Occurrence of Orientia Tsutsugamushi Genotypes in Areas of Union Territory of Puducherry and Tamil Nadu State, India

Abstract

Scrub typhus, caused by the proteobacterium, Orientia tsutsugamushi, is re-emerging in several regions of Asia, particularly in India. Severity of infection and clinical presentations are known to vary with the infecting prototype/ genotype. Hence genotypic characterization and distribution of various genotypes is of clinical and epidemiological importance. One hundred and forty five suspected scrub typhus cases, reporting to a tertiary care centre in Puducherry, India were investigated for O. tsutsugamushi specific IgM antibodies by ELISA out of which, 135 (93%) were positive. Most cases occurred post-monsoon, peaking in September, and there was a preponderance in young adults. Forty samples tested positive by Nested PCR based on 56kDa gene of O. tsutsugamushi and amplicons from PCR positive samples were sequenced. Phylogenetic tree constructed using 35 sequences (from nt 20 to nt 130) obtained in the study, along with those retrieved from NCBI site, formed two major branches; one comprising 15 sequences from this study, which aligned with Karp genotype, and the other containing 6 sequences which aligned with a sequence from Vellore, India. The second major branch had 12 sequences, which formed an independent group from the Gilliam prototype. Analysis of association of clinical manifestations with genotypes obtained in the present study showed that the sequences that formed an independent group, were associated with a wide spectrum of clinical manifestations involving multiple organs and more severe manifestations like ARDS and hypotension. The sequences, which branched with Karp prototype were associated with hepatitis, meningitis and Multi-organ disorder syndrome (MODS). The present study thus indicated that different genotypes of O. tsutsugamushi occur in southern regions of India, which were associated with various clinical manifestations. Studies on the occurrence of genotypes will help in development of diagnostic methods and vaccines to curtail the infection.

Application of Nested PCR and Loop-Mediated Isothermal Amplification (LAMP) to Target 56kDa gene in Scrub Typhus Patients and Phylogenetic Analysis to Identify Orientia tsutsugamushi Strains Circulating In and Around Puducherry

“…Karp is one of the major dominant genotypes of O. tsutsugamushi varying from 40-64.4% and it was reported in many countries. Regarding the genotypes of O. tsutsugamushi circulating in India, Patricia et al, 11 from Puducherry reported positivity of 42.9% for Karp and 17.1% for Kato. Usha et al, 10 from Andhra Pradesh also had a higher prevalence of Karp strains (70.4%) followed by Kawasaki (29.6%).…”

“…One of the studies from Pondicherry also proved that most of the sequences were matched with the Karp group strains. 11 A study was conducted by Patricia et al, 11 in Puducherry comprised that 15 of their sequences were correlated with the Karp group and another 6 from Vellore strains, respectively. They also indicated that 12 of their sequences form a separate group and did not match with the other genotypes that were included as a reference strain.…”

“…1 This can be overcome by new diagnostic assays viz., PCR, Nested PCR (N-PCR), Real Time PCR (qPCR) and Loop-Mediated Isothermal Amplification (LAMP) which helps in the early detection of O. tsutsugamushi DNA in blood samples. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] LAMP is one of the additional molecular methods for the rickettsial diagnosis and easy to perform, with four to six primers in isothermal temperature and it does not require any costly instruments. To the best of our knowledge, only a few reports are available in world database for the diagnosis of ST using LAMP.…”

Clinical, laboratory, and molecular epidemiology of Orientia tsutsugamushi infection from Southwestern India

“…In patients from Puducherry and Tamil Nadu, India, isolates close to Vellore were causing less severe infection with a narrow spectrum of infection and isolates close to Taiwan were causing much severe infection with multi-organ involvement including ARDS and hypotension. Karp was associated with hepatitis, meningitis and multiorgan dysfunction syndrome [ 21 ]. In contrast, Karp infected patients in our study had respiratory and cardiovascular involvement followed by severe thrombocytopenia.…”

Seroprevalence and Genotypic Characterization of Orientia tsutsugamushi in Febrile Pediatric Patients Admitted in Tertiary Care Hospital of Chennai, South India

“…26 Kato-like strains have been observed to be widespread throughout the country. 27 Studies from South India revealed a variable pattern of O. tsutsugamushi genotypes; one study identified Karp as the main strain 28 while another identified Gilliam as the dominant strain. 29 Kato was found to be a prevalent strain in a study from South India.…”