| Summary: | <p>Abstract</p> <p>Background</p> <p>Pathogenic <it>Leptospira </it>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. <it>Leptospira </it>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.</p> <p>Methods</p> <p>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 <it>Leptospira </it>culture and PCR. A single tube nested PCR that amplified a region of the <it>rrs </it>gene was developed and applied, amplicons sequenced and a phylogenetic tree reconstructed.</p> <p>Results</p> <p>39/418 (9%) patients were culture-positive for <it>Leptospira </it>spp., and 81/418 (19%) patients were culture-negative but <it>rrs </it>PCR-positive. The species associated with culture-positive leptospirosis (37 <it>L. interrogans </it>and 2 <it>L. borgpetersenii</it>) were comparable to those associated with culture-negative, PCR-positive leptospirosis (76 <it>L. interrogans</it>, 4 <it>L. borgpetersenii</it>, 1 unidentified, possibly new species).</p> <p>Conclusion</p> <p>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.</p>
|
|---|
