Evaluation of antigen-detecting and antibody-detecting diagnostic test combinations for diagnosing melioidosis.

Premjit Amornchai,Viriya Hantrakun,Narisara Chantratitra,Gumphol Wongsuvan,Prapit Teparrakkul,Surasakdi Wongratanacheewin,Nicholas P J Day,Vanaporn Wuthiekanun,T Eoin West,Mary N Burtnick,Paul J Brett,David P Aucoin,Direk Limmathurotsakul,Husain Poonawala

doi:10.1371/journal.pntd.0009840

Abstract

Melioidosis, an infectious disease caused by Burkholderia pseudomallei, is endemic in many tropical developing countries and has a high mortality. Here we evaluated combinations of a lateral flow immunoassay (LFI) detecting B. pseudomallei capsular polysaccharide (CPS) and enzyme-linked immunosorbent assays (ELISA) detecting antibodies against hemolysin co-regulated protein (Hcp1) or O-polysaccharide (OPS) for diagnosing melioidosis. We conducted a cohort-based case-control study. Both cases and controls were derived from a prospective observational study of patients presenting with community-acquired infections and sepsis in northeast Thailand (Ubon-sepsis). Cases included 192 patients with a clinical specimen culture positive for B. pseudomallei. Controls included 502 patients who were blood culture positive for Staphylococcus aureus, Escherichia coli or Klebsiella pneumoniae or were polymerase chain reaction assay positive for malaria or dengue. Serum samples collected within 24 hours of admission were stored and tested using a CPS-LFI, Hcp1-ELISA and OPS-ELISA. When assessing diagnostic tests in combination, results were considered positive if either test was positive. We selected ELISA cut-offs corresponding to a specificity of 95%. Using a positive cut-off OD of 2.912 for Hcp1-ELISA, the combination of the CPS-LFI and Hcp1-ELISA had a sensitivity of 67.7% (130/192 case patients) and a specificity of 95.0% (477/502 control patients). The sensitivity of the combination (67.7%) was higher than that of the CPS-LFI alone (31.3%, p<0.001) and that of Hcp1-ELISA alone (53.6%, p<0.001). A similar phenomenon was also observed for the combination of CPS-LFI and OPS-ELISA. In case patients, positivity of the CPS-LFI was associated with a short duration of symptoms, high modified Sequential (sepsis-related) Organ Failure Assessment (SOFA) score, bacteraemia and mortality outcome, while positivity of Hcp1-ELISA was associated with a longer duration of symptoms, low modified SOFA score, non-bacteraemia and survival outcome. A combination of antigen-antibody diagnostic tests increased the sensitivity of melioidosis diagnosis over individual tests while preserving high specificity. Point-of-care tests for melioidosis based on the use of combination assays should be further developed and evaluated.

Highlights

Melioidosis, an infectious disease caused by the Gram-negative bacterium Burkholderia pseudomallei, is endemic to and has high mortality in tropical developing countries [1]
Melioidosis is an infection caused by the Gram-negative bacterium Burkholderia pseudomallei
We previously demonstrated that a prototype lateral flow immunoassay (LFI) developed to detect B. pseudomallei capsular polysaccharide (CPS) had limited sensitivity (31.3%) but high specificity (98.8%) for diagnosing melioidosis among patients presenting with community-acquired infection or sepsis in northeast Thailand

Summary

Introduction

Melioidosis, an infectious disease caused by the Gram-negative bacterium Burkholderia pseudomallei, is endemic to and has high mortality in tropical developing countries [1]. Acquired infections result from exposure through skin inoculation, inhalation or ingestion of B. pseudomallei, which is commonly present in soils and surface water in tropical countries [1,2]. Patients commonly present with sepsis, which is a syndrome defined by a dysregulated host response to infection resulting in significant organ dysfunction and death. A recent study in Thailand showed that there were 7,126 culture-confirmed melioidosis patients diagnosed from 2012 to 2015 in 70 hospitals countrywide, and that 39% of them died [4]. Melioidosis, an infectious disease caused by Burkholderia pseudomallei, is endemic in many tropical developing countries and has a high mortality. We evaluated combinations of a lateral flow immunoassay (LFI) detecting B. pseudomallei capsular polysaccharide (CPS) and enzyme-linked immunosorbent assays (ELISA) detecting antibodies against hemolysin co-regulated protein (Hcp1) or O-polysaccharide (OPS) for diagnosing melioidosis

Methods

Results

Discussion

Conclusion