Molecular detection and speciation of pathogenic Leptospira spp. in blood from patients with culture-negative leptospirosis.

Journal article

BACKGROUND: 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.

Authors: Boonsilp, S; Thaipadungpanit, J; Amornchai, P; Wuthiekanun, V; Chierakul, W

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: BioMed Central
• Journal: BMC infectious diseases
• Volume: 11
• Issue: 1
• Pages: 338
• Publication date: 2011-01-01
• DOI: 10.1186/1471-2334-11-338
• EISSN: 1471-2334
• ISSN: 1471-2334
• Language: English
• Keywords: False Negative Reactions; Phylogeny; Humans; Thailand; Sequence Analysis, DNA; Leptospirosis; Prospective Studies; DNA, Bacterial; Leptospira; Polymerase Chain Reaction; Sensitivity and Specificity; Bacterial Typing Techniques