Association of Heavy Rainfall on Genotypic Diversity in V. cholerae Isolates from an Outbreak in India

Non-serogroup O1/O139 agglutinable Vibrio cholerae: a phylogenetically and genealogically neglected yet emerging potential pathogen of clinical relevance

Somatic antigen agglutinable type-1/139 Vibrio cholerae (SAAT-1/139-Vc) members or O1/O139 V. cholerae have been described by various investigators as pathogenic due to their increasing virulence potential and production of choleragen. Reported cholera outbreak cases around the world have been associated with these choleragenic V. cholerae with high case fatality affecting various human and animals. These virulent Vibrio members have shown genealogical and phylogenetic relationship with the avirulent somatic antigen non-agglutinable strains of 1/139 V. cholerae (SANAS-1/139- Vc) or O1/O139 non-agglutinating V. cholerae (O1/O139-NAG-Vc). Reports on implication of O1/O139-NAGVc members in most sporadic cholera/cholera-like cases of diarrhea, production of cholera toxin and transmission via consumption and/or contact with contaminated water/seafood are currently on the rise. Some reported sporadic cases of cholera outbreaks and observed change in nature has also been tracable to these non-agglutinable Vibrio members (O1/O139-NAGVc) yet there is a sustained paucity of research interest on the non-agglutinable V. cholerae members. The emergence of fulminating extraintestinal and systemic vibriosis is another aspect of SANAS-1/139- Vc implication which has received low attention in terms of research driven interest. This review addresses the need to appraise and continually expand research based studies on the somatic antigen non-serogroup agglutinable type-1/139 V.cholerae members which are currently prevalent in studies of water bodies, fruits/vegetables, foods and terrestrial environment. Our opinion is amassed from interest in integrated surveillance studies, management/control of cholera outbreaks as well as diarrhea and other disease-related cases both in the rural, suburban and urban metropolis.

Characterization of V. cholerae O1 biotype El Tor serotype Ogawa possessing the ctxB gene of the classical biotype isolated from well water associated with the cholera outbreak in Kerala, South India

We investigated 22 water samples (17 well water and five pipe water - both chlorinated) and six soil samples from the surroundings of wells of the households of suspected patients from Palakkad district, Kerala (India), from where a cholera outbreak was reported during June-July 2016. A total of 25 Vibrio cholerae isolates were collected from three well water samples during a recent cholera outbreak. Biochemical and serological studies revealed that all of the isolates belonged to serogroup O1, biotype El Tor, serotype Ogawa. PCR assays confirmed the occurrence of ctxB, ctxA, hlyA, tcpA El Tor,VPI, ace, zot, ompW, rfbO1 and toxR genes in all isolates. The presence of the ctxB gene of the classical biotype in all of the El Tor isolates suggests that it is a new variant of El Tor biotype. Antibiogram profile of all V. cholerae O1 isolates revealed resistance towards five classes of antibiotics island and indicates that they were multidrug resistant. ERIC-PCR and PFGE finger prints showed the clonal relationship among the V. cholerae O1 isolates. The results of this study revealed the emergence of a new variant of El Tor biotype in the water samples from Palakkad district, from where a cholera outbreak was reported.

Stemming cholera tides in Zimbabwe through mass vaccination

BACKGROUND

In 2018, Zimbabwe declared another major cholera outbreak a decade after recording one of the worst cholera outbreaks in Africa.

METHODS

A mathematical model for cholera was used to estimate the magnitude of the cholera outbreak and vaccination coverage using cholera cases reported data. A Markov chain Monte Carlo method based on a Bayesian framework was used to fit the model in order to estimate the basic reproductive number and required vaccination coverage for cholera control.

RESULTS

The results showed that the outbreak had a basic reproductive number of 1.82 (95% credible interval [CrI] 1.53-2.11) and required vaccination coverage of at least 58% (95% Crl 45-68%) to be contained using an oral cholera vaccine of 78% efficacy. Sensitivity analysis demonstrated that a vaccine with at least 55% efficacy was sufficient to contain the outbreak but at higher coverage of 75% (95% Crl 58-88%). However, high-efficacy vaccines would greatly reduce the required coverage, with 100% efficacy vaccine reducing coverage to 45% (95% Crl 35-53%).

CONCLUSIONS

These findings reinforce the crucial need for oral cholera vaccines to control cholera in Zimbabwe, considering that the decay of water reticulation and sewerage infrastructure is unlikely to be effectively addressed in the coming years.

The Impact of Climate Change on Cholera: A Review on the Global Status and Future Challenges

Water ecosystems can be rather sensitive to evolving or sudden changes in weather parameters. These changes can result in alterations in the natural habitat of pathogens, vectors, and human hosts, as well as in the transmission dynamics and geographic distribution of infectious agents. However, the interaction between climate change and infectious disease is rather complicated and not deeply understood. In this narrative review, we discuss climate-driven changes in the epidemiology of Vibrio species-associated diseases with an emphasis on cholera. Changes in environmental parameters do shape the epidemiology of Vibrio cholerae. Outbreaks of cholera cause significant disease burden, especially in developing countries. Improved sanitation systems, access to clean water, educational strategies, and vaccination campaigns can help control vibriosis. In addition, real-time assessment of climatic parameters with remote-sensing technologies in combination with robust surveillance systems could help detect environmental changes in high-risk areas and result in early public health interventions that can mitigate potential outbreaks.

Virulence, antimicrobial and heavy metal tolerance, and genetic diversity of Vibrio cholerae recovered from commonly consumed freshwater fish

Vibrio cholerae is a leading waterborne pathogen worldwide. Continuous monitoring of V. cholerae contamination in aquatic products and identification of risk factors are crucial for assuring food safety. In this study, we determined the virulence, antimicrobial susceptibility, heavy metal tolerance, and genetic diversity of 400 V. cholerae isolates recovered from commonly consumed freshwater fish (Aristichthys nobilis, Carassius auratus, Ctenopharyngodon idellus, and Parabramis pekinensis) collected in July and August of 2017 in Shanghai, China. V. cholerae has not been previously detected in the half of these fish species. The results revealed an extremely low occurrence of pathogenic V. cholerae carrying the major virulence genes ctxAB (0.0%), tcpA (0.0%), ace (0.0%), and zot (0.0%). However, high incidence of virulence-associated genes was observed, including the RTX toxin gene cluster (rtxA-D) (83.0-97.0%), hlyA (87.8%), hapA (95.0%), and tlh (76.0%). Meanwhile, high percentages of resistance to antimicrobial agents streptomycin (65.3%), ampicillin (44.5%), and rifampicin (24.0%) were observed. Approximately 30.5% of the isolates displayed multidrug resistant (MDR) phenotypes with 42 resistance profiles, which were significantly different among the four fish species (MARI, P = 0.001). Additionally, tolerance of isolates to heavy metals Hg²⁺ (49.3%), Zn²⁺ (30.3%), and Pb²⁺ (12.0%) was observed. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR)-based fingerprinting of the 400 V. cholerae isolates revealed 328 ERIC-genotypes, which demonstrated a large degree of genomic variation among the isolates. Overall, the results of this study support the need for food safety risk assessment of aquatic products.

Molecular Epidemiology of Cholera Outbreaks during the Rainy Season in Mandalay, Myanmar

Cholera, caused by Vibrio cholerae, remains a global threat to public health. In Myanmar, the availability of published information on the occurrence of the disease is scarce. We report here that cholera incidence in Mandalay generally exhibited a single annual peak, with an annual average of 312 patients with severe dehydration over the past 5 years (since 2011) and was closely associated with the rainy season. We analyzed cholera outbreaks, characterized 67 isolates of V. cholerae serogroup O1 in 2015 from patients from Mandalay, and compared them with 22 V. cholerae O1 isolates (12 from Mandalay and 10 from Yangon) in 2014. The isolates carried the classical cholera toxin B subunit (ctxB), the toxin-coregulated pilus A (tcpA) of Haitian type, and repeat sequence transcriptional regulator (rstR) of El Tor type. Two molecular typing methods, pulsed-field gel electrophoresis and multiple-locus variable-number tandem repeat analysis (MLVA), differentiated the 89 isolates into seven pulsotypes and 15 MLVA profiles. Pulsotype Y15 and one MLVA profile (11, 7, 7, 16, 7) were predominantly found in the isolates from cholera outbreaks in Mandalay, 2015. Pulsotypes Y11, Y12, and Y15 with some MLVA profiles were detected in the isolates from two remote areas, Mandalay and Yangon, with temporal changes. These data suggested that cholera spread from the seaside to the inland area in Myanmar.

Pandemics, pathogenicity and changing molecular epidemiology of cholera in the era of global warming

Background

Vibrio cholerae, a Gram-negative, non-spore forming curved rod is found in diverse aquatic ecosystems around the planet. It is classified according to its major surface antigen into around 206 serogroups, of which O1 and O139 cause epidemic cholera. A recent spatial modelling technique estimated that around 2.86 million cholera cases occur globally every year, and of them approximately 95,000 die. About 1.3 billion people are currently at risk of infection from cholera. Meta-analysis and mathematical modelling have demonstrated that due to global warming the burden of vector-borne diseases like malaria, leishmaniasis, meningococcal meningitis, viral encephalitis, dengue and chikungunya will increase in the coming years in the tropics and beyond.

Cholera and climate

This review offers an overview of the interplay between global warming and the pathogenicity and epidemiology of V. cholerae. Several distinctive features of cholera survival (optimal thriving at 15% salinity, 30 °C water temperature, and pH 8.5) indicate a possible role of climate change in triggering the epidemic process. Genetic exchange (ctxAB, zot, ace, cep, and orfU) between strains and transduction process allows potential emergence of new toxigenic clones. These processes are probably controlled by precise environmental signals such as optimum temperature, sunlight and osmotic conditions. Environmental influences on phytoplankton growth and chitin remineralization will be discussed alongside the interplay of poor sanitary conditions, overcrowding, improper sewage disposal and global warming in promoting the growth and transmission of this deadly disease.

Conclusion

The development of an effective early warning system based on climate data could help to prevent and control future outbreaks. It may become possible to integrate real-time monitoring of oceanic regions, climate variability and epidemiological and demographic population dynamics to predict cholera outbreaks and support the design of cost-effective public health strategies.