Abstract
BackgroundThe Gram-negative soil dwelling bacterium Burkholderia pseudomallei is the etiological agent of melioidosis. The disease is endemic in most parts of Southeast Asia and northern Australia. Over last few years, there has been an increase in number of melioidosis cases from India; however the disease epidemiology is less clearly understood. Multi-locus sequence typing (MLST) is a powerful genotypic method used to characterize the genetic diversity of B. Pseudomallei both within and across the geographic regions.MethodsIn this study, MLST analysis was performed on 64 B. pseudomallei clinical isolates. These isolates were obtained between 2008–2014 from southwestern coastal region of India. Broad population patterns of Indian B. pseudomallei isolates in context with isolates of Southeast Asia or global collection was determined using in silico phylogenetic tools.ResultsA total of 32 Sequence types (STs) were reported among these isolates of which 17 STs (53%) were found to be novel. ST1368 was found as group founder and the most predominant genotype (n = 11, 17%). Most of the B. pseudomallei isolates reported in this study (or other Indian isolates available in MLST database) clustered in one major group suggesting clonality in Indian isolates; however, there were a few outliers. When analyzed by measure of genetic differentiation (FST) and other phylogenetic tools (e.g. PHYLOViZ), Indian STs were found closer to Southeast Asian isolates than Australian isolates. The phylogenetic analysis further revealed that within Asian clade, Indian isolates grouped more closely with isolates from Sri Lanka, Vietnam, Bangladesh and Thailand.ConclusionsOverall, the results of this study suggest that the Indian B. pseudomallei isolates are closely related with lesser heterogeneity among them and cluster in one major group suggesting clonality of the isolates. However, it appears that there are a few outliers which are distantly related to the majority of Indian STs. Phylogenetic analysis suggest that Indian isolates are closely related to isolates from Southeast Asia, particularly from South Asia.
Highlights
Melioidosis, caused by soil saprophyte Gram-negative bacterium Burkholderia pseudomallei, is classically characterized by pneumonia, septicemia and multiple abscesses
Most of the B. pseudomallei isolates reported in this study clustered in one major group suggesting clonality in Indian isolates; there were a few outliers
The results of this study suggest that the Indian B. pseudomallei isolates are closely related with lesser heterogeneity among them and cluster in one major group suggesting clonality of the isolates
Summary
Melioidosis, caused by soil saprophyte Gram-negative bacterium Burkholderia pseudomallei, is classically characterized by pneumonia, septicemia and multiple abscesses. Reports of melioidosis from India had been few and sporadic [3,4], over the past few years, there has been an increase in number of melioidosis cases. It has been reported from various states of India including Karnataka, Kerala, Maharashtra, Tamil Nadu and Puducherry [5]. There has been an increase in number of melioidosis cases from India; the disease epidemiology is less clearly understood. Multi-locus sequence typing (MLST) is a powerful genotypic method used to characterize the genetic diversity of B. Pseudomallei both within and across the geographic regions
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