Siriphan BoonsilpJanjira ThaipadungpanitPremjit AmornchaiVanaporn WuthiekanunWirongrong ChierakulDirek LimmathurotsakulNicholas P. DaySharon J. PeacockMahidol UniversityFaculty of Medicine, Siriraj Hospital, Mahidol UniversityNuffield Department of Clinical MedicineUniversity of Cambridge2018-05-032018-05-032011-12-13BMC Infectious Diseases. Vol.11, (2011)147123342-s2.0-83255164933https://repository.li.mahidol.ac.th/handle/20.500.14594/12153Background: Pathogenic Leptospira spp. present in the blood of patients with leptospirosis during the first week of symptoms can be detected using culture or PCR. A proportion of patients who are positive by PCR are negative by culture. Leptospira spp. are fastidious bacteria, and we hypothesized that a false-negative culture result may represent infection with a distinct bacterial subset that fail to grow in standard culture medium.Methods: We evaluated our hypothesis during a prospective study of 418 consecutive patients presenting to a hospital in northeast Thailand with an acute febrile illness. Admission blood samples were taken for Leptospira culture and PCR. A single tube nested PCR that amplified a region of the rrs gene was developed and applied, amplicons sequenced and a phylogenetic tree reconstructed.Results: 39/418 (9%) patients were culture-positive for Leptospira spp., and 81/418 (19%) patients were culture-negative but rrs PCR-positive. The species associated with culture-positive leptospirosis (37 L. interrogans and 2 L. borgpetersenii) were comparable to those associated with culture-negative, PCR-positive leptospirosis (76 L. interrogans, 4 L. borgpetersenii, 1 unidentified, possibly new species).Conclusion: Molecular speciation failed to identify a unique bacterial subset in patients with culture-negative, PCR-positive leptospirosis. The rate of false-negative culture was high, and we speculate that antibiotic pre-treatment is the most likely explanation for this. © 2011 Boonsilp et al; licensee BioMed Central Ltd.Mahidol UniversityMedicineArticleSCOPUS10.1186/1471-2334-11-338