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Characterization of environmental Vibrio cholerae serogroups O1 and O139 in the Pearl River Estuary, China.

Authors
  • Li, Xiujun1
  • Wang, Duochun2
  • Li, Baisheng3
  • Zhou, Haijian2
  • Liang, Song4
  • Ke, Changwen3
  • Deng, Xiaoling3
  • Kan, Biao2
  • Morris, J Glenn Jr4
  • Cao, Wuchun5
  • 1 a School of Public Health Shandong University, Wenhuaxi Road, Shandong 250012, People's Republic of China. , (China)
  • 2 b Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, State Key Laboratory for Infectious Disease Prevention and Control, 155 Chang-Bai Street, Changping District, Beijing 102206, People's Republic of China. , (China)
  • 3 c Center for Diseases Control and Prevention of Guangdong Province, Guangzhou 510300, People's Republic of China. , (China)
  • 4 d Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA.
  • 5 e State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, People's Republic of China. , (China)
Type
Published Article
Journal
Canadian Journal of Microbiology
Publisher
Canadian Science Publishing
Publication Date
February 2016
Volume
62
Issue
2
Pages
139–147
Identifiers
DOI: 10.1139/cjm-2015-0443
PMID: 26674584
Source
Medline
Keywords
License
Unknown

Abstract

Toxigenic isolates of Vibrio cholerae serogroups O1 and O139 from aquatic reservoirs are a key source for recurrent epidemics of cholera in human populations. However, we do not have an optimal understanding of the microbiology of the strains within these reservoirs, particularly outside of the time periods when there are active cholera cases in the surrounding community. The main objective of the present study was to identify and characterize V. cholerae O1 and O139 in the Pearl River Estuary at a time when active disease was not being identified, despite prior occurrence of epidemic cholera in the region. Water samples were collected at 24 sites in the research area at monthly intervals between 2007 and 2010, and screened for the presence of V. cholerae O1 and O139. All isolates were screened for the presence of ctxAB, ompW, toxR, and tcpA genes. Multilocus variable number tandem repeat analysis (MLVA) was used to assess possible relationships among strains. The results show that Vibrio cholerae O1 or O139 was isolated, on average, from 6.7% of the sites screened at each time point. All V. cholerae O1 and O139 isolates were ctxAB negative, and 37% were positive for tcpA. Isolation was most common in the oldest, most urbanized district compared with other districts, and was associated with lower pH. Despite year-to-year variability in isolation rates, there was no evidence of seasonality. MLVA of 27 selected isolates showed evidence of high genetic diversity, with no evidence of clustering by year or geographic location. In this region where cholera has been epidemic in the past, there is evidence of environmental persistence of V. cholerae O1 and O139 strains. However, environmental strains were consistently nontoxigenic, with a high level of genetic diversity; their role as current or future agents of human disease remains uncertain.

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