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BMC Infect Dis. 2011 Dec 13;11:338. doi: 10.1186/1471-2334-11-338.

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

Author information

1
Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.

Abstract

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.

PMID:
22151687
PMCID:
PMC3297668
DOI:
10.1186/1471-2334-11-338
[Indexed for MEDLINE]
Free PMC Article

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