Adapting Microarray Gene Expression Signatures for Early Melioidosis Diagnosis

Abstract

Melioidosis is caused by Burkholderia pseudomallei and is predominantly seen in tropical regions. The clinical signs and symptoms of the disease are nonspecific and often result in misdiagnosis, failure of treatment, and poor clinical outcome. Septicemia with septic shock is the most common cause of death, with mortality rates above 40%. Bacterial culture is the gold standard for diagnosis, but it has low sensitivity and takes days to produce definitive results. Early laboratory diagnosis can help guide physicians to provide treatment specific to B. pseudomallei. In our study, we adapted host gene expression signatures obtained from microarray data of B. pseudomallei-infected cases to develop a real-time PCR diagnostic test using two differentially expressed genes, AIM2 (absent in melanoma 2) and FAM26F (family with sequence similarity 26, member F). We tested blood from 33 patients with B. pseudomallei infections and 29 patients with other bacterial infections to validate the test and determine cutoff values for use in a cascading diagnostic algorithm. Differentiation of septicemic melioidosis from other sepsis cases had a sensitivity of 82%, specificity of 93%, and negative and positive predictive values (NPV and PPV) of 82% and 93%, respectively. Separation of cases likely to be melioidosis from those unlikely to be melioidosis in nonbacteremic situations showed a sensitivity of 40%, specificity of 54%, and NPV and PPV of 44% and 50%, respectively. We suggest that our AIM2 and FAM26F expression combination algorithm could be beneficial for early melioidosis diagnosis, offering a result within 24 h of admission.

Whole Blood Transcriptome Analysis Reveals the Correlation between Specific Immune Cells and Septicemic Melioidosis

“…More importantly, no significant overlap between genes that are differentially expressed between B. pseudomallei and other infections was found, even when Staphylococcus aureus and Staphylococcus coagulase negative were removed. Analogue to our findings, Sangwichian et al found that two other bacterial infections were falsely identified as B. pseudomallei by real-time PCR, suggesting that it is difficult to differentiate melioidosis from other pathogenic infections by transcriptional analysis [ 20 ].…”

Use of Recombinant Escherichia coli Strains in Immunofluorescence Assays for Melioidosis Diagnosis

“…Tan and colleagues confirmed that 60% of acute or subacute melioidosis patients presented antibodies against TssM in the sera within 2 weeks after hospital admission [22]. Hemolysin-coregulated protein (Hcp1) is a serological candidate target that was previously developed for lateral-flow rapid diagnosis [9,11] and ELISA [31]; however, our findings demonstrate that the Hcp1 performances (sensitivity, NPV, and accuracy) and method agreement (k) are lower than TssM. No previous report has ever directly compared the potential of TssM and Hcp1 for melioidosis diagnosis in the same approach.…”

BipD of Burkholderia pseudomallei: Structure, Functions, and Detection Methods

“…The disadvantages of the serodiagnosis of BipD are the cross-reaction of BipD with other antibodies, the high seropositivity among the healthy population, and the fact that not all patients infected with B. pseudomallei produce sufficient levels of antibodies against BipD [ 64 , 66 ]. The main drawback of all the serological assays is that the antibodies can only be detected 7–14 days post-infection [ 33 ]. Thus, antibody-detection methods cause delays in both the diagnosis and treatment of melioidosis.…”

“…With regards to molecular methods, many types of polymerase chain reactions (PCRs) conducted by targeting various genes to detect B. pseudomallei have resulted in different limits of detection (LODs) [ 31 , 32 , 33 ]. PCR can produce false-negative results when tested on direct blood specimens due to low bacterial loads (<10 CFU/mL), which are usually below the detection limits of any PCR assay, and the presence of inhibitory substances in the blood [ 22 ].…”