Patricia Karthikeyan Anitha, Hoti Sugeerappa Laxmanappa, Kanungo Reba, Jambulingam Purushothaman, Shashikala Nair, Naik Ashok C
Research Scholar, Department of Microbiology and Immunology, Vector Control Research Centre, Puducherry, India.
Scientist 'G', Department of Microbiology, Regional Medical Research Centre, Belagavi, Karnataka, India.
J Clin Diagn Res. 2017 Aug;11(8):DC27-DC31. doi: 10.7860/JCDR/2017/26523.10519. Epub 2017 Aug 1.
Scrub typhus, an acute febrile illness, caused by , is an important cause of pyrexia of unknown origin in regions of endemicity. This disease is mostly underdiagnosed or misdiagnosed, the reasons for this being a combination of factors which include clinical manifestations that can mimic other infections, lack of easy and reliable diagnostic methods and variation among strains in endemic areas. Hence, easy and reliable methods of diagnosis will contribute to rapid identification and treatment of the infection.
The aim of the study was to compare four different methods of detection of scrub typhus and to identify one single test or a combination of tests detecting maximum number of cases.
One hundred and forty-five suspected scrub typhus cases were included in this study. Duration of fever and presence of eschar in each patient was noted down. Enzyme-Linked Immunosorbent Assay (ELISA) to detect Immunoglobulin M (IgM) antibodies and Polymerase Chain Reaction (PCR) to detect three genes of , namely, 56 kDa, 16S rRNA, and were done on these samples. The results of each test were analyzed to identify the test picking up maximum number of positive samples. Statistical analysis was performed using Chi-square test. The level of significance was set at p<0.05.
These tests showed that IgM ELISA (93%) and PCR (68%) picked up maximum number of positives. Statistical analysis performed using Chi-square test between the diagnostic assays showed that the p - value <0.001 was significant for IgM ELISA. Among the molecular markers, p-value was significant (<0.001) for PCR. Further analysis of eschar positivity and duration of fever also showed that PCR could detect DNA of the bacterium even in cases with 10 days of fever and this PCR was the best among the molecular markers used to detect the infection.
This study suggests that IgM detection by ELISA and conventional PCR, either in combination or alone, depending on the duration of fever, would enhance the diagnosis of scrub typhus.
恙虫病是一种由恙虫病东方体引起的急性发热性疾病，是流行地区不明原因发热的重要原因。这种疾病大多未得到充分诊断或被误诊，其原因是多种因素共同作用的结果，包括可能与其他感染相似的临床表现、缺乏简便可靠的诊断方法以及流行地区菌株的差异。因此，简便可靠的诊断方法将有助于快速识别和治疗感染。
本研究的目的是比较四种不同的恙虫病检测方法，并确定一种单一检测方法或一组检测方法，以检测出最多数量的病例。
本研究纳入了145例疑似恙虫病病例。记录了每位患者的发热持续时间和焦痂情况。对这些样本进行了酶联免疫吸附测定（ELISA）以检测免疫球蛋白M（IgM）抗体，以及聚合酶链反应（PCR）以检测恙虫病东方体的三个基因，即56 kDa、16S rRNA和58 kDa。分析了每项检测的结果，以确定检出阳性样本数量最多的检测方法。使用卡方检验进行统计分析。显著性水平设定为p<0.05。
这些检测表明，IgM ELISA（93%）和PCR（68%）检出的阳性数量最多。使用卡方检验对诊断检测方法进行的统计分析表明，IgM ELISA的p值<0.001具有显著性。在分子标志物中，58 kDa PCR的p值具有显著性（<0.001）。对焦痂阳性和发热持续时间的进一步分析还表明，58 kDa PCR即使在发热10天的病例中也能检测到细菌DNA，并且该PCR是用于检测感染的分子标志物中最好的。
本研究表明，根据发热持续时间，通过ELISA检测IgM和传统的58 kDa PCR，单独或联合使用，将提高恙虫病的诊断率。
