Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Department of Microbiology, Faculty of Medicine and Melioidosis Research Center, Khon Kaen University, Khon Kaen, Thailand.
PLoS Negl Trop Dis. 2021 Nov 2;15(11):e0009840. doi: 10.1371/journal.pntd.0009840. eCollection 2021 Nov.
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.
METHODOLOGY/PRINCIPAL FINDINGS: 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.
CONCLUSIONS/SIGNIFICANCE: 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.
类鼻疽是一种由伯克霍尔德氏菌引起的传染病，在许多热带发展中国家流行，死亡率很高。在这里，我们评估了检测伯克霍尔德氏菌荚膜多糖（CPS）的侧向流动免疫测定（LFI）和检测抗溶血调节蛋白（Hcp1）或 O-多糖（OPS）抗体的酶联免疫吸附试验（ELISA）组合，用于诊断类鼻疽。
方法/主要发现：我们进行了一项基于队列的病例对照研究。病例和对照组均来自泰国东北部社区获得性感染和败血症的前瞻性观察研究（乌汶败血症）。病例包括 192 名临床标本培养出伯克霍尔德氏菌阳性的患者。对照组包括 502 名血培养出金黄色葡萄球菌、大肠杆菌或肺炎克雷伯菌或聚合酶链反应检测出疟疾或登革热阳性的患者。入院后 24 小时内采集的血清样本储存并使用 CPS-LFI、Hcp1-ELISA 和 OPS-ELISA 进行检测。在评估联合诊断检测时，如果两种检测均为阳性，则结果被认为是阳性。我们选择与 95%特异性相对应的 ELISA 截止值。使用 Hcp1-ELISA 的阳性截止 OD 值为 2.912，CPS-LFI 和 Hcp1-ELISA 的组合具有 67.7%（130/192 例病例患者）的敏感性和 95.0%（477/502 例对照患者）的特异性。组合的敏感性（67.7%）高于 CPS-LFI 单独（31.3%，p<0.001）和 Hcp1-ELISA 单独（53.6%，p<0.001）。这种现象在 CPS-LFI 和 OPS-ELISA 的组合中也观察到。在病例患者中，CPS-LFI 的阳性与症状持续时间短、改良序贯（脓毒症相关）器官衰竭评估（SOFA）评分高、菌血症和死亡率结局有关，而 Hcp1-ELISA 的阳性与症状持续时间长、改良 SOFA 评分低、非菌血症和生存结局有关。
结论/意义：抗原抗体联合诊断检测提高了类鼻疽诊断的敏感性，同时保持了高特异性。基于联合检测的类鼻疽即时检测应进一步开发和评估。
