Research Article: Burkholderia pseudomallei: Its Detection in Soil and Seroprevalence in Bangladesh

Date Published: January 15, 2016

Publisher: Public Library of Science

Author(s): Md. Shariful Alam Jilani, Jamshedul Alam Mohammad Robayet, Md. Mohiuddin, Md. Rokib Hasan, Chowdhury Rafiqul Ahsan, Jalaluddin Ashraful Haq, Pamela L. C. Small.

Abstract: BackgroundMelioidosis, caused by Burkholderia pseudomallei, is an endemic disease in Bangladesh. No systematic study has yet been done to detect the environmental source of the organism and its true extent in Bangladesh. The present study attempted to isolate B. pseudomallei in soil samples and to determine its seroprevalence in several districts in Bangladesh.Methodology and ResultsSoil samples were collected from rural areas of four districts of Bangladesh from where culture confirmed melioidosis cases were detected earlier. Multiple soil samples, collected from 5–7 sampling points of 3–5 sites of each district, were cultured in Ashdown selective media. Suspected colonies of B. pseudomallei were identified by biochemical and serological test, and by polymerase chain reaction (PCR) using 16s rRNA specific primers. Blood samples were collected from 940 healthy individuals of four districts to determine anti- B. pseudomallei IgG antibody levels by indirect enzyme linked immunosorbent assay (ELISA) using sonicated crude antigen. Out of 179 soil samples, B. pseudomallei was isolated from two samples of Gazipur district which is located 58 km north of capital Dhaka city. Both the isolates were phenotypically identical, arabinose negative and showed specific 550bp band in PCR. Out of 940 blood samples, anti- B. pseudomallei IgG antibody, higher than the cut-off value (>0.8), was detected in 21.5% individuals. Seropositivity rate was 22.6%-30.8% in three districts from where melioidosis cases were detected earlier, compared to 9.8% in a district where no melioidosis case was either detected or reported (p<0.01). Seropositivity increased with the advancement of age from 5.3% to 30.4% among individuals aged 1–10 years and > 50 years respectively. The seropositivity rates were 26.0% and 20.6% in male and female respectively, while it was 20–27% among different occupational groups. No significant association was observed with gender (χ2 = 3.441, p = 0.064) or any occupational group (χ2 = 3.835, p = 0.280).ConclusionThis is the first study demonstrating the presence of B. pseudomallei in the environmental (soil) samples of Bangladesh. It also suggested that a large proportion of people, residing in these districts, were exposed to the organism.

Partial Text: Melioidosis is an endemic disease of public health and clinical importance in tropical and subtropical regions of the world [1]. It is caused by a Gram negative saprophytic bacterium called Burkholderia pseudomallei. Infection occurs through skin and by inhalation when susceptible individuals are exposed to contaminated water and soil [2,3]. Melioidosis accounts for about 20% of all community-acquired septicemias in north-eastern Thailand and 2000 to 3000 new cases are diagnosed every year [4,5]. Multiple cases have also been reported from India and several countries of South-East Asia, the Middle East, Africa and South America [6].

The present study was carried out to isolate and identify B. pseudomallei in soil samples from four selected geographical areas of Bangladesh. The study also determined the presence of anti- B. pseudomallei IgG antibody to find out the seroprevalence of the infection in four districts of the country. B. pseudomallei was isolated in selective media, identified by biochemical tests, and finally confirmed by specific antisera and PCR. Serum IgG antibody to B. pseudomallei was determined by ELISA. Details of the methods are described below.

In Bangladesh, melioidosis has been infrequently detected for last the 25 years but no systematic epidemiologic information regarding its true magnitude and source is available. Isolation of the organism, B. pseudomallei, from clinical specimens indicates that the organism is present in our environment. However, its actual source has never been identified. The present study has been designed to isolate B. pseudomallei from the soil as well as to determine the seroprevalence among an apparently healthy population residing in four northern and northeastern districts of Bangladesh from where melioidosis cases were diagnosed previously.



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