrict phage replication and promote their own spread. In the arms race against PLE, ICP1 uses nucleases, including CRISPR-Cas, to destroy PLE's genome during infection. However, through an unknown CRISPR-independent mechanism, specific ICP1 isolates subvert restriction by PLE. Here, we discover ICP1-encoded Adi that counteracts PLE by exploiting the PLE's large serine recombinase (LSR), which normally mobilizes PLE in response to ICP1 infection. Unlike previously characterized ICP1-encoded anti-PLE mechanisms, Adi is not a nuclease itself but instead appears to modulate the activity of the LSR to promote destructive nuclease activity at the LSR's specific attachment site, attP. The PLE LSR, its catalytic activity, and attP are additionally sufficient to sensitize a PLE encoding a resistant variant of the recombination module to Adi activity. This work highlights a unique type of adaptation arising from inter-genome conflicts, in which the intended activity of a protein can be weaponized to overcome the antagonizing genome.