Kevin L Schully1, Charles C Young2, Mark Mayo3, Amy L Connolly2, Vanessa Rigas3, Ammarah Spall1, Alyssa A Chan1, Mark G Salvador1, James V Lawler1, Jason A Opdyke4, Danielle V Clark1, Bart J Currie3,5. 1. Austere Environments Consortium for Enhanced Sepsis Outcomes, Biological Defense Research Directorate, Naval Medical Research Center-Frederick, Ft. Detrick. 2. Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland. 3. Global and Tropical Health Division, Menzies School of Health Research, Darwin, Australia. 4. Joint Program Executive Office for Chemical, Biological, Radiological and Nuclear Defense, Medical Countermeasure Systems, Ft. Detrick, Maryland. 5. Department of Infectious Diseases and Northern Territory Medical Program, Royal Darwin Hospital, Australia.
Abstract
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. Published by Oxford University Press for the Infectious Diseases Society of America 2018.
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 melioidosispatients, 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 melioidosispatients 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 melioidosispatients in Cambodia were classified correctly. Of great importance however, the assay detected capsule from blood samples for 32% of blood culture negative melioidosispatients in both cohorts and previously undiagnosed melioidosispatients 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. Published by Oxford University Press for the Infectious Diseases Society of America 2018.
Entities:
Keywords:
zzm321990 Burkholderia pseudomalleizzm321990 ; diagnostic; melioidosis; point of care