Prevalence of Salmonella typhi among Patients with Febrile Illness in Rural and Peri-Urban Populations of Vellore Distri
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ORIGINAL RESEARCH ARTICLE
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Prevalence of Salmonella typhi among Patients with Febrile Illness in Rural and Peri-Urban Populations of Vellore District, as Determined by Nested PCR Targeting the Flagellin Gene Balaji Nandagopal,1 Sathish Sankar,1 Karthikeyan Lingesan,1 Kumarasekharan Chandrasekharan Appu,1 Baby Padmini,2 Gopalan Sridharan1 and Anil Kumar Gopinath3 1 Sri Narayani Hospital & Research Centre, Vellore, Tamil Nadu, India 2 Department of Laboratory Services, G. Kuppusamy Naidu Memorial Hospital, Coimbatore, Tamil Nadu, India 3 School of Biosciences and Technology, VIT University, Vellore, Tamil Nadu, India
Abstract
Background and Objective: Fever is one of the most common illnesses in all age groups in India. Typhoid fever is a continuing problem in developing countries such as India, which has poor sanitation facilities. The diagnosis of typhoid fever is still made by conventional culture-based isolation and identification. Serologic diagnostic tests, though widely used, have many deficiencies. Our objective was to investigate a molecular nested polymerase chain reaction (nPCR) technique to detect Salmonella typhi among patients with febrile illness in rural and peri-urban communities in Vellore district (Tamil Nadu, India). Methods: nPCR targeting the flagellin gene (fliC) was carried out using HotStar Taq DNA polymerase on DNA extracted from the buffy coat fraction of blood samples. Blood culture was done in a completely automated blood culture system, BacT/Alert, on prospectively collected blood samples. Relevant clinicopathologic data were obtained. Results: nPCR was found to have a lower limit of detection of 0.01 colony-forming units per milliliter. The prevalence of typhoid fever as estimated by nPCR was 4.7% in pyrexia of unknown origin (PUO) in the rural/peri-urban communities of Vellore district. The prevalence of S. typhi as estimated by blood culture was 2.0%, which was lower than the nPCR estimation. nPCR had sensitivity and specificity of 100% and 97.3%, respectively. The observed agreement between blood culture and nPCR was 0.973 and the Kappa coefficient was 0.59 (p < 0.0001). The frequency of typhoid fever as detected by nPCR was 4.35% among rural patients and 5.32% among peri-urban individuals. Conclusion: nPCR on DNA extracts of buffy-coat samples using HotStar Taq was found to be a valuable and specific technique for diagnosis of typhoid fever.
Background Febrile illness is the most common reason for patients attending hospitals in India.[1,2] Among the causes of febrile illness, typhoid fever continues to be a major clinical problem. The WHO estimates the load of typhoid fever in the Asian region to be 274 per 100 000 of population, posing a major health problem.[3] Because of insufficient diagnostic investigations and patients not seeking medical help in time, typhoid fever may remain undiagnosed for prolonged periods, resulting
in economic loss due to loss of productive man-hours and preventable mortality.[4] Diagnosis of t
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