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

BMC Infectious Diseases

Research Article

Ram K Sharma¹  Rahul Kumar¹  Meera Sharma²  Neelam Taneja²  Arti Mishra²  Naresh C Sharma³ 

[1] Biotechnology Division, Institute of Himalayan Bioresource and Technology, 176061, Palampur, Himachal Pradesh, India;Department of Medical Microbiology, Post Graduate Institute of Medical Education and Research, 160012, Chandigarh, India;Laboratory Department, Maharishi Valmiki Infectious Diseases Hospital, Kingsway Camp, 110009, Delhi, India;

关键词: Amplify Fragment Length Polymorphism;    Cholera;    Microbial Type Culture Collection;    Environmental Isolate;    Amplify Fragment Length Polymorphism Analysis;   

DOI  :  10.1186/1471-2334-11-249

 received in 2011-01-24, accepted in 2011-09-22,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundThe 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.MethodsV. 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).ResultsAll 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.ConclusionIn 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.

【 授权许可】

Unknown   
© Mishra et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.