Suttisunhakul Vichaya, Wuthiekanun Vanaporn, Brett Paul J, Khusmith Srisin, Day Nicholas P J, Burtnick Mary N, Limmathurotsakul Direk, Chantratita Narisara
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
J Clin Microbiol. 2016 May;54(5):1259-68. doi: 10.1128/JCM.02856-15. Epub 2016 Feb 24.
Burkholderia pseudomallei, the causative agent of melioidosis, is an environmental bacillus found in northeast Thailand. The mortality rate of melioidosis is ∼40%. An indirect hemagglutination assay (IHA) is used as a reference serodiagnostic test; however, it has low specificity in areas where the background seropositivity of healthy people is high. To improve assay specificity and reduce the time for diagnosis, four rapid enzyme-linked immunosorbent assays (ELISAs) were developed using two purified polysaccharide antigens (O-polysaccharide [OPS] and 6-deoxyheptan capsular polysaccharide [CPS]) and two crude antigens (whole-cell [WC] antigen and culture filtrate [CF] antigen) of B. pseudomallei The ELISAs were evaluated using serum samples from 141 culture-confirmed melioidosis patients from Thailand along with 188 healthy donors from Thailand and 90 healthy donors from the United States as controls. The areas under receiver operator characteristic curves (AUROCC) using Thai controls were high for the OPS-ELISA (0.91), CF-ELISA (0.91), and WC-ELISA (0.90), while those of CPS-ELISA (0.84) and IHA (0.72) were lower. AUROCC values using U.S. controls were comparable to those of the Thai controls for all ELISAs except IHA (0.93). Using a cutoff optical density (OD) of 0.87, the OPS-ELISA had a sensitivity of 71.6% and a specificity of 95.7% for Thai controls; for U.S. controls, specificity was 96.7%. An additional 120 serum samples from tuberculosis, scrub typhus, or leptospirosis patients were evaluated in all ELISAs and resulted in comparable or higher specificities than using Thai healthy donors. Our findings suggest that antigen-specific ELISAs, particularly the OPS-ELISA, may be useful for serodiagnosis of melioidosis in areas where it is endemic and nonendemic.
类鼻疽杆菌是类鼻疽病的病原体，是在泰国东北部发现的一种环境杆菌。类鼻疽病的死亡率约为40%。间接血凝试验（IHA）用作参考血清学诊断试验；然而，在健康人背景血清阳性率较高的地区，其特异性较低。为提高检测特异性并缩短诊断时间，利用类鼻疽杆菌的两种纯化多糖抗原（O-多糖[OPS]和6-脱氧庚糖荚膜多糖[CPS]）以及两种粗抗原（全细胞[WC]抗原和培养滤液[CF]抗原）开发了四种快速酶联免疫吸附测定（ELISA）。使用来自泰国的141例经培养确诊的类鼻疽病患者的血清样本以及来自泰国的188名健康供体和来自美国的90名健康供体作为对照，对ELISA进行评估。使用泰国对照时，OPS-ELISA（0.91）、CF-ELISA（0.91）和WC-ELISA（0.90）的受试者工作特征曲线下面积（AUROCC）较高，而CPS-ELISA（0.84）和IHA（0.72）的较低。除IHA（0.93）外，使用美国对照时所有ELISA的AUROCC值与泰国对照相当。对于泰国对照，使用0.87的临界光密度（OD）时，OPS-ELISA的灵敏度为71.6%，特异性为95.7%；对于美国对照，特异性为96.7%。在所有ELISA中对另外120份来自结核病、恙虫病或钩端螺旋体病患者的血清样本进行了评估，结果显示其特异性与使用泰国健康供体时相当或更高。我们的研究结果表明，抗原特异性ELISA，尤其是OPS-ELISA，可能有助于在类鼻疽病的地方流行区和非流行区进行血清学诊断。
