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Biochemical tests commonly used to screen for Vibrio cholerae in environmental samples were evaluated, and we found that a combination of alkaline peptone enrichment followed by streaking on thiosulfate citrate bile salts sucrose agar and testing for arginine dihydrolase activity and esculin hydrolysis was an effective rapid technique to screen for aquatic environmental V. cholerae . This technique provided 100% sensitivity and ≥70% specificity.

Between November 2010, and May 2011, eleven cases of cholera, unrelated to a concurrent outbreak on the island of Hispaniola, were recorded, and the causative agent, Vibrio cholerae serogroup O75, was traced to oysters harvested from Apalachicola Bay, Florida. From the 11 diagnosed cases, eight isolates of V. cholerae were isolated and their genomes were sequenced. Genomic analysis demonstrated the presence of a suite of mobile elements previously shown to be involved in the disease process of cholera (ctxAB, VPI-1 and -2, and a VSP-II like variant) and a phylogenomic analysis showed the isolates to be sister taxa to toxigenic V. cholerae V51 serogroup O141, a clinical strain isolated 23 years earlier. Toxigenic V. cholerae O75 has been repeatedly isolated from clinical cases in the southeastern United States and toxigenic V. cholerae O141 isolates have been isolated globally from clinical cases over several decades. Comparative genomics, phenotypic analyses, and a Caenorhabditis elegans model of infection for the isolates were conducted. This analysis coupled with isolation data of V. cholerae O75 and O141 suggests these strains may represent an underappreciated clade of cholera-causing strains responsible for significant disease burden globally.

Five tube-wells in Matlab, Bangladesh, were selected for analysis of selected biophysicochemical parameters. The results showed that all tube-well water samples contained zooplankton and bacteria. Results for some of the parameters were outside the accepted limits recommended by the World Health Organization for drinking water. It is concluded that water from tube-wells should be treated if used as drinking water.

Historically, most of the major epidemics or outbreaks of cholera around the world have originated in coastal regions. The most dramatic of recent outbreaks of cholera occurred in India and Bangladesh in 1991, followed by an outbreak of cholera after almost a century without cholera in South America in 1991. Both of these recent epidemics were reported first in the coastal regions of India and Peru, respectively. Cholera epidemics are seasonal, occurring during the spring and fall months. Outbreaks of cholera in noncholera epidemic areas have been ascribed to travel and shipping activities, but there is compelling evidence that V. cholerae always is present in the aquatic environment and proliferates under nonepidemic conditions while attached to, or associated with, eucaryotic organisms. It is hypothesized that climate directly influences the incidence and geographic distribution of the cholera bacterium.

Vibrio cholerae is indigenous to the aquatic environment, and serotype non-O1 strains are readily isolated from coastal waters. However, in comparison with intensive studies of the O1 group, relatively little effort has been made to analyze the population structure and molecular evolution of non-O1 V. cholerae . In this study, high-resolution genomic DNA fingerprinting, amplified fragment length polymorphism (AFLP), was used to characterize the temporal and spatial genetic diversity of 67 V. cholerae strains isolated from Chesapeake Bay during April through July 1998, at four different sampling sites. Isolation of V. cholerae during the winter months (January through March) was unsuccessful, as observed in earlier studies (J. H. L. Kaper, R. R. Colwell, and S. W. Joseph, Appl. Environ. Microbiol. 37:91–103, 1979). AFLP fingerprints subjected to similarity analysis yielded a grouping of isolates into three large clusters, reflecting time of the year when the strains were isolated. April and May isolates were closely related, while July isolates were genetically diverse and did not cluster with the isolates obtained earlier in the year. The results suggest that the population structure of V. cholerae undergoes a shift in genotype that is linked to changes in environmental conditions. From January to July, the water temperature increased from 3°C to 27.5°C, bacterial direct counts increased nearly an order of magnitude, and the chlorophyll a concentration tripled (or even quadrupled at some sites). No correlation was observed between genetic similarity among isolates and geographical source of isolation, since isolates found at a single sampling site were genetically diverse and genetically identical isolates were found at several of the sampling sites. Thus, V. cholerae populations may be transported by surface currents throughout the entire Bay, or, more likely, similar environmental conditions may be selected for a specific genotype. The dynamic nature of the population structure of this bacterial species in Chesapeake Bay provides new insight into the ecology and molecular evolution of V. cholerae in the natural environment.

Shigellosis due to Shigella sonnei is rare among people growing up and living in developing countries; however, infections due to S sonnei becomes more common than those due to S flexneri as societies develop economically. The relation between risk of S sonnei infection and economic development may be explained by the exposure of developing-country populations to Plesiomonas shigelloides. P shigelloides is often found in surface water, and one serotype (serotype 17) possesses a cell-wall lipopolysaccharide identical to that of S sonnei . Thus, exposure to P shigelloides by drinking contaminated water may immunise populations to S sonnei . As economic development occurs, water quality improves and populations become susceptible to S sonnei . Although drinking pure water has many advantages, immunisation against S sonnei may be one benefit of traditional water sources.

A collection of 13 strains of Vibrio mimicus, including both clinical and environmental isolates from different geographic regions, was examined for various toxins. One strain of environmental origin produced cholera-like toxin (CT) which was completely absorbed with anti-CT immunoglobulin G, five strains produced a haemolysin that cross-reacted with the thermostable direct haemolysin of V. parahaemolyticus and DNA from two strains hybridised with a DNA probe specific for the heat-stable enterotoxin of V. cholerae non-O1. Culture supernates of all strains produced a factor that was cytotoxic to Vero and Chinese hamster ovary cells. In this study, we were able to identify strains of V. mimicus that produced, or had the genetic potential to produce, several toxin types simultaneously. The role of these strains as genetic reservoirs is discussed.

Vibrio cholerae is an estuarine bacterium associated with a single peak of cholera (March-May) in coastal villages of Bangladesh.For anunknownreason, however, cholera occurs in a unique dual peak (March-May and September-November) pattern in the city of Dhakathat is bordered by a heavily polluted freshwater river system and flood embankment. In August 2007, extreme flooding was accompanied by an unusually severe diarrhea outbreak in Dhaka that resulted in a record high illness. This study was aimed to understand the unusual outbreak and if it was related to the circulation of a new V. cholerae clone. Nineteen V. cholerae isolated during the peak of the 2007 outbreak were subjected to extensive phenotypic and molecular analyses, including multilocus genetic screening by polymerase chain reaction (PCR), sequence-typing of the ctxB gene, and pulsed-field gel electrophoresis (PFGE). Factors associated with the unusual incidence of cholera were determined and analysis of the disease severity was done. Overall, microbiological and molecular data confirmed that the hypervirulent V. cholerae was O1 biotype El Tor (ET) that possessed cholera toxin (CT) of the classical biotype. The PFGE ( Not I) and dendrogram clustering confirmed that the strains were clonal and related to the pre-2007 variant ET from Dhaka and Matlab and resembled one of two distinct clones of the variant ETconfirmed to be present in the estuarine ecosystem of Bangladesh. Results of the analyses of both diarrheal case data for three consecutive years (2006-2008) and regional hydroclimatology over three decades (1980-2009) clearly indicate that the pattern of cholera occurring in Dhaka, and not seen at other endemic sites, was associated with flood waters transmitting the infectious clone circulating via the fecal-oral route during and between the dual seasonal cholera peaks in Dhaka. Circular river systems and flood embankment likely facilitate transmission of infectious V. cholerae throughout the year that leads to both sudden and off-season outbreaks in the densely populated urban ecosystem of Dhaka. Clonal recycling of hybrid ElTor with increasing virulence in a changing climate and in a region with a growing urban population represents a serious public health concern for Bangladesh. Keywords: Cholera; Vibrio cholerae; dual peak; flood; off-season; fecal-oral; clonal transmission (Published: 8 August 2011) Citation: Infection Ecology and Epidemiology 2011, 1 : 7273 - DOI: 10.3402/iee.v1i0.7273

Most cholera epidemics begin in coastal areas lending credence to the hypothesis that the marine environment serves as a reservoir for the vibrio. In many cases viable but non-culturable Vibrio cholerae O1 may survive for some time in marine waters and then end dormancy with an unknown trigger resulting in an outbreak. This study evaluated the potential of two monitoring systems--Sensitive Membrane Antigen Rapid Test (SMART) and Cholera Direct Fluorescent Antibody (DFA)--to serve as an early warning system for outbreaks. Samples were collected in the summer of 1996 from a series of sites in the Ebrie lagoon in Abidjan Ivory Coast. The only sample positive for V cholerae O1 by the SMART test was the small mesh-sized particulate sample taken from Koumassi. The DFA gave a positive result for the Koumassi sample as well as those of small mesh-sized particulates from Yopougon. Koumassi and Yopougon are the two areas in Abidjan where the most cholera cases occur. The remaining low-mesh and all large mesh-sized particulates were negative for V cholerae O1. Further research on where in the food chain the vibrios are most concentrated their autochthonous presence in the lagoon and how the infection is spread to humans is necessary to facilitate development of a public health strategy for the control of cholera in the area.

This study presents 21 species of Chlamydomonas , four species of Carteria , two species of each of Nephroselmis , Pyramidomonas and Scherffelia , and Collodictyon triciliatum , Polytoma minus , Tetrachloridium ? allorgei and Tetraselmis cordiformis . These species have been reported from some ponds of Mathbaria of Pirojpur and Bakerganj of Barisal districts in Bangladesh. Key words: Phytoplankton, New records, Bangladesh, Volvocales, Ponds DOI: 10.3329/bjpt.v14i1.518 Bangladesh J. Plant Taxon. 14(1): 1-12, 2007 (June)

Monthly seasonal diversity and abundance of zooplankton species at three ponds of Mathbaria were investigated from surface water column during January 2008 to December 2008. Thirty?six species of zooplankton were identified from the ponds. Among these, 25 belonged to rotifer, six were of protozoan, three were copepods and one each from cladocera and ostracoda. Nauplii (copepods) were the most abundant (39.09% in site 1, 36.81% in site 2, and 33.06% in site 3) group, while the ostracoda were the least abundant (0.1% in site 2) group. The relative abundance was maximum (39.09%) for nauplii and minimum (4.56%) for cladocera in site 1; maximum (36.81%) for nauplii and minimum (0.1%) for ostracoda in site 2; maximum (33.15%) for rotifer and minimum (1.17%) for Cladocera in site 3. The species of frequent occurrence (100%) were Cyclops sp. and copepoda nauplius. In Bangladesh, cholera outbreaks have two major peaks, one between March to May and other between August to October. This study shows that, seasonal diversity and abundance of zooplankton species varied with seasons, the zooplankton peaks coincide to the reported peak outbreak of cholera at the area. Key words: Seasonal diversity; Mathbaria; Zooplankton; Abundance DOI: http://dx.doi.org/10.3329/dujbs.v20i2.8977 DUJBS 2011; 20(2): 163-171

Thirteen species of Phacus hitherto not reported from Bangladesh have been described and illustrated. Freshwater ponds at southern districts of Pirojpur and Barisal revealed these presence of the species. Â Key words: Phytoplankton, New records, Bangladesh, Phacus, Ponds doi:10.3329/bjb.v37i1.1564 Bangladesh J. Bot. 37(1): 55-60, 2008 (June)

Bacterial numbers in surface water samples, collected randomly from six different water bodies, were estimated by acridine orange direct counting (AODC) and conventional culture-based heterotrophic plate counting (HPC). Bacterial genomic DNA was prepared from water samples by employing methods used for stool samples, including the population dynamics, were determined by primer extension of the 16S rDNA (V6/V8 region) using polymerase chain reaction (PCR), followed by denaturing gradient gel electrophoresis (DGGE), a metagenomic tool that is capable of separating unrelated DNAs based on the differences in their sequences and GC contents. The bacterial numbers in water samples ranged from 10 3 – 10 6 CFU/ mL for HPC and 10 4 – 10 7 cells/ mL for AODC, showing that a great majority of bacteria prevail as uncultivable which do not respond to culture methods that are used widely for tracking bacterial pathogens. The acridine orange-stained bacteria varied in sizes and shapes, and appeared either as planktonic (solitary) cells or as clusters of biofilms, showing the presence of diverse community under the epifluorescence microscope. The DGGE of the ca. 457 bp amplicons, as confirmed by agarose gel electrophoresis, produced bands that ranged in intensities and numbers from 18 to 31, with each band possibly indicating the presence of one or more closely related bacterial species. The enrichment of pathogenic bacteria in the aquatic ecosystem is known to precede the seasonal diarrhoeal outbreaks; therefore, bacterial community dynamics determined by Metagenomic 16S PCR-DGGE during pre-epidemic enrichment appears promising in predicting the upcoming diarrheal outbreaks. Key words: Metagenomics; 16S rDNA; PCR; DGGE; bacterial community dynamics DOI: http://dx.doi.org/10.3329/bjm.v27i2.9171 BJM 2010; 27(2): 46-50

This study presents 20 taxa of the genus Euglena and one species of the rare euglenoid genus Euglenocapsa. All these taxa are reported for the first time from some pond ecosystems of Mathbaria in Pirojpur and Bakerganj of Barisal districts of Bangladesh. Keywords: Phytoplankton, New records, Bangladesh, Euglena, Euglenocapsa, PondsDOI: 10.3329/bjpt.v15i1.910Bangladesh J. Plant Taxon. 15(1): 39-46, 2008 (June)

This study presents two species of Rhodomonas, four species of Chroomonas, six species of Cryptomonas and Cryptochrysis minor, Cyanomonas coeruleus, Chrysodidymus synuroideus and Mallomonas akrokomos. These species have been reported from some ponds of Mathbaria in Pirojpur and Bakerganj of Barisal district in Bangladesh. Â Key words: Phytoplankton, New records, Cryptomonads, Synuroids, Ponds doi:10.3329/bjb.v36i1.1549 Bangladesh J. Bot. 36(1): 53-59, 2007 (June)

The paper deals with a systematic account of 17 euglenoid phytoplakton. Of these, seven taxa belong to Lepocinclis and seven to Strombomonas . The other three taxa are Astasia cylindrical Pringsheim , A. pygmaea Skuja and Menoidium tremulum Skv . T he taxa are reported from some pond ecosystems located in Pirojpur and Barisal districts of Bangladesh. Keyword s : Phytoplankton, New records, Bangladesh, Lepocinclis , Strombomonas , Astasia , Menoidium , Ponds  DOI: 10.3329/bjpt.v15i2.1740  Bangladesh J. Plant Taxon. 15(2): 107-114, 2008 (December)

Investigation of pelagic plankton communities from some freshwater ponds of Pirojpur and Barisal districts revealed the presence of 17 species under the genus Trachelomonas Ehr. for the first time in Bangladesh. Key words: Phytoplankton, Trachelomonas, New records, Ponds, Bangladesh doi:10.3329/bjb.v37i2.1719 Bangladesh J. Bot. 37(2): 133-139, 2008 (December)

Integrative conjugative elements (ICEs) are a class of self-transmissible mobile elements that mediate horizontal gene transfer in bacteria, and play an important role in bacterial evolution. Since 1992, ICEs of the SXT/R391 family have been found to be widely distributed among Vibrio cholerae strains isolated in Asian countries. Here we describe ICEVchB33, an ICE found in the genomes of two V. cholerae O1 Eltor strains, one isolated in India, 1994, and the other from Mozambique, 2004. ICEVchB33 revealed a new genetic organization, different from other ICEs of the SXT/R391 family, demonstrating the genomic plasticity of these elements.

DOI: http://dx.doi.org/10.3329/ujzru.v29i1.9470UJZRU 2010; 29(1): 69-71

Attachment of Vibrio cholerae to the mucosal surface of the intestine is considered to be an important virulence characteristic. Vibrio cholerae, an autochthonous member of brackish water and estuarine bacterial communities, also attaches to crustacea, a significant factor in multiplication and survival of V. cholerae in nature. The ability of V. cholerae to attach to the gut wall of the blue crab (Callinectes sapidus) was examined, and attachment was observed only in the hindgut and not the midgut of crabs, confirming a requirement for chitin in the attachment of V. cholerae to invertebrate and zooplankton surfaces. The new finding of attachment of V. cholerae to the hindgut of crabs may be correlated with the epidemiology and transmission of cholera in the aquatic environment. The crab model may also prove useful in elucidating the mechanism(s) of ion transport in crustacea.

In contrast to strictly marine microorganisms or obligatory parasites dwelling in a constant environment, facultative pathogens that spend part of their life inside the host and part as free-living forms possess exquisitely robust osmoregulation. Their survival and persistence in highly variable conditions outside of the host defines the pathways and efficacy of transmission. Giant spheroplasts as a system for patch-clamp recording, previously developed for E. coli, already permitted detailed characterization of osmoprotective tension-activated channels in this organism, but homologous channels from other bacteria have never been recorded in their native setting. We have recently developed giant spheroplast preparations for Vibrio cholerae and Pseudomonas aeruginosa. The first patch-clamp survey of both organisms revealed channels with conductances and gating phenotypes similar to MscS and MscL of E. coli, with comparable tension midpoints. Conductive responses to saturating tension are dominated by MscL-like channels in both species. Analysis of genomes pointed to single orthologs of MscL and MscS in V. cholereae, but P. aeruginosa, in addition to MscL, possesses two mscS-like channel genes. Homology models reveal differences from E. coli channels in the distributions of charged and aromatic residues, underlying potentially different interactions with lipids. MS channels in both species are modulated by ampthipathic autoinducers (CAI-1 and PAI-1) from respective bacterial species, which shift their activation curves to the right on the tension scale. This apparently indirect effect mediated by a distorted lateral pressure profile in the membrane suggests that autoinducers easily partition into the cytoplasmic membranes of these bacteria and may not require special transport systems for entry. Amenability to patch-clamp recording for the two new bacterial species opens broad opportunities for studies of solute permeability and electrogenic transport in their membranes.