Diversity of Vibrio parahaemolyticus in marine fishes of Bangladesh.

AIMS: To determine the occurrence, diversity, antibiotic resistance and biofilm formation of Vibrio parahaemolyticus isolated from marine fishes in Bangladesh. METHODS AND RESULTS: A total of 80 marine fishes were obtained from the local markets and examined for the presence of V. parahaemolyticus. All the isolated V. parahaemolyticus were characterized for the presence of virulence markers, thermostable direct hemolysin (TDH) or thermostable direct hemolysin related hemolysin (TRH). Isolates were serotyped and further characterized by enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) typing to analyse the genetic diversity. Moreover, biofilm formation and antibiotic resistance patterns were also determined. About 63·75% (51/80) of the tested marine fishes were contaminated with V. parahaemolyticus. From the contaminated fishes, 71 representatives V. parahaemolyticus were isolated and none of them harboured tdh and trh virulence genes. Nine different O-groups and seven different K-types were found by serological analysis and the dominant serotype was O5:KUT. In ERIC-PCR analysis, eight clusters (A-H) were found and the most common pattern was A (46·5%). All of the isolates were resistant to ampicillin and 78·9% of isolates were resistant to streptomycin. The highest biofilm formation was found at 37°C compared to 25°C and 4°C. CONCLUSION: Diverse V. parahaemolyticus are present in marine fishes in the local market of Bangladesh with antibiotic-resistant properties and biofilm formation capacity. SIGNIFICANCE AND IMPACT OF THE STUDY: The widespread prevalence of diverse V. parahaemolyticus in marine fishes is an issue of serious concern, and it entails careful monitoring to ascertain the safety of seafood consumers.

The public health significance of latrines discharging to groundwater used for drinking.

Faecal contamination of groundwater from pit latrines is widely perceived as a major threat to the safety of drinking water for several billion people in rural and peri-urban areas worldwide. On the floodplains of the Ganges-Brahmaputra-Meghna delta in Bangladesh, we constructed latrines and monitored piezometer nests monthly for two years. We detected faecal coliforms (FC) in 3.3-23.3% of samples at four sites. We differentiate a near-field, characterised by high concentrations and frequent, persistent and contiguous contamination in all directions, and a far-field characterised by rare, impersistent, discontinuous low-level detections in variable directions. Far-field FC concentrations at four sites exceeded 0 and 10 cfu/100 ml in 2.4-9.6% and 0.2-2.3% of sampling events respectively. The lesser contamination of in-situ groundwater compared to water at the point-of-collection from domestic wells, which itself is less contaminated than at the point-of-consumption, demonstrates the importance of recontamination in the well-pump system. We present a conceptual model comprising four sub-pathways: the latrine-aquifer interface (near-field); groundwater flowing from latrine to well (far-field); the well-pump system; and post-collection handling and storage. Applying a hypothetical dose-response model suggests that 1-2% of the diarrhoeal disease burden from drinking water is derived from the aquifer, 29% from the well-pump system, and 70% from post-collection handling. The important implications are (i) that leakage from pit latrines is a minor contributor to faecal contamination of drinking water in alluvial-deltaic terrains; (ii) fears of increased groundwater pollution should not constrain expanding latrine coverage, and (iii) that more attention should be given to reducing contamination around the well-head.

Detection of Vibrio cholerae O1 and O139 in environmental waters of rural Bangladesh: a flow-cytometry-based field trial.

Presence of Vibrio cholerae serogroups O1 and O139 in the waters of the rural area of Matlab, Bangladesh, was investigated with quantitative measurements performed with a portable flow cytometer. The relevance of this work relates to the testing of a field-adapted measurement protocol that might prove useful for cholera epidemic surveillance and for validation of mathematical models. Water samples were collected from different water bodies that constitute the hydrological system of the region, a well-known endemic area for cholera. Water was retrieved from ponds, river waters, and irrigation canals during an inter-epidemic time period. Each sample was filtered and analysed with a flow cytometer for a fast determination of V. cholerae cells contained in those environments. More specifically, samples were treated with O1- and O139-specific antibodies, which allowed precise flow-cytometry-based concentration measurements. Both serogroups were present in the environmental waters with a consistent dominance of V. cholerae O1. These results extend earlier studies where V. cholerae O1 and O139 were mostly detected during times of cholera epidemics using standard culturing techniques. Furthermore, our results confirm that an important fraction of the ponds' host populations of V. cholerae are able to self-sustain even when cholera cases are scarce. Those contaminated ponds may constitute a natural reservoir for cholera endemicity in the Matlab region. Correlations of V. cholerae concentrations with environmental factors and the spatial distribution of V. cholerae populations are also discussed.

A novel and simple mixture as point-of-use water treatment agent to produce safe drinking water.

BACKGROUND: People in rural Bangladesh have a poor understanding of the link between use of contaminated surface water and disease. An inexpensive point-of-use water treatment agent was developed to purify surface water. METHODS: Surface water was collected from various sources in Bangladesh from February 2007 to January 2008. Microbiological and physicochemical parameters of raw and treated surface water were analysed. Water was treated with a mixture of alum potash, bleaching powder and lime, or with each agent individually. RESULTS: Raw water was contaminated with bacteria, the counts for total coliforms, faecal coliforms and faecal streptococci being 26,431, 14,548 and 240 colony-forming units (cfu) 100 ml(-1), respectively. These counts fell to 0 cfu 100 ml(-1) after treatment with the mixture. The count of artificially introduced Vibrio cholerae was also reduced to 0 cfu 100 ml(-1) after treatment. Treatment of raw water altered the pH from 6.90 to 6.87, turbidity from 21.61 to 3.55 nephelometric turbidity units (NTU), residual chlorine from 0 to 0.09 mg litre(-1), conductivity from 124.03 to 229.96 µS cm(-1), and total dissolved solids from 59.40 to 199.25 mg litre(-1). All these results of treatment were within the range recommended by the WHO as acceptable for drinking water. CONCLUSION: The mixture of alum potash, bleaching powder and lime described can be safely used to disinfect contaminated surface water to make it suitable for drinking and other household purposes in Bangladesh.

Purification of household water using a novel mixture reduces diarrhoeal disease in Matlab, Bangladesh.

In Bangladesh, one of the main causes of waterborne diseases is related to the use of contaminated surface water. This pilot study was conducted to determine the acceptability and effectiveness of a recently developed surface water purifying mixture to prevent diarrhoeal diseases in a rural community in Bangladesh. The mixture, using a combination of alum potash, bleaching powder and lime, is added to 15 l of surface water and mixed; the water becomes suitable for drinking after 30 min. A total of 420 households from 15 villages were provided with the mixture and were taught how to use it. Episodes of diarrhoeal disease from study families were determined from hospital records of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) in Matlab and were compared with diarrhoea episodes among 1613 control families who were not provided with the mixture. A total of 83 diarrhoeal patients were treated at Matlab Hospital from 1613 control families, but only one patient was treated for diarrhoea from among the intervention families. Among the intervention families, 73 families decided to shift from using tube well water to surface water using the mixture. The mixture could be used as a cheaper, easier and simpler point-of-use water treatment strategy in Bangladesh.

Effects of local climate variability on transmission dynamics of cholera in Matlab, Bangladesh.

Cholera is considered as a model for climate-related infectious diseases. In Bangladesh, cholera epidemics occur during summer and winter seasons, but it is not known how climate variability influences the seasonality of cholera. Therefore, the variability pattern of cholera events was studied in relation to the variation in local climate variables in Matlab, Bangladesh. Classification and regression tree (CART) and principal component analysis (PCA) were used to study the dependency and variability pattern of monthly total cholera cases. An average temperature <23.25 degrees C corresponded to the lowest average cholera occurrence (23 cases/month). At a temperature of >or=23.25 degrees C and sunshine <4.13h/day, the cholera occurrence was 39 cases/month. With increased sunshine (>or=4.13h/day) and temperature (23.25-28.66 degrees C), the second highest cholera occurrence (44 cases/month) was observed. When the sunshine was >or=4.13h/day and the temperature was >28.66 degrees C, the highest cholera occurrence (54 cases/month) was observed. These results demonstrate that in summer and winter seasons in Bangladesh, temperature and sunshine hours compensate each other for higher cholera incidence. The synergistic effect of temperature and sunshine hours provided the highest number of cholera cases.

Serological diversity demonstrable by a set of monoclonal antibodies to eight serotypes of the mutans streptococci.

A set of monoclonal antibodies were prepared by the conventional cell fusion of myeloma cells (SP2/0-Ag14) with spleen cells from BALB/c mice immunised with whole cells of a strain of mutans streptococci. Their specificities were examined against 35 reference strains of mutans streptococci, 34 reference strains of other oral streptococci and 8 reference strains of other microorganisms often inhabiting the oral cavity. Specificity was examined by enzyme immunoassay using whole cells. A total of 52 strains, consisting of 19 strains isolated in Japan, 19 strains isolated in Italy and 14 strains isolated in England, were characterised by conventional physiological and biochemical tests and then serotyped by the use of 8 monoclonal antibodies with different specificities. They were also confirmed by guanine-plus-cytosine contents of their nucleic acid and DNA-DNA hybridisation test. The results indicated that all monoclonal antibodies are useful for identification of 8 serotypes of the mutans streptococci responsible for dental caries. They also suggest the existence of more serological varieties among mutans species.

Alterations in serum levels of trace elements in tuberculosis and HIV infections.

OBJECTIVE: To evaluate serum concentrations of trace elements in tuberculosis (TB) patients with or with out human immunodeficiency virus (HIV) coinfection before and after anti-TB chemotherapy. SUBJECTS: A total of 155 TB patients, 74 of which were coinfected with HIV, and 31 healthy controls from Gondar, Ethiopia. METHODS: Serum levels of copper, zinc, selenium and iron were determined using an inductively coupled plasma mass spectrometer from all subjects at baseline and from 44 TB patients (22 with HIV coinfection) at the end of an intensive phase of anti-TB chemotherapy. RESULTS: Compared with the control group, the concentrations of iron, zinc and selenium were significantly lower (P<0.05) while that of copper and copper/zinc ratio was significantly higher (P<0.05) in the serum of TB patients. TB patients with HIV coinfection had significantly lower serum zinc and selenium concentrations and significantly higher copper/zinc ratio compared to that in TB patients without HIV coinfection (P<0.05). The serum concentration of zinc had significantly increased at the end of intensive phase of anti-TB chemotherapy in patients without HIV coinfection (P<0.05). An increase in serum selenium level was observed in TB patients with or without HIV coinfection after therapy. On the contrary, serum copper concentration and copper/zinc ratio declined significantly after anti-TB chemotherapy irrespective of HIV serostatus (P<0.05). CONCLUSIONS: The results indicate that TB patients have altered profile of trace elements in their sera. This warrants the need for further investigations so that strategies for trace elements supplementation can be planned in addition to their potential as diagnostic parameters in monitoring responses to anti-TB chemotherapy.

Sequence analysis of TnphoA insertion sites in Vibrio cholerae mutants defective in rugose polysaccharide production.

Vibrio cholerae can switch from a smooth to a wrinkled or rugose colony phenotype characterized by the secretion of a polysaccharide that enables the bacteria to survive harsh environmental conditions. In order to understand the genetic basis of rugosity, we isolated TnphoA-induced stable, smooth mutants of two O1 El Tor rugose strains and mapped the insertion sites in several of the mutants using a modified Y-adapter PCR technique. One of the TnphoA insertions was mapped to the first gene of the vps region that was previously shown to encode the rugose polysaccharide biosynthesis cluster. Three insertions were mapped to a previously unknown hlyA-like gene, also in the vps region. Five other insertions were found in loci unlinked to the vps region: (i) in the epsD gene (encodes the "secretin" of the extracellular protein secretion apparatus), (ii) in a hydG-like gene (encodes a sigma(54)-dependent transcriptional activator similar to HydG involved in labile hydrogenase production in Escherichia coli, (iii) in a gene encoding malic acid transport protein upstream of a gene similar to yeiE of E. coli (encodes a protein with similarities to LysR-type transcriptional activators), (iv) in dxr (encodes 1-deoxy-D-xylulose 5-phosphate reductoisomerase), and (v) in the intergenic region of lpd and odp (encode enzymes involved in the pyruvate dehydrogenase complex formation). These data suggest the involvement of a complex regulatory network in rugose polysaccharide production and highlight the general utility of the Y-adapter PCR technique described here for rapid mapping of transposon insertion sites.