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. 2021 Nov 18:12:757986.
doi: 10.3389/fmicb.2021.757986. eCollection 2021.

Origin and Dissemination of Altered El Tor Vibrio cholerae O1 Causing Cholera in Odisha, India: Two and Half Decade's View

Bibhuti Bhusan Pal  1 , Dipti Ranjan Behera  1 , Smruti Ranjan Nayak  1 , Ashish Kumar Nayak  1
Affiliations

Origin and Dissemination of Altered El Tor Vibrio cholerae O1 Causing Cholera in Odisha, India: Two and Half Decade's View

Bibhuti Bhusan Pal et al. Front Microbiol. .

Abstract

The origin, spread and molecular epidemiology of altered El Tor Vibrio cholerae O1 strains isolated from cholera outbreaks/surveillance studies between 1995 and 2019 from different district of Odisha were analyzed. The stock cultures of V. cholerae O1 strains from 1995 to 2019 were analyzed through molecular analysis using different PCR assays and pulse field gel electrophoresis (PFGE) analysis. The spread map (month, year and place) was constructed to locate the dissemination of altered El Tor variants of V. cholerae O1 in this region. A total of 13 cholera outbreaks were caused by V. cholerae O1 Ogawa biotype El Tor carrying ctxB1 and ctxB7 genotypes. The ctxB1 alleles of V. cholerae O1 mostly confined to the coastal areas, whereas the ctxB7 genotypes, though originating in the coastal region of Odisha, concentrated more in the tribal areas. The positive correlation between virulence-associated genes (VAGs) was found through Pearson's correlation model, indicative of a stronger association between the VAGs. The clonal relationship through PFGE between ctxB1 and ctxB7 genotypes of V. cholerae O1 strains exhibited 80% similarity indicating single- or multi-clonal evolution. It is evident from this study that the spread of multidrug-resistant V. cholerae O1-altered El Tor was dominant over the prototype El Tor strains in this region. The origin of altered El Tor variants of V. cholerae O1 occurred in the East Coast of Odisha established that the origin of cholera happened in the Gangetic belts of Bay of Bengal where all new variants of V. cholerae O1 might have originated from the Asian countries.

Keywords: Odisha; V. cholerae O1; ctxB1 and ctxB7 genotypes; origin; spread.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer PK declared a shared affiliation with the authors to the handling editor at the time of the review

Figures

FIGURE 1
FIGURE 1
Distribution of cholera cases and outbreaks in Odisha: 1999–2019.
FIGURE 2
FIGURE 2
Dendrogram drawn using PAST 4.03 software. (A) Cluster analysis of the estimate of genetic similarity between ctxB genotypes present in V. cholerae O1 strains in different years. (B) Cluster analysis of the estimate of percentage similarity of virulence-associated genes (VAGs) present in V. cholerae O1 strains in different years.
FIGURE 3
FIGURE 3
(A) Scatter plot of the correlation between virulence genes of Vibrio cholerae O1 strains. The data represent different magnitudes of correlation coefficient (r) ranges between –0.5 and 1.0. A positive correlation indicated a stronger association between the variables and vice versa. The greater the absolute value of the Pearson product–moment correlation coefficient, the stronger the linear relationship. (B) Heat map showing the percentage variation in different virulence-associated genes distributed among the strains in different years.
FIGURE 4
FIGURE 4
Month- and year-wise spread of El Tor variant Vibrio cholerae O1 strains. (A) Spread of ctxB1 (B) spread of ctxB7 genotypes in Odisha: 1995–2019.
FIGURE 5
FIGURE 5
Spread of V. cholerae O1 biotype El Tor in three blocks of Rayagada district (Kashipur, Kalyansinghpur, and Bissam Cuttack): August–September, 2010.
FIGURE 6
FIGURE 6
PFGE patterns of the NotI-digested Vibrio cholerae O1 strains isolated from different districts of Odisha: 1995–2019. Capital letters means different clusters.
See this image and copyright information in PMC

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