Rapid,actionable diagnosis of urban epidemic leptospirosis using a pathogenic Leptospira lipL32-based real-time PCR assay

Background: with a conservatively estimated 1 million cases of leptospirosis worldwide and a 5–10% fatality rate,the rapid diagnosis of leptospirosis leading to effective clinical and public health decision making is of high importance,and yet remains a challenge. methodology: based on parallel,population-based studies in two leptospirosis-endemic regions in brazil,a real-time pcr assay which detects lipl32,a gene specifically present in pathogenic leptospira,was assessed for the diagnostic effectiveness and accuracy. patients identified by active hospital-based surveillance in salvador and curitiba during large urban leptospirosis epidemics were tested. real-time pcr reactions were performed with dna-extracted samples obtained from 127 confirmed and 23 unconfirmed cases suspected of leptospirosis,122 patients with an acute febrile illness other than leptospirosis,and 60 healthy blood donors. principal findings: the pcr assay had a limit of detection of 280 leptospira genomic equivalents/ml. sensitivity for confirmed cases was 61% for whole blood and 29% for serum samples. sensitivity was higher (86%) for samples collected within the first 6 days after onset of illness compared to those collected after 7 days (34%). the real-time pcr assay was able to detect leptospiral dna in blood from 56% of serological non-confirmed cases. the overall specificity of the assay was 99%. conclusions: these findings indicate that real-time pcr may be a reliable tool for early diagnosis of leptospirosis,which is decisive for clinical management of severe and life-threatening cases and for public health decision making. © 2017 public library of science. all rights reserved.