PROJECT SUMMARY Melioidosis is a tropical infection caused by inoculation, inhalation, or ingestion of the Gram-negative soil saprophyte and Tier 1 select agent Burkholderia pseudomallei (Bps). The overall melioidosis mortality rate exceeds 40% in endemic areas of southeast Asia such as northeast (NE) Thailand (despite appropriate treatment), and modeling indicates that 165,000 cases of human melioidosis occur annually worldwide. For decades, diagnosis of melioidosis has required culture of Bps from a clinical specimen. This may take several days, delaying appropriate treatment, and in many resource-limited settings the necessary microbiology facilities for bacterial culture and identification are not available. Few suitable non-culture-based diagnostics exist. Performing a case-control analysis nested within a prospective, single-center cohort study of patients hospitalized with infection (Ubon-Sepsis study), we have developed a five-metabolite signature in plasma that, in preliminary studies, has extremely high accuracy differentiating melioidosis from other causes of infection (misclassification error rate=2.0%, AUC=0.99). These results suggest that measuring a limited number of circulating metabolites during initial presentation has significant diagnostic potential for melioidosis. We hypothesize that this host metabolomic signature is a novel and accurate diagnostic tool in identifying patients with melioidosis. To test this potentially high impact hypothesis, we will leverage our singular expertise in melioidosis diagnostics and human immunology, and an unparalleled multi-center melioidosis research infrastructure in NE Thailand in the following specific aims: 1) Replicate the diagnostic accuracy of the five- metabolite melioidosis signature in plasma for the detection of melioidosis in additional cases in the Ubon- Sepsis study. 2) Validate the diagnostic accuracy of the five-metabolite melioidosis signature in plasma for the detection of melioidosis in an independent prospective multi-center study. 3) Use an unbiased approach to identify additional signatures of melioidosis in plasma. If our hypothesis is proven, the use of blood metabolites as a melioidosis diagnostic could greatly enhance our present approaches to identifying melioidosis. Subsequent development of this tool for clinical use could have a profoundly beneficial impact on the burden of this often-lethal infectious disease.