Nallan Krishnamoorthy, Kalidoss Bhuvaneshwari Chinnathambi, Jacob Eunice Swarna, Mahadevan Samyuktha Krishnasamy, Joseph Steny, Ramalingam Ramkumar, Renu Govindarajan, Thirupathi Balaji, Ramasamy Balajinathan, Gupta Bhavna, Rahi Manju, Rajaiah Paramasivan
ICMR-Vector Control Research Centre, Field Unit, 4, Sarojini Street, Madurai 625002, India.
Department of Microbiology, Government Medical College and Hospital, Thanjavur 613004, India.
Microorganisms. 2025 Feb 4;13(2):333. doi: 10.3390/microorganisms13020333.
Scrub typhus is a mite-borne, re-emerging public health problem in India, particularly in Tamil Nadu, South India. More than 40 serotypes of have been documented worldwide. However, the information on the circulation of its molecular sub-types in India is scanty. A retrospective study was conducted among serologically confirmed cases of scrub typhus. DNA isolated from blood was screened by a nested polymerase chain reaction (nPCR) targeting the GroEL and the 56 kDa type-specific antigen (TSA) genes. Out of 59 samples, 14 partial fragments of GroEL and the twelve 56 kDa genes were PCR-amplified and DNA-sequenced. The neighbor-joining (NJ) analysis indicated three distinct phylogenetic clades, including a novel genotype designated as -Thanjavur-Tamil Nadu (-TJTN, 9 nos. 64.3%); Karp-like (4 nos. 28.6%); and Kuroki-Gilliam type (1 no. 7.1%). Also, phylogenetic analysis of twelve 56 kDa variable domains (VDΙ-ΙΙΙ) of TSA gene sequences revealed a distinctive new genotypic cluster of eight samples (66.6%), and the remaining four (33.4%) were Karp-like genotypes. The Simplot analysis for the similarity and event of recombination testing elucidated the existence of the new genotype of the -TJTN cluster, which was undescribed so far, in the Kato and TA716 lineages. The significant findings recommend further studies to understand the ongoing transmission dynamics of different strains in vector mites, rodent hosts, and humans in this region.
恙虫病是一种由螨虫传播的、在印度重新出现的公共卫生问题，在印度南部的泰米尔纳德邦尤为严重。全球已记录了40多种血清型。然而，关于其分子亚型在印度传播的信息却很少。我们对血清学确诊的恙虫病病例进行了一项回顾性研究。通过针对GroEL和56 kDa型特异性抗原（TSA）基因的巢式聚合酶链反应（nPCR）对从血液中分离的DNA进行筛选。在59个样本中，14个GroEL部分片段和12个56 kDa基因被PCR扩增并进行DNA测序。邻接法（NJ）分析表明有三个不同的系统发育分支，包括一个新的基因型，命名为 -坦贾武尔-泰米尔纳德邦（-TJTN，9个，占64.3%）；类卡尔普型（4个，占28.6%）；以及黑木-吉列姆型（1个，占7.1%）。此外，对TSA基因序列的12个56 kDa可变区（VDΙ-ΙΙΙ）进行的系统发育分析揭示了一个由8个样本（66.6%）组成的独特新基因型簇，其余4个（33.4%）为类卡尔普基因型。相似性和重组检测的Simplot分析阐明了 -TJTN簇新基因型的存在，该基因型在加藤和TA716谱系中迄今未被描述。这些重要发现建议进一步开展研究，以了解该地区不同恙虫病株在媒介螨虫、啮齿动物宿主和人类中的传播动态。
