Melioidosis, a pyogenic infection that presents acutely or as a chronic infection, is caused by the soil-associated bacterium Burkholderia pseudomallei. Infection is acquired by inoculation or inhalation and is more common in patients with underlying chronic disease. It is endemic in the tropical belt. Although Sri Lanka is not considered as a country where melioidosis is endemic, an increasing number of cases have been reported recently. Definitive diagnosis requires the isolation of B. pseudomallei in culture from clinical specimens. However, the laboratory diagnosis of melioidosis in Sri Lanka and other under-resourced countries is limited by a lack of familiarity with the bacterium and a lack of facilities to accurately confirm the identity of the isolate. It is highly likely that melioidosis is under-diagnosed in this country. There is a need to increase awareness of this infection among clinicians and clinical microbiologists and improve laboratory facilities for the selective isolation and accurate identification of B. pseudomallei. In addition, studies are needed to determine the epidemiology of melioidosis in Sri Lanka.

Melioidosis is an emerging infection in Sri Lanka. Since the clinical presentation of melioidosis is not distinctive, a high index of clinical suspicion is required. Definitive diagnosis is usually made by isolation of the causative bacterium, Burkholderia pseudomallei, in culture. Although it is not a difficult bacterium to culture, initial identification of the isolate requires prior experience with B. pseudomallei. A case report of a patient with acute onset of lung abscess with a positive sputum culture for B. pseudomallei is presented.

Background Melioidosis is a potentially fatal infectious disease caused by Burkholderia pseudomallei and the disease is endemic in SoutheastAsia and Northern Australia. It has been confirmed as endemic in Sri Lanka. Genomic epidemiology of B. pseudomallei in Sri Lanka is largely unexplored. This study aims to determine the biogeography and genetic diversity of clinical isolates of B. pseudomallei and the phylogenetic and evolutionary relationship of Sri Lankan sequence types (STs) to those found in other endemic regions of Southeast Asia and Oceania. Methods The distribution of variably present genetic markers [Burkholderia intracellular motility A (bimA) gene variants bimABP/bimABM, filamentous hemagglutinin 3 (fhaB3), Yersinia-like fimbrial (YLF) and B. thailandensis-like flagellum and chemotaxis (BTFC) gene clusters and lipopolysaccharide O-antigen type A (LPS type A)] was examined among 310 strains. Multilocus sequence typing (MLST) was done for 84 clinical isolates. The phylogenetic and evolutionary relationship of Sri Lankan STs within Sri Lanka and in relation to those found in other endemic regions of Southeast t Asia and Oceania were studied using e BURST, PHYLOViZ and minimum evolutionary analysis. Results The Sri Lankan B. pseudomallei population contained a large proportion of the rare BTFC Clade (14.5%) and bimABM allele variant (18.5%) with differential geographic distribution. Genotypes fhaB3 and LPSA were found in 80% and 86% respectively. This study reported 43 STs (including 22 novel). e-BURST analysis which include all Sri Lankan STs (71) resulted in four groups, with a large clonal group (group 1) having 46 STs, and 17 singletons. ST1137 was the commonest ST. Several STs were shared with India, Bangladesh and Cambodia. Conclusion This study demonstrates the usefulness of high-resolution molecular typing to locate isolates within the broad geographical boundaries of B. pseudomallei at a global level and reveals that Sri Lankan isolates are intermediate between Southeast Asia and Oceania.

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