Prospective Analysis of Antibody Diagnostic Tests and TTS1 Real-Time PCR for Diagnosis of Melioidosis in Areas Where It Is Endemic.

Melioidosis is a tropical infectious disease caused by Burkholderia pseudomallei. Melioidosis is associated with diverse clinical manifestations and high mortality. Early diagnosis is needed for appropriate treatment, but it takes several days to obtain bacterial culture results. We previously developed a rapid immunochromatography test (ICT) based on hemolysin coregulated protein 1 (Hcp1) and two enzyme-linked immunosorbent assays (ELISAs) based on Hcp1 (Hcp1-ELISA) and O-polysaccharide (OPS-ELISA) for serodiagnosis of melioidosis. This study prospectively validated the diagnostic accuracy of the Hcp1-ICT in suspected melioidosis cases and determined its potential use for identifying occult melioidosis cases. Patients were enrolled and grouped by culture results, including 55 melioidosis cases, 49 other infection patients, and 69 patients with no pathogen detected. The results of the Hcp1-ICT were compared with culture, a real-time PCR test based on type 3 secretion system 1 genes (TTS1-PCR), and ELISAs. Patients in the no-pathogen-detected group were followed for subsequent culture results. Using bacterial culture as a gold standard, the sensitivity and specificity of Hcp1-ICT were 74.5% and 89.8%, respectively. The sensitivity and specificity of TTS1-PCR were 78.2% and 100%, respectively. The diagnostic accuracy was markedly improved if the Hcp1-ICT results were combined with TTS1-PCR results (sensitivity and specificity were 98.2% and 89.8%, respectively). Among patients with initially negative cultures, Hcp1-ICT was positive in 16/73 (21.9%). Five of the 16 patients (31.3%) were subsequently confirmed to have melioidosis by repeat culture. The combined Hcp1-ICT and TTS1-PCR test results are useful for diagnosis, and Hcp1-ICT may help identify occult cases of melioidosis.

Optimization and prospective evaluation of sensitive real-time PCR assays with an internal control for the diagnosis of melioidosis in Thailand.

IMPORTANCE: Melioidosis is a serious infectious disease caused by Burkholderia pseudomallei, an environmental Gram-negative bacterium. Early detection of B. pseudomallei infection is crucial for successful antibiotic treatment and reducing mortality rates associated with melioidosis. Bacteria culture is currently used to identify B. pseudomallei in clinical samples, but the method is slow. Therefore, there is a need for more accurate and sensitive molecular-based diagnostic methods that can detect B. pseudomallei in all sample types, including samples from blood. We developed an optimal DNA extraction method for B. pseudomallei from plasma samples and used an internal control for real-time PCR. We evaluated six PCR target genes and identified the most effective target for the early detection of B. pseudomallei infection in patients. To prevent delays in the treatment of melioidosis that can lead to fatal outcomes, we recommend implementing this new approach for routine early detection of B. pseudomallei in clinical settings.