Melioidosis Queensland: An analysis of clinical outcomes and genomic factors

BACKGROUND: The clinical and genomic epidemiology of melioidosis varies across regions. AIM: To describe the clinical and genetic diversity of B. pseudomallei across Queensland, Australia. METHODS: Whole genome sequencing of clinical isolates stored at the melioidosis reference lab from 1996–2020 was performed and analysed in conjunction with available clinical data. RESULTS: Isolates from 292 patients were analysed. Bacteraemia was present in 71% and pneumonia in 65%. The case-fatality rate was 25%. Novel sequence types (ST) accounted for 51% of all isolates. No association was identified between the variable virulence factors assessed and patient outcome. Over time, the proportion of First Nation’s patients declined from 59% to 26%, and the proportion of patients aged >70 years rose from 13% to 38%. CONCLUSION: This study describes a genomically diverse and comparatively distinct collection of B. pseudomallei clinical isolates from across Queensland, Australia. An increasing incidence of melioidosis in elderly patients may be an important factor in the persistently high case-fatality in this region and warrants further investigation and directed intervention.