{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T02:57:08Z","timestamp":1787021828820,"version":"build-2736575974"},"reference-count":27,"publisher":"Public Library of Science (PLoS)","issue":"2","license":[{"start":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T00:00:00Z","timestamp":1771459200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010269","name":"Wellcome Trust","doi-asserted-by":"publisher","award":["220690\/Z\/20\/Z"],"award-info":[{"award-number":["220690\/Z\/20\/Z"]}],"id":[{"id":"10.13039\/100010269","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosntds.org"],"crossmark-restriction":false},"short-container-title":["PLoS Negl Trop Dis"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>\n                      Murine typhus is a flea-borne disease caused by\n                      <jats:italic>Rickettsia typhi<\/jats:italic>\n                      that typically presents as an acute febrile illness. The diagnosis is often missed, leading to delays in appropriate treatment. A qPCR targeting a single gene (\n                      <jats:italic>ompB)<\/jats:italic>\n                      for\n                      <jats:italic>R. typhi<\/jats:italic>\n                      is widely used for diagnosis; however, it has low sensitivity for detecting bacterial DNA in patients\u2019 blood.\n                    <\/jats:p>\n                    <jats:p>\n                      We aimed to increase sensitivity of detection of\n                      <jats:italic>R. typhi<\/jats:italic>\n                      using qPCR by targeting a gene containing repetitive sequences,\n                      <jats:italic>sca2<\/jats:italic>\n                      (surface cell antigen 2)\n                      <jats:italic>.<\/jats:italic>\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methodology<\/jats:title>\n                    <jats:p>\n                      We compared diagnostic accuracy with the standard assay targeting single sequence\n                      <jats:italic>ompB<\/jats:italic>\n                      (outer membrane protein B). Specificity, sensitivity, and bacterial load measurement of both assays were compared using stored EDTA-anticoagulated buffy coat samples from 88 patients with febrile illness at Mahosot Hospital or provincial hospitals in Laos. Among these, 55 cases were confirmed as positive or negative by first culturing\n                      <jats:italic>Rickettsia<\/jats:italic>\n                      spp. from patients\u2019 EDTA blood, followed by assessment with IFA and\n                      <jats:italic>ompB<\/jats:italic>\n                      PCR, and buffy coat from 6 additional cases was confirmed by\n                      <jats:italic>ompB<\/jats:italic>\n                      PCR. Ten further positive cases were confirmed by IFA using paired sera, and 17 cases classified as negative for scrub typhus and murine typhus based on Rapid Diagnostic Test (RDT) results were included in the evaluation.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      The\n                      <jats:italic>sca2<\/jats:italic>\n                      qPCR assay showed 59.09% sensitivity (95% CI, 38.73-76.74%) and 100% specificity (93.98-100%) for detection of\n                      <jats:italic>R. typhi<\/jats:italic>\n                      . In comparison,\n                      <jats:italic>ompB<\/jats:italic>\n                      assay demonstrated 36.36% sensitivity (95% CI, 19.73-57.05%) and 100% specificity (95% CI 93.98-100%). DNA copy number determined using the\n                      <jats:italic>sca2<\/jats:italic>\n                      gene was approximately 2.933 log unit higher than that determined using\n                      <jats:italic>ompB<\/jats:italic>\n                      gene (median, 16,500 copies\/\u03bcL; IQR, 13,045\u201340,000 versus median, 19.25 copies\/\u03bcL; IQR, 11.11-56.62, P\u2009&lt;\u20090.0001).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>\n                      This study suggests qPCR targeting\n                      <jats:italic>sca2<\/jats:italic>\n                      increases frequency of detection of\n                      <jats:italic>R. typhi<\/jats:italic>\n                      in patients with low bacterial DNA concentrations.\n                    <\/jats:p>\n                  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