Unravelling the Molecular Epidemiology and Genetic Diversity among Burkholderia pseudomallei Isolates from South India Using Multi-Locus Sequence Typing.

Chaitanya Tellapragada,Vandana Ke,Aayushi Kamthan,Tushar Shaw,Vinod Bhat,Subodh Kumar,Chiranjay Mukhopadhyay,Axel Cloeckaert

doi:10.1371/journal.pone.0168331

Abstract

There is a slow but steady rise in the case detection rates of melioidosis from various parts of the Indian sub-continent in the past two decades. However, the epidemiology of the disease in India and the surrounding South Asian countries remains far from well elucidated. Multi-locus sequence typing (MLST) is a useful epidemiological tool to study the genetic relatedness of bacterial isolates both with-in and across the countries. With this background, we studied the molecular epidemiology of 32 Burkholderia pseudomallei isolates (31 clinical and 1 soil isolate) obtained during 2006–2015 from various parts of south India using multi-locus sequencing typing and analysis. Of the 32 isolates included in the analysis, 30 (93.7%) had novel allelic profiles that were not reported previously. Sequence type (ST) 1368 (n = 15, 46.8%) with allelic profile (1, 4, 6, 4, 1, 1, 3) was the most common genotype observed. We did not observe a genotypic association of STs with geographical location, type of infection and year of isolation in the present study. Measure of genetic differentiation (FST) between Indian and the rest of world isolates was 0.14413. Occurrence of the same ST across three adjacent states of south India suggest the dispersion of B.pseudomallei across the south western coastal part of India with limited geographical clustering. However, majority of the STs reported from the present study remained as “outliers” on the eBURST “Population snapshot”, suggesting the genetic diversity of Indian isolates from the Australasian and Southeast Asian isolates.

Highlights

Melioidosis, caused by soil saprophytic bacteria Burkholderia pseudomallei is a fatal infection among human and animals of the tropics
Distribution of the study isolates based on the clinical condition, geographical location, year of isolation are enlisted below (Table 1).Of the 32 isolates included in the analysis, 30 (93.7%) had novel allelic profiles that were not reported previously
Sequence type (ST) from the present study were all outliers to the STs from the rest of world except for ST 1372, which was a double- locus variant (DLV) of Sri Lankan STs 1134, 1138 and 1140

Summary

Introduction

Melioidosis, caused by soil saprophytic bacteria Burkholderia pseudomallei is a fatal infection among human and animals of the tropics. Soil types based on texture, pH, salinity and moisture content were reported to influence the presence of B.pseudomallei in soil[1] Exposure to this pathogen via inoculation, inhalation or ingestion can lead to diverse clinical manifestations and high case fatality, if left untreated. There was no consistency observed in the form of melioidosis (clinical presentations) reported among these sporadic cases across the country [4,5,6] Given this context, questions such as the following arise: a) whether the disease is restricted to a few geographical hot spots in the country or is it ubiquitously present? As an additional outcome we looked for an association between the circulating B.pseudomallei sequence type (ST) and the form of the disease among the infected

Materials and Methods

Results

Discussion