Background: Melioidosis is a potentially fatal infectious disease caused byBurkholderia pseudomalleiand the disease is endemic in Southeast Asia and Northern Australia. It has been confirmed as endemic in Sri Lanka. Genomic epidemiology ofB.pseudomalleiin Sri Lanka is largely unexplored. This study aims to determine the biogeography and genetic diversity of clinical isolates ofB.pseudomalleiand 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 [Burkholderiaintracellular motility A (bimA)gene variantsbimA_BP/bimA_BM, filamentous hemagglutinin 3 (fhaB3),Yersinia-like fimbrial (YLF) andB.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 Asia and Oceania were studied using e BURST, PHYLOViZ and minimum evolutionary analysis.Results: The Sri LankanB.pseudomalleipopulation contained a large proportion of the rare BTFC clade (14.5%) andbimA_BMallele variant (18.5%) with differential geographic distribution. GenotypesfhaB3 andLPSA 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 ofB.pseudomalleiat a global level and reveals that Sri Lankan isolates are intermediate between Southeast Asia and Oceania.

We reported the genetic evidence of circulating hantaviruses from small mammals captured in a chronic kidney disease of unknown etiology (CKDu) hotspot area of Sri Lanka. The high seroprevalence of anti-hantavirus antibodies against Thailand orthohantavirus (THAIV) has been reported among CKDu patients and rodents in Sri Lankan CKDu hotspots. We captured 116 small mammals from CKDu endemic regions in the Polonnaruwa District of Sri Lanka. Seven animals (five out of 11 Mus booduga and two out of 99 Rattus rattus) were PCR-positive for the hantavirus. A rat-borne sequence was grouped with a THAIV-like Anjozorobe virus. In contrast, Mus-borne sequences belonged to the THAIV lineage, suggesting a novel orthohantavirus species according to the phylogenetic analyses and whole-genome comparisons. Our genetic evidence indicates the presence of two THAIV-related viruses circulating in this CKDu endemic area, suggesting a basis for further investigations to identify the infectious virus in patients with CKDu and the CKDu induction mechanism of these viruses.

Objective: Chronic kidney disease (CKD) and chronic kidney disease of uncertain etiology (CKDu) are chronic kidney diseases that pose a significant health burden in Sri Lanka. Leptospirosis is a bacterial zoonosis that primarily damages renal tissues by colonization of Leptospira spp. in the renal tubules and is a suspected etiological agent of CKDu. Since Sri Lanka is an endemic for leptospirosis and outbreaks of the disease have been reported, this study aimed to determine the association between leptospirosis and chronic kidney disease in two geographically distinct regions of Sri Lanka, Badulla (CKDu endemic) and Kandy (CKDu non-endemic) districts. Results: Eighty-five patients with CKDu and 149 controls from Badulla and 49 patients with CKD and 135 controls from Kandy were serologically tested by microscopic agglutination test with a panel of 11 Leptospira serogroups. The seroprevalence rates for leptospirosis were 7.1% and 13.4% in the CKDu and control groups, respectively, in Badulla and 2.1% and 18.5% in the CKD and control groups, respectively, in Kandy. There were no statistically significant differences between demographic characteristics and leptospirosis seropositivity in the CKD and control groups in either Badulla or Kandy.

Antimicrobial resistance (AMR) poses a major global health challenge, with Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), remains a clinically significant pathogen due to its multidrug resistance and robust biofilm formation. These challenges have renewed attention toward antimicrobial fatty acids, which act primarily through bacterial membrane disruption rather than conventional intracellular targets. However, the biophysical mechanisms underlying their interactions with bacterial membranes aren’t fully understood. To investigate this, a previously validated Gram-positive supported lipid bilayer (SLB) platform was combined with Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) and time-lapse fluorescence microscopy to examine the membrane interaction behavior of saturated and unsaturated long-chain fatty acids above and below their respective critical micelle concentration (CMC). These results were validated with traditional in vitro assays using MRSA. Unsaturated fatty acids, specifically myristoleic acid (MOA) and palmitoleic acid (POA), showed markedly stronger bactericidal activity than their saturated counterparts, along with substantial antibiofilm activity. QCM-D measurements revealed distinct, concentration-dependent membrane disruption signatures, with MOA showing CMC-dependent membrane disruption, whereas POA induced membrane perturbation even below its CMC. Time-lapse fluorescence microscopy revealed distinct membrane morphological responses: MOA induced defect formation, whereas POA produced both defects and bright puncta suggestive of bud formation on the SLB at concentrations above the CMC. Collectively, the results demonstrate that long-chain unsaturated fatty acids function as effective membrane-active antimicrobials against MRSA. More broadly, this study highlights the value of integrating SLB-based biophysical analysis with biological assays to mechanistically resolve membrane-active antimicrobial behavior and structure–activity relationships.