Characterization of environmentalVibrio choleraeserogroups O1 and O139 in the Pearl River Estuary, China

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.

Characterization and Genetic Variation of Vibrio cholerae Isolated from Clinical and Environmental Sources in Thailand

“…suggested that the El Tor variant possessing the Classical biotype originated through recombination between the Classical and El Tor types of CTXϕ [49]. One hybrid strain of this study, MK14, originating from a river water sample, lacked the biotype-specific genes as well as the main virulence genes ( ctxAB and tcpA ), suggesting it to be a non-toxigenic strain and in agreement with previous reports [50, 51]. The non-toxigenic strains, however, have been responsible for causing mild to moderate diarrhea in human volunteers in clinical trials [2].…”

“…However, these strains harbored other virulence genes similar to non-O1/non-O139. Both chxA and TTSS genes were frequently found among non-O1/non-O139 pathogenic strains and associated with diarrhea [36, 51, 55]. However, the environmental O1 strains in this study harbored chxA gene (TC22) and TTSS (MK14), indicating virulence potential to cause disease.…”

Estimation of Vibrio Species Incidences and Antibiotic Resistance in Diarrhea Patients.

“…Moreover, continuous monitoring of antibiotic resistance is required to access b-lactam resistance trends as third-generation cephalosporinresistant Vibrio incidences are rare and anxiously alarming [11,14].…”

“…Vibrio species express several virulence factors such as toxins (ctxA, stn, OmpW, and toxR), colonization factors (lipopolysaccharides, flagellar components, outer membrane proteins, hemagglutinins, and tcpA), protease (hemolysins, cytolysins, thermolysins, and metalloproteases), and iron acquisition systems [9]. Cholera toxin encoded by ctxA gene has been isolated only from clinical strains and is utilized as an epidemiological marker to access toxigenic potential of Vibrio strains [10,11].…”

Volcanic activity controls cholera outbreaks in the East African Rift

“…This bacillus thrives in alkaline saline aquatic environments with high temperatures and rich in organic matter and plankton [1][2][3][4][5][6]. The bacillus is found in coastal areas, where fresh water from rivers mixes with salt water from the sea [1,2,[7][8][9][10]. Contamination frequently occurs via the consumption of water, fish, and other foods containing cholera bacilli [11][12][13].…”