Indirect Detection of Burkholderia pseudomallei Infection in a US Marine After Training in Australia.

In 2012, the United States Marine Corps began annual deployments around Australia, including highly endemic areas for Burkholderia pseudomallei. B. pseudomallei infection, or melioidosis, is difficult to diagnose, and culture remains the gold standard. Accurate and timely diagnosis is essential, however, to ensuring appropriate therapy. Ten days after returning from Australia, a Marine presented to a community hospital with massive cervical lymphadenopathy, fever, and cough. Computed tomography demonstrated scattered pulmonary infiltrates with small cavitations; lymphadenopathy involving the cervical, supraclavicular, and mediastinal nodes; and splenomegaly. Sputum and blood cultures were negative. Empiric antimicrobial therapy with ceftazidime was initiated for suspected melioidosis. Retrospectively, a prototype iSTAT cartridge modified to detect B. pseudomallei capsular polysaccharide antigen was used to test a specimen of the patient's blood and was determined to be positive. Over the course of therapy, B. pseudomallei capsular antigen levels in blood declined as the patient improved. The leveraging of an existing point-of-care (POC) analyzer to create a rapid diagnostic assay for melioidosis provides a template for rapid POC diagnostics that could significantly improve the ability of clinicians to deliver timely and appropriate therapy for serious infections.

Serological evidence of Burkholderia pseudomallei infection in U.S. Marines who trained in Australia from 2012-2014: a retrospective analysis of archived samples.

Infection with the gram-negative bacterium Burkholderia pseudomallei can result in a life-threatening disease known as melioidosis. Historically, melioidosis was a common infection in military forces serving in Southeast Asia, and it has the potential to have a serious impact on force health readiness. With the U.S. Department of Defense's increasing strategic and operational focus across the Pacific Theater, melioidosis is an increasingly important issue from a force health protection perspective. U.S. Marines deploy annually to Darwin, Australia, a "hyperendemic" region for B. pseudomallei, to engage in training exercises. In an effort to assess the risk of B. pseudomallei infection to service personnel in Australia, 341 paired samples, representing pre- and post-deployment samples of Marines who trained in Australia, were analyzed for antibodies against B. pseudomallei antigens. Serological evidence of possible deployment-related infection with B. pseudomallei was found in 13 Marines. Future prospective studies are required to further characterize the risk to service members deployed to melioidosis endemic areas.

Next-generation Diagnostics for Melioidosis: Evaluation of a Prototype i-STAT Cartridge to Detect Burkholderia pseudomallei Biomarkers.

BACKGROUND: Infection with the gram-negative bacterium Burkholderia pseudomallei can result in melioidosis, a life-threatening disease that can be difficult to diagnose. Culture remains the gold standard for diagnosis but requires laboratory resources not available in many endemic regions. A lateral flow immunoassay has shown promise for POC diagnostics but suffers from low sensitivity when used on blood samples. PCR also has low sensitivity on blood, attributed to the low bacterial numbers in blood observed in melioidosis patients, even when bacteraemic. METHODS: A prototype i-STAT cartridge was developed to utilize the monoclonal antibody specific for the capsule of pathogenic Burkholderia species employed on the LFI. The resulting POC assay was evaluated on 414 clinical specimens from Darwin, Australia and Cambodia. RESULTS: The i-STAT assay accurately distinguished Australian blood culture positive melioidosis patients from Australian patients hospitalized with other infections (AUC = 0.91, 95% CI 0.817 - 1.0). We derived an assay cutoff with 76% sensitivity and 94% specificity that correctly classified 88% (n = 74) of the Australian patients. Interestingly, only 46% (6/13) of the culture-positive melioidosis patients in Cambodia were classified correctly. Of great importance however, the assay detected capsule from blood samples for 32% of blood culture negative melioidosis patients in both cohorts and previously undiagnosed melioidosis patients in Cambodia. In addition the assay showed high sensitivity and specificity for urine, pus and sputum. CONCLUSIONS: Diagnostic tools that are not dependent upon the growth kinetics or the levels of bacteremia of B. pseudomallei represent the next-generation of diagnostics and must be pursued further.