Bart J. Currie

Description:Melioidosis is caused by the environmental pathogen Burkholderia pseudomallei. Among 1,331 patients with melioidosis during 1989-2023 in the Darwin Prospective Melioidosis Study in Australia, we identified 6 locally acquired cases caused by B. pseudomallei sequence type 46. Because of global transmission and expansion of endemicity, clinicians should increase awareness of melioidosis.

Description:Genomic diversity in pathogen populations is foundational for evolution and adaptation. Understanding population-level diversity is also essential for tracking sources and revealing detailed pathways of transmission and spread. For bacteria, culturing, isolating, and sequencing the large number of individual colonies required to adequately sample diversity can be prohibitively time-consuming and expensive. While sequencing directly from a mixed population will show variants among reads, they cannot be linked to reveal allele combinations associated with phylogenetic inheritance patterns. Here, we describe the theory and method for using population sequencing directly from a mixed sample, along with a minimal number of individually sequenced colonies, to describe the phylogenetic diversity of a population without haplotype reconstruction. To demonstrate the utility of population sequencing in capturing phylogenetic diversity, we compared isogenic clones to population sequences of Burkholderia pseudomallei from sputum of a single patient. Our results point to the pathogen population being highly structured, suggesting that for some pathogens, sputum sampling may preserve structuring in the lungs and thus present a noninvasive alternative to understanding colonization, movement, and pathogen/host interactions. We also analyzed population sequences of Staphylococcus aureus derived from different people and different body sites to reveal directionality of transmission between hosts and across body sites, demonstrating the power and utility for characterizing the spread of disease and identification of reservoirs at the finest levels. We anticipate that population sequencing and analysis can be broadly applied to accelerate research in a wide range of fields reliant on a foundational understanding of population phylogenetic diversity.

Description:Respiratory viral infection may increase infection with Burkholderia pseudomallei progressing to clinical disease (melioidosis). This data linkage study evaluated associations between melioidosis and SARS-CoV-2 or influenza. Among 160 melioidosis cases, there was no difference in risk factors, vaccine status, or disease severity between 17 with viral co-infection and 143 without.

Description:Introduction: Rheumatic heart disease (RHD) is underdiagnosed globally resulting in missed treatment opportunities and adverse clinical outcomes. We describe the protocol for a study which aims to co-design, implement and conduct an evaluation of a task-sharing approach to echocardiographic active case finding for early detection and management of RHD in high-risk settings in Australia and Timor-Leste. Methods and analysis: Echocardiograms will be obtained by trained local staff using hand-held echocardiographic devices employing the 'Single Parasternal Long Axis view with a Sweep of the Heart' (SPLASH) technique and interpreted by experts remote from the site of acquisition. Approximately 1500 children and pregnant women will be screened across high-risk communities in Australia and Timor-Leste over an 18-month period. The study will use a type II effectiveness-implementation hybrid design. A tailored package of implementation strategies will be co-designed with communities and health services and mapped onto a Theory of Change framework. The clinical effectiveness will be assessed as the change in the proportion of the target population that are prescribed secondary prophylaxis for RHD by the end of the study compared with baseline. The implementation will be assessed as the adoption, penetration, sustainability, fidelity and cost of the programme with a mixed-methods theory-based and economic evaluation. Data will include numbers of normal, abnormal and uninterpretable SPLASH echocardiograms obtained, numbers of participants progressing through the cascade of care, interviews with staff and programme costs. Ethics and dissemination: Ethical approval has been obtained from the Human Research Ethics Committee of the NT Department of Health and Menzies School of Health Research, Darwin (HREC-2022-4479), the Western Australian Aboriginal Health Ethics Committee (HREC-1237) and the Instituto Nasional Saude Publika Timor-Leste Ethics and Technical Committee (03-UEPD/INSP-TL/V/2023). Informed consent is required to be enrolled. Study findings will be disseminated in the communities involved and submitted for publication. Trial registration number: NCT06002243.

Description:Burkholderia pseudomallei is the causative agent of melioidosis, a disease highly endemic to Southeast Asia and northern Australia, though the area of endemicity is expanding. Cases may occur in returning travelers or, rarely, from imported contaminated products. Identification of B. pseudomallei is challenging for laboratories that do not see this organism frequently, and misidentifications by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) and automated biochemical testing have been reported. The in vitro diagnostic database for use with the Vitek MS has recently been updated to include B. pseudomallei and we aimed to validate the performance for identification in comparison to automated biochemical testing with the Vitek 2 GN card, quantitative real-time polymerase chain reaction (qPCR) targeting the type III secretion system, and capsular polysaccharide antigen detection using a lateral flow immunoassay (LFA). We tested a "derivation" cohort including geographically diverse B. pseudomallei and a range of closely related Burkholderia species, and a prospective "validation" cohort of B. pseudomallei and B. cepacia complex clinical isolates. MALDI-TOF MS had a sensitivity of 1.0 and specificity of 1.0 for the identification and differentiation of B. pseudomallei from related Burkholderia species when a certainty cutoff of 99.9% was used. In contrast, automated biochemical testing for B. pseudomallei identification had a sensitivity of 0.83 and specificity of 0.88. Both qPCR and LFA correctly identified all B. pseudomallei isolates with no false positives. Due to the high level of accuracy, we have now incorporated MALDI-TOF MS into our laboratory's B. pseudomallei identification workflow.IMPORTANCEBurkholderia pseudomallei causes melioidosis, a disease associated with high morbidity and mortality that disproportionately affects rural areas in Southeast Asia and northern Australia. The known area of endemicity is expanding and now includes the continental United States. Laboratory identification can be challenging which may result in missed or delayed diagnoses and poor patient outcomes. In this study, we compared mass spectrometry using an updated spectral database with multiple other methods for B. pseudomallei identification and found mass spectrometry highly accurate. We have therefore incorporated this fast and cost-effective method into our laboratory's workflow for B. pseudomallei identification.