Incidence of Vibrio cholerae and related vibrios in a coastal lagoon and seawater influenced by lake discharges along an annual cycle.

Most probable numbers of Vibrio cholerae and related vibrios were determined in Albufera Lake, Valencia, Spain, and in coastal waters under the influence of the lake discharges over the course of an annual cycle. The influence of temperature, kind of water, and characteristics of the different sampling sites on the numbers of vibrios recovered was evaluated. Maximum recovery of vibrios reached 10(3)/ml in both types of waters analyzed. V. cholerae numbers reached 10(3)/ml in the lake and 10(2) in one of the coastal sites. Frequently during the warm season, all vibrios isolated were identified as V. cholerae. Occasionally, no V. cholerae was recovered. The recovery of vibrios was significantly influenced by the temperature of the water and the type of water analyzed. Most of the V. cholerae isolates were included in Heiberg groups I and II, and nearly 50% of the strains used chitin as sole carbon source. Indole was not produced by 100% of the strains. All strains tested were non-O1 serovars.     

Prevalence of a Vibrio cholerae 18-kDa antigen in vibrios

Abstract An 18-kDa protein that occurs in Vibrio cholerae has been described as an in vivo and low-iron regulated outer membrane antigen. Monoclonal antibodies which recognized this antigen were protective as passive vaccines in the infant rabbit model of cholera disease. In this study, those monoclonal antibodies were used in three immunological assays for surveillance of various bacteria for the 18-kDa antigen. ELISA, and Western blot assays gave variable results with bacteria or outer membrane preparations. The biodot assay was the most sensitive test, detecting the 18-kDa antigen in 29 of 29 V. cholerae strains, independent of biotype or serotype. A few other Gram-negative bacteria and V. parahaemolyicus reacted weakly with our antibodies and antiserum.     

Lecithinase activity of Vibrio cholerae and of vibrios not agglutinated by O-cholera serum

The lecithinase activities of 187 V. cholerae strains differing in their virulence and 70 cultures of NAG vibrios of different origin varied in all experimental groups. The level of lecithinase activity in the groups of V. cholerae strains having low virulence, or no virulence at all, was considerably higher than in virulent strains. NAG vibrios isolated from diarrhea patients and from samples of lake and pond water did not differ in the activity of this enzyme.     

Incidence and toxigenicity of Vibrio cholerae in a freshwater lake during the epidemic of cholera caused by serogroup O139 Bengal in Calcutta, India

Abstract The extent of contamination of a freshwater lake with Vibrio cholerae 0139 Bengal and the toxigenicity of all the V. cholerae isolates recovered during the period of the study were examined during and after an explosive outbreak of 0139 cholera in Calcutta. Strains biochemically characterized as V. cholerae could be isolated throughout the period of study examined from the freshwater lake samples. Most probable number of V. cholerae belonging to the 0139 serogroup in surface waters was 3 to 4 per 100 ml during major part of the study but isolation of this serogroup from sediment and plankton samples was infrequent. Of the total of 150 strains recovered, 23 (15.3%) agglutinated with the 0139 antiserum while the remaining belonged to the non-O1 non-O139 serogroups. None of the strains agglutinated with the O1 antiserum. All the 23 strains of V. cholerae O139 produced cholera toxin while 7.9% of the 127 non-O1 non-O139 strains also produced cholera toxin. Resistance to ampilicillin, furazolidone and streptomycin was encountered among strains belonging to both V. cholerae O139 and V. cholerae non-O1 non-O139 strains, but the percentage of resistant strains in the former was much higher than in the latter. During this cholera epidemic, possibly due to the introduction of large numbers of toxigenic V. cholerae such as the O139 serogroup, there was an increase in the number of toxigenic vibrios among the innocuous aquatic residents. This presumably occured through genetic exchange and, if substantiated, could play an important role in the re-emergence of epidemics.     

Salinity and nutrients in a tropical coastal lagoon with groundwater discharges to the Gulf of Mexico

This study described the nutrient dynamics in a tropical coastal lagoon that is affected by the infiltration of cold nutrient-rich groundwater. The spatial and time variation of physicochemical characteristics (e.g., temperature, salinity, oxygen) and nutrients (e.g., nitrate, ammonium, soluble reactive silicate, soluble reactive phosphorus) are depicted and show changes with respect to weather conditions. The lagoon shows a permanent salinity gradient from the inner zone (14–19). Nitrate and soluble reactive silicate (SRSi) are inversely correlated with salinity. Soluble phosphorus (SRP) shows highest levels in the inner zone during winter months (>9 µM). Ammonium shows two high peaks, one in the rainy season (15 µM) and the other during winter (11 µM). The intensity and quality of rainfall influences the nitrate and SRSi inputs, while biological activity influences the SRP and ammonium levels.     

Direct detection of Vibrio cholerae and ctxA in Peruvian coastal water and plankton by PCR

Seawater and plankton samples were collected over a period of 17 months from November 1998 to March 2000 along the coast of Peru. Total DNA was extracted from water and from plankton grouped by size into two fractions (64 micro m to 202 micro m and >202 micro m). All samples were assayed for Vibrio cholerae, V. cholerae O1, V. cholerae O139, and ctxA by PCR. Of 50 samples collected and tested, 33 (66.0%) were positive for V. cholerae in at least one of the three fractions. Of these, 62.5% (n = 32) contained V. cholerae O1; ctxA was detected in 25% (n = 20) of the V. cholerae O1-positive samples. None were positive for V. cholerae O139. Thus, PCR was successfully employed in detecting toxigenic V. cholerae directly in seawater and plankton samples and provides evidence for an environmental reservoir for this pathogen in Peruvian coastal waters.     

Uptake of glutamate by Vibrio cholerae in media of low and high osmolarity, and in seawater

Uptake of glutamate by Vibrio cholerae was investigated in media of different osmotic pressure. Accumulation was higher at high osmotic pressures and most accumulation was within the first 6 min of incubation. Greater degradation of glutamate by cells incubated at low osmolarity was insufficient to account for the difference in accumulation levels. The results suggest the glutamate uptake may be important in adaptation of V. cholerae to high salinities such as encountered in estuarine and marine environments.     

Occurrence and distribution of Vibrio cholerae in the coastal environment of Peru

The occurrence and distribution of Vibrio cholerae in sea water and plankton along the coast of Peru were studied from October 1997 to June 2000, and included the 1997-98 El Ni?o event. Samples were collected at four sites in coastal waters off Peru at monthly intervals. Of 178 samples collected and tested, V. cholerae O1 was cultured from 10 (5.6%) samples, and V. cholerae O1 was detected by direct fluorescent antibody assay in 26 out of 159 samples tested (16.4%). Based on the number of cholera cases reported in Peru from 1997 to 2000, a significant correlation was observed between cholera incidence and elevated sea surface temperature (SST) along the coast of Peru (P < 0.001). From the results of this study, coastal sea water and zooplankton are concluded to be a reservoir for V. cholerae in Peru. The climate-cholera relationship observed for the 1997-98 El Ni?o year suggests that an early warning system for cholera risk can be established for Peru and neighbouring Latin American countries.     

Uptake and retention of Vibrio cholerae non-O1, Salmonella typhi, Escherichia coli and Vibrio harvey by mussels in seawater.

Vibrio cholerae non O1 is known to persist in estuarine and freshwater environments. Experiments evaluated the amount of microorganisms accumulated in mussels maintained in static seawater, contaminated with 10(4) to 10(6) cells/ml and the depuration time required in circulating water. Accumulation and retention times were compared with those for Escherichia coli, Salmonella typhi and Vibrio harvey. E. coli and S. typhi accumulated to a greater extent and were released from mussels more quickly than vibrios which became undetectable 2 to 3 days later than E. coli. Seasonal seawater temperatures (14 to 21 degrees C) had a limited influence on depuration but vibrios appear to be retained with more efficacy over 16 degrees C while E. coli and S. typhi were eliminated to a greater extent. When mussels were contaminated with mixed culture, vibrios appeared to predominate on E. coli, while no interference was observed between E. coli and S. typhi.     

Microbially — related redox changes in a subtropical lake I.In situ monitoring of the annual redox cycle

Using a recently developedin situ multiprobe the redox development in the water column of warm-monomictic Lake Kinneret was investigated during three annual cycles. During the time when sulfide release into the meta- and hypolimnion is initiated, our measurements show a linear relationship, close to the thermodynamic function, between the platinum electrode potential and the amount of sulfide produced by the sulfate reducing bacteria. A change of this relationship during summer stratification coincides with the bloom of the phototrophic sulfur bacteriumChlorobium phaeobacteroides.     

Single-cell vs. bulk activity properties of coastal bacterioplankton over an annual cycle in a temperate ecosystem

The connections between single-cell activity properties of heterotrophic planktonic bacteria and whole community metabolism are still poorly understood. Here, we show flow cytometry single-cell analysis of membrane-intact (live), high nucleic acid (HNA) content and actively respiring (CTC+) bacteria with samples collected monthly during 2006 in northern Spain coastal waters. Bulk activity was assessed by measuring ³H-Leucine incorporation and specific growth rates. Consistently, different single-cell relative abundances were found, with 60–100% for live, 30–84% for HNA and 0.2–12% for CTC+ cells. Leucine incorporation rates (2–153 pmol L⁻¹ h⁻¹), specific growth rates (0.01–0.29 day⁻¹) and the total and relative abundances of the three single-cell groups showed marked seasonal patterns. Distinct depth distributions during summer stratification and different relations with temperature, chlorophyll and bacterial biovolume suggest the existence of different controlling factors on each single-cell property. Pooled leucine incorporation rates were similarly correlated with the abundance of all physiological groups, while specific growth rates were only substantially explained by the percentage of CTC+ cells. However, the ability to reduce CTC proved notably better than the other two single-cell properties at predicting bacterial bulk rates within seasons, suggesting a tight linkage between bacterial individual respiration and biomass production at the community level.     

Occurrence of Vibrio cholerae in Municipal and Natural Waters and Incidence of Cholera in Azerbaijan

Cholera, a waterborne disease caused by Vibrio cholerae, is an autochthonous member of the aquatic environment and predominantly reported from developing countries. Technical reports and proceedings were reviewed to determine the relationship between occurrence of V. cholerae in natural waters, including sources of municipal water, and cases of cholera in Azerbaijan. Water samples collected from different environmental sources from 1970 to 1998 were tested for V. cholerae and 0.73% (864/117,893) were positive. The results showed that in April of each year, when the air temperature rose by approximately 5°C, V. cholerae could be isolated. With each increase in air temperature, 6-8 weeks after, impact on cases of cholera was recorded. The incidence of cholera peaked when the air temperature reached >25°C during the month of September. It is concluded that a distinct seasonality in cholera incidence exists in Azerbaijan, with increased occurrence during warmer months.     

Detection and transformation of genome segments that differ within a coastal population of Vibrio cholerae strains

Vibrio cholerae is an autochthonous member of diverse aquatic ecosystems around the globe. Collectively, the genomes of environmental V. cholerae strains comprise a large repository of encoded functions which can be acquired by individual V. cholerae lineages through uptake and recombination. To characterize the genomic diversity of environmental V. cholerae, we used comparative genome hybridization to study 41 environmental strains isolated from diverse habitats along the central California coast, a region free of endemic cholera. These data were used to classify genes of the epidemic V. cholerae O1 sequenced strain N16961 as conserved, variably present, or absent from the isolates. For the most part, absent genes were restricted to large mobile elements and have known functions in pathogenesis. Conversely, genes present in some, but not all, California isolates were in smaller contiguous clusters and were less likely to be near genes with functions in DNA mobility. Two such clusters of variable genes encoding different selectable metabolic phenotypes (mannose and diglucosamine utilization) were transformed into the genomes of environmental isolates by chitin-dependent competence, indicating that this mechanism of general genetic exchange is conserved among V. cholerae. The transformed DNA had an average size of 22.7 kbp, demonstrating that natural competence can mediate the movement of large chromosome fragments. Thus, whether variable genes arise through the acquisition of new sequences by horizontal gene transfer or by the loss of preexisting DNA though deletion, natural transformation provides a mechanism by which V. cholerae clones can gain access to the V. cholerae pan-genome.     

Incidence of Vibrio parahaemolyticus in U.S. coastal waters and oysters

Oyster and seawater samples were collected seasonally from May 1984 through April 1985 from shellfish-growing areas in Washington, California, Texas, Louisiana, Alabama, Florida, South Carolina, Virginia, and Rhode Island which had been designated as approved or prohibited by the National Shellfish Sanitation Program. Fecal coliforms counts, aerobic plate counts, and Vibrio parahaemolyticus densities were determined for the samples. Mean V. parahaemolyticus density was more than 100 times greater in oysters than in water, whereas density of fecal coliforms was approximately 10 times higher in oysters. Seasonal and geographical distributions of V. parahaemolyticus were related to water temperature, with highest densities in samples collected in the spring and the summer along the Gulf coast. The synthetic DNA probe for thermostable direct hemolysin hybridized with 2 of 50 isolates, 1 of which was positive by the Kanagawa test.