How aware are we regarding vector borne diseases? A community based study in a slum of Kolkata, India

Background: Vector borne diseases (VBDs) form a major part of the communicable diseases in India. Ignorance and impoverished conditions of people contribute in creating source and spread of vector borne diseases and hinder disease control strategy. Slums are more vulnerable to vector borne diseases because of poor environmental condition, standard of living, poverty and ignorance of the people. This study is a small endeavour to highlight the awareness of residents of slum area of Chetla, Kolkata, West Bengal, India regarding vector borne diseases. Objectives were to assess the awareness of the study population regarding different vector borne diseases and to find out the association of awareness with relevant demographic variables.Methods: A community based observational, cross-sectional study was conducted among adult population in a slum area of Chetla, Kolkata, West Bengal, India. Multivariate logistic analysis was done to find out association of awareness with relevant variables.Results: Awareness regarding malaria was good and that of dengue was satisfactory while awareness regarding other vector borne diseases was poor. Age, sex, caste, education and social class were found significantly associated with satisfactory awareness. Younger population i.e. age ≤35years, males, general caste people, literacy status above primary school and social class III and above had better awareness regarding vector borne diseases.Conclusions: This study uncovered the lacunae regarding awareness of the study population regarding vector borne diseases. It can be concluded that intensified efforts towards creating public awareness and mobilizing the community regarding the identified issues should be addressed

Vibrio cholerae Classical Biotype Is Converted to the Viable Non-Culturable State when Cultured with the El Tor Biotype

A unique event in bacterial epidemiology was the emergence of the El Tor biotype of Vibrio cholerae O1 and the subsequent rapid displacement of the existing classical biotype as the predominant cause of epidemic cholera. We demonstrate that when the El Tor and classical biotypes were cocultured in standard laboratory medium a precipitous decline in colony forming units (CFU) of the classical biotype occurred in a contact dependent manner. Several lines of evidence including DNA release, microscopy and flow cytometric analysis indicated that the drastic reduction in CFU of the classical biotype in cocultures was not accompanied by lysis, although when the classical biotype was grown individually in monocultures, lysisof the cells occurred concomitant with decrease in CFU starting from late stationary phase. Furthermore, uptake of a membrane potential sensitive dye and protection of genomic DNA from extracellular DNase strongly suggested that the classical biotype cells in cocultures retained viability in spite of loss of culturability. These results suggest that coculturing the classical biotype with the El Tor biotype protects the former from lysis allowing the cells to remain viable in spite of the loss of culturability. The stationary phase sigma factor RpoS may have a role in the loss of culturability of the classical biotype in cocultures. Although competitive exclusion of closely related strains has been reported for several bacterial species, conversion of the target bacterial population to the viable non-culturable state has not been demonstrated previously and may have important implications in the evolution of bacterial strain

Delayed loss of culturability of <i>O395</i>Δ<i>rpos</i> in cocultures with El Tor N16961.

<p>A. Growth of O395?<i>rpos</i> and O395 in cocultures with El Tor N16961. Data is represented as means ± SD, n = 3. B. O395Δ<i>rpos</i> and El Tor N16961 were grown separately for 24 hours and mixed in the ratio of about 1∶1. Samples were removed at the time of mixing (0 h), 36 hours and 48 hours after mixing and processed for confocal microscopy.</p

Viability assay of classical O395.

<p>O395 cells from mono- and co- cultures were sorted and stained with the dye JC-1 and analyzed by flow cytometry. Cells treated with CCCP for membrane depolarization was used as negative controls.</p

Reduction of CFU of classical biotype in cocultures is dependent on growth phase and pH.

<p><b>A.</b> Fold change in CFU of O395 at 9 h after mixing of (a) cultures of O395 and N16961 in logarithmic phase of growth, (b) logarithmic phase culture of O395 and late stationary phase culture (24 h) of N16961 (c) late stationary phase culture of O395 and logarithmic phase culture of N16961 and (d) late stationary phase cultures of O395 and N16961. Data is represented as means ± SD, n = 3. <b>B.</b> Classical O395 and El Tor N16961 were inoculated into standard LB medium or LB buffered to pH 7 and CFU of O395 was assayed at regular intervals. The experiment was repeated twice (ND <10⁴ CFU/ml).</p

Growth of <i>V. cholerae</i> classical O395 in monocultures and cocultures.

<p>The strain O395 was grown individually in monocultures or cocultured with El Tor N16961 (1∶1) and CFU of O395 was determined at regular intervals. Data is represented as means ± SD, n = 4.</p

Lysis of classical O395 when grown individually in monocultures or in cocultures with El Tor N16961 Δ<i>dns</i>Δ<i>xds</i> (DNase⁻).

<p>CFU of O395 and O395 DNA in the supernatant (sup) were estimated in monocultures (a) and cocultures (b). DNA released into the supernatant when CFU of O395 in individual cultures decreased approximately six fold and that in cocultures decreased >10000 fold is indicated. Data is represented as means ± SD, n = 3.</p

Flow cytometric analysis of cocultures.

<p>N16961 and GFP labeled O395 were grown separately for 24 hours, mixed (1∶1) and samples were removed from the cocultures for flow cytometric analyses at 24 hours (A), 48 hours (B) and 7 days (C) after mixing. D. The GFP labeled (b) and non- labeled cells (c) from the cocultures were separated by FACS at the time of mixing (0 h) and 24 hour after mixing, and CFU of each population was determined. O395 monocultures (a) were used as an experimental control. Plating efficiency was scored as CFU per particle sorted from each gated population. Data is represented as means ± SD, n = 3.</p