Srinivasan Seethalakshmi, Menon Thangam
Department of Microbiology, Dr. A. L. Mudaliar PG Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai, Tamil Nadu, India.
Indian J Pathol Microbiol. 2017 Jan-Mar;60(1):70-73. doi: 10.4103/0377-4929.200043.
Scrub typhus is an acute febrile illness caused by Orientia tsutsugamushi. The disease is under-diagnosed in India, because of low index of suspicion and also due to its nonspecific presentation, and lack of confirmatory diagnostic tests.
This study was undertaken to diagnose scrub typhus in patients with undifferentiated fevers by serology and molecular methods.
A total of 68 blood samples were collected from patients clinically suspected to have scrub typhus. After transportation to the laboratory, the serum was separated from the blood and subjected to rapid card test. The ethylenediaminetetraacetic acid blood samples were subjected to DNA extraction using QIAamp DNA Mini Kit followed by nested polymerase chain reaction (nPCR).
24/68 (35.29%) cases showed the presence of antibody against scrub typhus by serology. 6/68 (8.8%) patients showed the presence of outer membrane protein antigen gene 56 kDa by nPCR. 5/24 serology positive cases showed the presence of 56 kDa outer membrane protein antigen gene by nPCR. A large number of cases positive by serology were negative by PCR which may indicate a low sensitivity of this test either due to low copy numbers or due to excess host DNA.
Delay in treatment may increase disease severity and leads to higher mortality. Thus, molecular methods of diagnosis may aid in the early diagnosis of infection and enable prompt treatment. This is the first report on the diagnosis of scrub typhus in the suburbs of Chennai using molecular methods and reemphasizes the need for increased awareness of rickettsial infections in rural areas.
恙虫病是由恙虫病东方体引起的一种急性发热性疾病。在印度，由于怀疑指数低、临床表现不具特异性以及缺乏确诊诊断试验，该疾病的诊断率较低。
本研究旨在通过血清学和分子方法诊断不明原因发热患者的恙虫病。
从临床怀疑患有恙虫病的患者中总共采集了68份血样。运送到实验室后，将血清与血液分离并进行快速卡片试验。使用QIAamp DNA Mini试剂盒对乙二胺四乙酸血样进行DNA提取，随后进行巢式聚合酶链反应（nPCR）。
24/68（35.29%）例患者血清学检测显示存在抗恙虫病抗体。6/68（8.8%）例患者nPCR检测显示存在56 kDa外膜蛋白抗原基因。5/24例血清学阳性病例nPCR检测显示存在56 kDa外膜蛋白抗原基因。大量血清学阳性病例PCR检测为阴性，这可能表明该检测的敏感性较低，原因可能是拷贝数低或宿主DNA过多。
治疗延迟可能会增加疾病严重程度并导致更高的死亡率。因此，分子诊断方法可能有助于早期诊断感染并实现及时治疗。这是关于在钦奈郊区使用分子方法诊断恙虫病的首份报告，并再次强调农村地区需要提高对立克次体感染的认识。
