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<jats:title>ABSTRACT</jats:title><jats:p>Pathogenic<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Leptospira</jats:named-content>spp., the causative agents of leptospirosis, are slow-growing Gram-negative spirochetes. Isolation of<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Leptospira</jats:named-content>from clinical samples and testing of antimicrobial susceptibility are difficult and time-consuming. Here, we describe the development of a new solid medium that facilitates more-rapid growth of<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Leptospira</jats:named-content>spp. and the use of this medium to evaluate the Etest's performance in determining antimicrobial MICs to drugs in common use for leptospirosis. The medium was developed by evaluating the effects of numerous factors on the growth rate of<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Leptospira interrogans</jats:named-content>strain NR-20157. These included the type of base agar, the concentration of rabbit serum (RS), and the concentration and duration of CO<jats:sub>2</jats:sub>incubation during the initial period of culture. The highest growth rate of NR-20157 was achieved using a Noble agar base supplemented with 10% RS (named LVW agar), with an initial incubation at 30°C in 5% CO<jats:sub>2</jats:sub>for 2 days prior to continuous culture in air at 30°C. These conditions were used to develop the Etest for three species,<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">L. interrogans</jats:named-content>(NR-20161),<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">L. kirschnerii</jats:named-content>(NR-20327), and<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">L. borgpetersenii</jats:named-content>(NR-20151). The MICs were read on day 7 for all samples. The Etest was then performed on 109 isolates of pathogenic<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Leptospira</jats:named-content>spp. The MIC<jats:sub>90</jats:sub>values for penicillin G, doxycycline, cefotaxime, ceftriaxone, and chloramphenicol were 0.64 units/ml and 0.19, 0.047, 0.5, and 2 μg/ml, respectively. The use of LVW agar, which enables rapid growth, isolation of single colonies, and simple antimicrobial susceptibility testing for<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Leptospira</jats:named-content>spp., provides an opportunity for new areas of fundamental and applied research.</jats:p>

Original publication

DOI

10.1128/aac.01812-12

Type

Journal article

Journal

Antimicrobial Agents and Chemotherapy

Publisher

American Society for Microbiology

Publication Date

01/2013

Volume

57

Pages

297 - 302