Predictability of Vibrio cholerae in Chesapeake Bay

Abstract

Vibrio cholerae is autochthonous to natural waters and can pose a health risk when it is consumed via untreated water or contaminated shellfish. The correlation between the occurrence of V. cholerae in Chesapeake Bay and environmental factors was investigated over a 3-year period. Water and plankton samples were collected monthly from five shore sampling sites in northern Chesapeake Bay (January 1998 to February 2000) and from research cruise stations on a north-south transect (summers of 1999 and 2000). Enrichment was used to detect culturable V. cholerae, and 21.1% (n ‫؍‬ 427) of the samples were positive. As determined by serology tests, the isolates, did not belong to serogroup O1 or O139 associated with cholera epidemics. A direct fluorescent-antibody assay was used to detect V. cholerae O1, and 23.8% (n ‫؍‬ 412) of the samples were positive. V. cholerae was more frequently detected during the warmer months and in northern Chesapeake Bay, where the salinity is lower. Statistical models successfully predicted the presence of V. cholerae as a function of water temperature and salinity. Temperatures above 19°C and salinities between 2 and 14 ppt yielded at least a fourfold increase in the number of detectable V. cholerae. The results suggest that salinity variation in Chesapeake Bay or other parameters associated with Susquehanna River inflow contribute to the variability in the occurrence of V. cholerae and that salinity is a useful indicator. Under scenarios of global climate change, increased climate variability, accompanied by higher stream flow rates and warmer temperatures, could favor conditions that increase the occurrence of V. cholerae in Chesapeake Bay.Vibrio cholerae is both the causative agent of cholera and a natural inhabitant of the aquatic environment. Nearly 200 V. cholerae serogroups have been identified to date (70), but only two serogroups, serogroups O1 and O139, are associated with epidemic cholera. V. cholerae was first isolated from the Chesapeake Bay in the 1970s and was suggested to be an autochthonous member of the aquatic environment (17). Further studies demonstrated clearly that V. cholerae is, in fact, autochthonous to the Chesapeake Bay and to the aquatic environment in general (15,18,40). V. cholerae has since been detected in natural waters worldwide, including areas where clinical cases of cholera did not exist (32,38,43,69). These studies showed that the majority of environmental isolates of V. cholerae are members of non-O1, non-O139 serogroups. However, various non-O1, non-O139 V. cholerae strains have repeatedly been isolated from patients with diarrhea (20, 59) and have shown a capacity to provoke localized diarrheal outbreaks (2,19,53, 56).Colwell (15) proposed that the natural aquatic environment serves as the reservoir for V. cholerae and that it may play a critical role in pandemics of cholera. Horizontal gene transfer, which has been demonstrated in V. cholerae by Waldor and Mekalanos (66), has been proposed as a mechanism for the emergence of new pathogenic strain...

Growth of Vibrio cholerae O1 Ogawa Eltor in freshwater

“…It was argued that a shift of the average environmental temperature towards the range optimal for growth for pathogens, which is typically around 37 u C, would enable pathogenic bacteria to compete better for nutrients with the low temperature-adapted indigenous heterotrophic microbial flora. Supporting this hypothesis is that temperature is frequently reported to influence growth and occurrence of V. cholerae O1 in natural waters with low salinity (Huq et al, 2005;Louis et al, 2003). Also, the faecal indicator bacterium E. coli was reported to grow outside its host in tropical waters, but not at higher latitudes in the northern hemisphere, where the average annual water temperature is lower (Winfield & Groisman, 2003).…”

“…Earlier reports, based on the distribution of V. cholerae in estuarine water, had already indicated the preference of this pathogen for moderate salinity with respect to optimum conditions for growth (Huq et al, 2005;Louis et al, 2003;Miller et al, 1982). Also, microcosm studies, using artificial seawater and tryptone as a carbon source, had previously shown that V. cholerae exhibits highest specific growth rates at moderate salinity (Singleton et al, 1982a).…”

“…Accordingly, V. cholerae O1 was frequently detected in estuary and coastal waters, and growth in sterile-filtered natural seawater under defined laboratory conditions has been reported (Binsztein et al, 2004;Louis et al, 2003;Mourino-Perez et al, 2003;Worden et al, 2006). In addition, laboratory studies using artificial seawater demonstrated growth of V. cholerae O1 down to a salinity of 5 g l 21 (Singleton et al, 1982a, b).…”

“…Laboratory experiments showed a positive correlation between temperature and the metabolic activity of V. cholerae O1 in defined sea salt solution in a temperature range from 10 to 25 u C (Singleton et al, 1982a). Furthermore, a more frequent detection of V. cholerae O1 in estuary waters and a higher morbidity rate among people in Bangladesh was shown to be associated with increasing temperatures (Louis et al, 2003;Rodo et al, 2002).…”

Salinity and Temperature Effects on Physiological Responses of Vibrio fischeri from Diverse Ecological Niches

“…Thus, contrary to the competitive dominance observed in Euprymna, Vibrio symbionts in Sepiola are host generalists [16]. Other studies with bivalve and vertebrate hosts have also demonstrated that salinity and temperature influence host colonization [19][20][21][22], abundance and distribution [23][24][25], physiological state and survival [26][27][28], and the adhesive capabilities to host epithelia [29]. Hence, previous research has made it apparent that salinity and temperature influence all life cycle stages of Vibrio species, including the biogeography of free-living cells, host attachment with subsequent proliferation during symbiosis, and the alternative evolutionary trajectories available to different host ranges.…”