Development of a real-time PCR assay for the diagnosis of scrub typhus cases in India and evidence of the prevalence of new genotype of O. tsutsugamushi

Bakshi, Diprabhanu; Singhal, Pradeep K.; Mahajan, S.; Subramaniam, Prasanna; Tuteja, Urmil; Batra, Harsh Vardhan

doi:10.1016/j.actatropica.2007.07.013

Cited by 35 publications

(26 citation statements)

References 24 publications

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“…Scrub typhus was confirmed based on one of these criteria: 1) a 4-fold increase in IgM or IgG antibody against pooled antigens of O. tsutsugamushi strain Karp, Kato, and Gilliam in paired sera (7-14 days apart) using the indirect immunofluorescence assay (IFA), 2 2) a single IFA with IgM or IgG antibody titer ≥ 1:400, [19][20][21] or 3) positive real-time polymerase chain reaction (PCR) targeting 47-kDa genes and/or nested PCR targeting 56-kDa genes in O. tsutsugamushi using DNA extracted from patient's buffy coat. 22,23 The screening dilution for IFA was 1:50, and positive samples on screening were further serially diluted (2-fold) from 1:50 to 1:6,400. Scrub typhus patients who had other coinfections were excluded from the analysis.…”

Section: Methodsmentioning

confidence: 99%

Scrub Typhus in Northeastern Thailand: Eschar Distribution, Abnormal Electrocardiographic Findings, and Predictors of Fatal Outcome

Thipmontree

Tantibhedhyangkul

Silpasakorn

et al. 2016

The American Society of Tropical Medicine and Hygiene

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Abstract. Scrub typhus is endemic in Thailand. Of the 495 patients with acute undifferentiated fever studied in Maharat Nakhon Ratchasima Hospital, Nakhon Ratchasima, Thailand, from June 1, 2011, to December 31, 2012, 146 patients (29.5%) had confirmed scrub typhus. The majority of cases were male, farmers, with the mean (±standard deviation) age of 54.1 ± 15.2 years. A total of 59 patients (40.4%) had eschar lesion. The commonest sites for an eschar in male patients were the perineum, inguinal, and buttock area; whereas in females, it was the head and neck area. Abnormal electrocardiogram was found in 39 of 79 patients (49.4%) with sinus tachycardia being the most frequent finding (17, 21.5%). A total of 73 patients (50%) had at least one complication. Myocarditis was the cause of complete heart block in a scrub typhus patient, and he fully recovered after receiving intravenous chloramphenicol treatment. The case fatality rate was 6.2% (nine deaths).The independent predictors for fatal outcome were age over 65 years (odds ratio [OR] = 14.49, 95% confidence interval [CI] = 1.26-166.44, P = 0.03), acute kidney injury (OR = 12.75, 95% CI = 1.77-92.07, P = 0.01), and hyperbilirubinemia (OR = 24.82, 95% CI = 2.12-286.61, P = 0.01). Early diagnosis and prompt appropriate treatment can improve the patient's outcome.

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Section: Methodsmentioning

confidence: 99%

Scrub Typhus in Northeastern Thailand: Eschar Distribution, Abnormal Electrocardiographic Findings, and Predictors of Fatal Outcome

Thipmontree

Tantibhedhyangkul

Silpasakorn

et al. 2016

The American Society of Tropical Medicine and Hygiene

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“…Phylogenetic trees constructed using specific DNA sequences derived from the 56-kDa antigen genes of multiple Orientia strains have been obtained by several research groups to show the genetic relationships of various strains [58,169,[186][187][188][189][190][191][192][193][194][195][196][197][198][199][200][201][202][203]. Comparison of isolates from Japan, for example, produced phylogenetic trees from sequence comparisons that were used to group the increasing numbers of isolates from humans, rodents, and mites derived from multiple epidemiological investigations within the regions of endemicity [194].…”

Section: Molecular Characterization Of Antigen Genes In Orientia Speciesmentioning

confidence: 99%

“…Comparison of isolates from Japan, for example, produced phylogenetic trees from sequence comparisons that were used to group the increasing numbers of isolates from humans, rodents, and mites derived from multiple epidemiological investigations within the regions of endemicity [194]. Similar studies have been performed in Taiwan [196], Malaysia [197], India [200], northern Thailand [188], and China [204].…”

Section: Molecular Characterization Of Antigen Genes In Orientia Speciesmentioning

confidence: 99%

“…It is unclear whether antibiotic resistance was involved in this case, and no isolation, antigenic, or genetic characterization is available from this outbreak. In a more recent outbreak, Bakshi et al [200] compared real-time PCR with nested PCR by using 66 blood samples collected from febrile patients in Himaschal Pradesh states. Real-time PCR compared favorably with nested PCR; 42 of 48 samples that were reactive in nested PCR were reactive in real-time PCR.…”

Section: Geographic Distribution Of Antigenic Typesmentioning

confidence: 99%

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Scrub Typhus: The Geographic Distribution of Phenotypic and Genotypic Variants ofOrientia tsutsugamushi

et al. 2009

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Orientia tsutsugamushi is the etiological agent of scrub typhus, an acute, mite-borne, febrile illness that occurs in the Asia-Pacific region. Historically, strain characterization used serological analysis and revealed dramatic antigenic diversity. Eyeing a recommendation of potential vaccine candidates for broad protection, we review geographic diversity and serological and DNA prevalences. DNA analysis together with immunological analysis suggest that the prototype Karp strain and closely related strains are the most common throughout the region of endemicity. According to serological analysis, approximately 50% of isolates are seroreactive to Karp antisera, and approximately one-quarter of isolates are seroreactive to antisera against the prototype Gilliam strain. Molecular methods reveal greater diversity. By molecular methods, strains phylogenetically similar to Karp make up approximately 40% of all genotyped isolates, followed by the JG genotype group (Japan strains serotypically similar to the Gilliam strain but genetically non-Gilliam; 18% of all genotyped isolates). Three other genotype groups (Kato-related, Kawasaki-like, and TA763-like) each represent approximately 10% of genotyped isolates. Strains genetically similar to the Gilliam strain make up only 5% of isolates. Strains from these groups should be included in any potential vaccine.

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“…The clinical presentations of the genotypic groups identified in the present study varied considerably and the group which formed an independent cluster along with Taiwan and Thailand isolates presented a broad range of clinical symptoms which ranged from mild features like headache, cough, abdominal pain and vomiting to more severe manifestations like hypotension and hepatitis. Two new genotypes have been reported from Himalayan region of India in an earlier study [31,32]. Yang et al reported 4 prototype/genotype strains (Karp, Kato, Kawasaki and Gilliam) and eleven different Taiwanese genotypes (Taiwan-A, B, C, D, E, G, H, J, N, O and P) based on RFLP analysis of the 56-kDa type-specific antigen (TSA) gene [33].…”

Section: Discussionmentioning

confidence: 99%

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

K¹,

Sl²,

Kanungo³

et al. 2017

J Emerg Infect Dis

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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.

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Development of a real-time PCR assay for the diagnosis of scrub typhus cases in India and evidence of the prevalence of new genotype of O. tsutsugamushi

Cited by 35 publications

References 24 publications

Scrub Typhus in Northeastern Thailand: Eschar Distribution, Abnormal Electrocardiographic Findings, and Predictors of Fatal Outcome

Scrub Typhus in Northeastern Thailand: Eschar Distribution, Abnormal Electrocardiographic Findings, and Predictors of Fatal Outcome

Scrub Typhus: The Geographic Distribution of Phenotypic and Genotypic Variants ofOrientia tsutsugamushi

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

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