Soil Sampling of Burkholderia pseudomallei in and around Mangalore, India - an Explorative Study

Research Article

J Bacteriol Mycol. 2017; 4(2): 1046.

Soil Sampling of Burkholderia pseudomallei in and around Mangalore, India - an Explorative Study

Chandrakar S* and Dias M

Department of Microbiology, Father Muller Medical College, India

*Corresponding author: Sagar Chandrakar, Department of Microbiology, Father Muller Medical College, India

Received: December 02, 2016; Accepted: March 15, 2017; Published: March 21, 2017


Introduction: Melioidosis is an infectious disease of public health importance caused by a saprophytic Gram-negative bacterium and a Tier 1 select agent, Burkholderia pseudomallei found in soil and water. It is endemic in countries in Southeast Asia including the Indian subcontinent and in northern Australia. Several cases have been reported across India but no attempt has been made to explore the habitat of Burkholderia pseudomallei from soil and water.

Aims: To determine the presence or absence of Burkholderia pseudomallei in the soil in Mangalore and its characterization using conventional and molecular methods.

Settings and Design: A prospective field study carried out for three seasons (Between November 2012 – August 2013).

Methods and Materials: In an exploratory study, soil samples were collected from multiple sites through three seasons (summer, winter, monsoon) systematically based upon presence of positive Melioidosis cases in the vicinity and screened for Burkholderia pseudomallei by culture methods and biochemical reactions. Isolated bacteria were confirmed later by latex agglutination test, 16S rDNA and TTS-1 (Type Three secretion system) Polymerase Chain Reaction (PCR) and MALDI-TOF mass spectrometry (Bruker).

Results: Out of samples collected from ten sites through three seasons, soil sample collected from one site post monsoon (winter) yielded Burkholderia pseudomallei.

Conclusion: We describe the first isolation of Burkholderia pseudomallei from the soil in western coastal region of India which will pave the path for future studies to describe the geographical niche and environmental factors affecting the Burkholderia pseudomallei distribution.

Keywords: Burkholderia pseudomallei; Mangalore; India; MALDI TOF; PCR; Soil


16SrDNA: 16subunit Ribosomal Deoxyribonucleic Acid; BP: Base Pair; B. pseudomallei: Burkholderia pseudomallei; DRDE: Defence Research & Development Establishment; DNA: Deoxyribonucleic Acid; HOD: Head of Department; ICMR: Indian Council of Medical Research; MALDI TOF: Matrix-Assisted Laser Desorption/ Ionization- Time of Flight; mm: Millimeters; PCR: Polymerase Chain Reaction; TBSS-C50: Threonine Basal Salt Plus Colistin 50 mg/L; TTSS: Type Three Secretion System; VNBC: Viable But Non Culturable.


Burkholderia pseudomallei, is a soil dwelling saprophyte and a causative agent of Melioidosis. It is found in environment much across south East Asia and northern Australia and increasing numbers being reported from new clusters including parts of South America [1]. Melioidosis occurs as a result of activities leading to increased exposure to environments containing B. pseudomallei. The route of infection may be through direct skin inoculation or contamination of wounds; although rarely transmission by inhalation and ingestion has also been reported [2]. Clinical spectrum ranges from a subclinical presentation to full blow septicaemia with fulminant septic shock with mortality up to 90% [3]. Due to its increased resistance, high mortality and potential aerosol transmission, it is being upgraded from Select B agent to Tier 1 Select Agent group, a group restricted for exceptionally virulent and dangerous pathogens [4].

B. pseudomallei have been commonly isolated from soil and water samples in the endemic areas of Thailand and northern Australia [5-8]. However, the geographical distribution of B. pseudomallei is still very unclear. Several positive melioidosis cases have been reported across India mainly from the western coastal Konkan belt of Karnataka despite which B. pseudomallei has never been isolated from soil or water samples in India [9]. Studies have shown a positive correlation between incidence of melioidosis and monsoon rains [2]. Environment studies have found increased melioidosis cases among paddy workers [10]. Citing the presence of similar environmental conditions such as temperature, precipitation and similar working culture, an environmental soil sampling was carried out to determine the presence of B. pseudomallei in order to identify the geographical distribution and map the risks it poses to humans and livestock [6].

Lately, there is an increase surge of reports of melioidosis cases from Mangalore and surrounding areas during the monsoon rains [9,11]. Hence this study is being taken up to record the influence of seasonal variation on its occurrence in the soil which may help in determining the magnitude of problem in Mangalore and surrounding areas. Soil sampling is important to identify the geographic areas where humans and animals are at risk of exposure and that aim of the study was achieved.


Sampling method

In an exploratory study, soil samples were collected from ten different sites in Mangalore (12.87°N, 74.88°E), a port town of Dakshina Kannada district, on the western coast of Karnataka, India (Figure 1). Since the study was carried out in an area where the presence/distribution of the B. pseudomallei was unknown, a pilot study was carried out with the sampling sites allocated based on the positive melioidosis cases documented over last two years. 50 soil samples were collected each for three consecutive seasons: Winter (November – January), Summer (February - May), Monsoon (June – October). First lot of soil sample collection was carried on 17 – 18 Nov 2012 followed by second on 20 – 21 April 2013 and third on 20 – 21 July 2013. The soil samples were collected within 100 meters from around household and working area, depending whether person was working outdoor or working from home such as in case of farmers or agriculturist, the soil was collected from the paddy fields whereas those with sedentary work, the soil was collected from around the household. No specific permissions were required for these locations/ activities as it did not involve any private land or any protected land.