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Amplified fragment length polymorphism of clinical and environmental Vibrio cholerae from a freshwater environment in a cholera-endemic area, India

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Title Amplified fragment length polymorphism of
clinical and environmental Vibrio cholerae from a
freshwater environment in a cholera-endemic
area, India
 
Creator Mishra, Arti
Taneja, Neelam
Sharma, R K
Kumar, Rahul
Sharma, Naresh C
Sharma, Meera
 
Subject Plant sciences
Plant Biotechnology
 
Description Abstract
Background: The region around Chandigarh in India has witnessed a resurgence of cholera. However, isolation of
V. cholerae O1 from the environment is infrequent. Therefore, to study whether environmental nonO1-nonO139
isolates, which are native to the aquatic ecosystem, act as precursors for pathogenic O1 strains, their virulence
potential and evolutionary relatedness was checked.
Methods: V. cholerae was isolated from clinical cases of cholera and from water and plankton samples collected
from freshwater bodies and cholera-affected areas. PCR analysis for the ctxA, ctxB, tcpA, toxT and toxR genes and
AFLP with six primer combinations was performed on 52 isolates (13 clinical, 34 environmental and 5 reference
strains).
Results: All clinical and 3 environmental isolates belonged to serogroup O1 and remaining 31 environmental V.
cholerae were nonO1-nonO139. Serogroup O1 isolates were ctxA, tcpA (ElTor), ctxB (Classical), toxR and toxT positive.
NonO1-nonO139 isolates possessed toxR, but lacked ctxA and ctxB; only one isolate was positive for toxT and tcpA.
Using AFLP, 2.08% of the V. cholerae genome was interrogated. Dendrogram analysis showed one large
heterogeneous clade (n = 41), with two compact and distinct subclades (1a and 1b), and six small mono-phyletic
groups. Although V. cholerae O1 isolates formed a distinct compact subclade, they were not clonal. A clinical O1
strain clustered with the nonO1-nonO139 isolates; one strain exhibited 70% similarity to the Classical control strain,
and all O1 strains possessed an ElTor variant-specific fragment identified with primer ECMT. Few nonO1-nonO139
isolates from widely separated geographical locations intermingled together. Three environmental O1 isolates
exhibited similar profiles to clinical O1 isolates.
Conclusion: In a unique study from freshwater environs of a cholera-endemic area in India over a narrow time
frame, environmental V. cholerae population was found to be highly heterogeneous, diverse and devoid of major
virulence genes. O1 and nonO1-nonO139 isolates showed distinct lineages. Clinical isolates were not clonal but
were closely related, indicating accumulation of genetic differences over a short time span. Though, environment
plays an important role in the spread of cholera, the possibility of an origin of pathogenic O1 strains from
environmental nonO1-nonO139 strains seems to be remote in our region.
 
Date 2011
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://ihbt.csircentral.net/1066/1/104_2011_Amplified_fragment.pdf
Mishra, Arti and Taneja, Neelam and Sharma, R K and Kumar, Rahul and Sharma, Naresh C and Sharma, Meera (2011) Amplified fragment length polymorphism of clinical and environmental Vibrio cholerae from a freshwater environment in a cholera-endemic area, India. Mishra et al. BMC Infectious Diseases, 11. pp. 2-9.
 
Relation http://ihbt.csircentral.net/1066/