Prakash Rishika, Negi Sanjay Singh, Bhargava Anudita, Sharma Kuldeep, Jagzape Tushar, Wasnik Preetam
Department of Microbiology, All India Institute of Medical Sciences (AIIMS), Raipur, India.
Department of Microbiology, All India Institute of Medical Sciences (AIIMS), Raipur, India.
Indian J Med Microbiol. 2022 Oct-Dec;40(4):510-515. doi: 10.1016/j.ijmmb.2022.08.005. Epub 2022 Aug 29.
Scrub typhus, caused by Orientia tsutsugamushi (O. tsutsugamushi) present nonspecific clinical features during manifestation of acute undifferentiated febrile illness (AUFI) to render its early diagnosis difficult. Accordingly, this study was undertaken to assess an in-house groEL PCR versus IgM ELISA for the diagnosis of scrub typhus and to genotypically characterise the randomly selected scrub typhus positive cases.
Blood samples, collected from two hundred twenty one (221) AUFI cases were subjected to groEL PCR and IgM ELISA for diagnosis of scrub typhus. Eleven randomly selected PCR positive cases were processed for DNA sequencing to determine the genetic diversity of O. tsutsugamushi in Chhattisgarh.
Scrub typhus prevalence of 35.2% were detected among AUFI cases using both in-house groEL PCR and IgM ELISA. PCR alone showed sensitivity, specificity, positive and negative predictive values of 66.6% (CI: 55.08-76.94), 100% (CI: 90 to 100),100% (CI: 93.15 to 100) and 57.37% (CI: 44.05 to 69.96) while for IgM ELISA, these parameters were 62.8% (CI: 51.13-73.50), 100% (CI: 90 to 100), 100% (CI: 92.75 to 100) and 54.68% (CI: 41.75 to 67.18) respectively. PCR and ELISA could detect scrub typhus in 37.2% and 33.3% cases, when tested alone. groEL PCR detected the O. tsutsugamushi throughout the course of infection. Phylogenetic analysis depicted 5 of 11 positive cases belonged to Kuroki, Japan strain of O. tsutsugamushi, followed by Gilliam and Karp strain in 4 and 2 cases respectively.
Scrub typhus should be considered in differential diagnosis of AUFI. groEL PCR may aid on to IgM ELISA test for optimum laboratory diagnosis of scrub typhus by its implementation especially in seronegative cases. Predominance of Kuroki-like strain followed by Gillian and Karp strains of O. tsutsugamushi in Chhattisgarh confirm variable geographical distribution of O. tsutsugamushi and provide the baseline epidemiological data which will eventually be used to help the researchers for developing better diagnostic tests and vaccine covering the predominant genotypes.
由恙虫病东方体引起的恙虫病在急性未分化热性病（AUFI）表现期间呈现非特异性临床特征，难以早期诊断。因此，本研究旨在评估一种内部groEL聚合酶链反应（PCR）与免疫球蛋白M（IgM）酶联免疫吸附测定（ELISA）用于恙虫病诊断，并对随机选择的恙虫病阳性病例进行基因分型特征分析。
从221例AUFI病例采集的血样进行groEL PCR和IgM ELISA以诊断恙虫病。对11例随机选择的PCR阳性病例进行DNA测序，以确定恰蒂斯加尔邦恙虫病东方体的遗传多样性。
使用内部groEL PCR和IgM ELISA在AUFI病例中检测到恙虫病患病率为35.2%。单独PCR显示敏感性、特异性、阳性和阴性预测值分别为66.6%（可信区间：55.08 - 76.94）、100%（可信区间：90至100）、100%（可信区间：93.15至100）和57.37%（可信区间：44.05至69.96），而对于IgM ELISA，这些参数分别为62.8%（可信区间：51.13 - 73.50）、100%（可信区间：90至100）、100%（可信区间：92.75至100）和54.68%（可信区间：41.75至67.18）。单独检测时，PCR和ELISA分别能在37.2%和33.3%的病例中检测到恙虫病。groEL PCR在感染全过程均可检测到恙虫病东方体。系统发育分析显示，11例阳性病例中有5例属于日本恙虫病东方体黑木株，其次分别有4例和2例属于吉利亚姆株和卡尔普株。
在AUFI的鉴别诊断中应考虑恙虫病。groEL PCR尤其在血清阴性病例中实施，可能有助于IgM ELISA试验以实现恙虫病的最佳实验室诊断。恰蒂斯加尔邦恙虫病东方体以黑木样株为主，其次是吉利亚姆株和卡尔普株，这证实了恙虫病东方体的地理分布存在差异，并提供了基线流行病学数据，最终将用于帮助研究人员开发更好的涵盖主要基因型的诊断试验和疫苗。
