Abstract
Recurrent cholera causes significant morbidity and mortality in cholera endemic estuarine areas of Bangladesh. There have been limited studies to investigate the transmission patterns of V. cholerae associated with cholera in Bangladesh. In this study, we characterized V. cholerae serogroup O1 isolated from 30 cholera patients, 76 household contacts, 119 stored drinking water samples, and 119 water source samples in Bakerganj and Mathbaria, two cholera endemic coastal regions in Bangladesh. Results of phenotypic and molecular characterization of V. cholerae isolates (n = 56) confirmed them to be toxigenic belonging to serogroup O1 biotype El Tor (ET), and possessing cholera toxin of the classical biotype (altered ET). Molecular fingerprinting of the V. cholerae O1 of clinical and water origins determined by PFGE of Not-I- digested genomic DNA showed them to be closely related, as the PFGE banding patterns were highly homogenous. Phylogenetic analysis using dendrogram of cholera patients, household contacts, and household groundwater sources showed isolates within households to be clonally linked, suggesting water as an important vehicle of transmission of cholera in the coastal villages of Bangladesh. Transmission of toxigenic V. cholerae O1 through drinking water in cholera endemic rural settings underscores the urgent need for evidence based water, sanitation, and hygiene interventions promoting safe drinking water to prevent morbidity and mortality related to cholera and other enteric infections in Bangladesh.
Highlights
Cholera is an acute dehydrating, potentially life-threatening diarrheal disease, transmitted through contaminated drinking water and poor WASH infrastructure and practices in low resource settings [1]
We investigate person to person and environmental transmission routes for cholera infection among household contacts of cholera cases using pulsed-field gel electrophoresis (PFGE) of selected V. cholerae O1 isolated from coastal villages of Bangladesh namely Mathbaria and Bakerganj to identify the transmission routes that should be targeted in future interventions
We performed genetic characterization of 56 V. cholerae O1 isolated from 30 cholera patients; 76 household contacts and 238 water samples (119 stored drinking water samples, and 119 water source samples) collected from 30 households
Summary
Cholera is an acute dehydrating, potentially life-threatening diarrheal disease, transmitted through contaminated drinking water and poor WASH infrastructure and practices in low resource settings [1]. Of the more than 200 serogroups of V. cholerae, only serogroups O1 and O139 which possess potent cholera toxin (CT) encoded by a filamentous prophage lysogenizing into the genome of the bacterium are responsible for the epidemic and pandemic cholera worldwide [3]. V. cholerae O1classical biotype caused the sixth and presumably earlier pandemics out of seven cholera pandemics before being replaced with the ET biotype which has been responsible for the ongoing seventh pandemic since 1961 [4, 5]. The El Tor biotype strains have undergone genetic changes such as a new hybrid El Tor carrying the classical biotype CT [6].These El Tor variant strains are referred to as “hyper-virulent” owing to their ability to produce more cholera toxin, greater spreading ability during epidemics, and increased competitive fitness for colonization than many ET isolates [7,8,9]
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