<Emphasis Type="Italic">Ochroconis calidifluminalis</Emphasis>, a Sibling of the Neurotropic Pathogen <Emphasis Type="Italic">O. gallopava</Emphasis>, Isolated from Hot Spring |
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Authors: | Kyoko Yarita Ayako Sano Kittipan Samerpitak Katsuhiko Kamei G Sybren de Hoog Kazuko Nishimura |
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Institution: | (1) Medical Mycology Research Center (MMRC), Chiba University, Chiba, Japan;(2) Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand;(3) CBS-KNAW Fungal Biodiversity Centre, Utrecht, The Netherlands;(4) Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, The Netherlands;(5) Research Center for Medical Mycology, Peking University Health Science Center, Beijing, China;(6) First Laboratories Co. Ltd., Chiba, Japan |
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Abstract: | Two strains resembling the neurotropic fungus Ochroconis gallopava were isolated from hot spring river water (IFM 54738 and IFM 54739). The isolates showed optimal growth at 42°C, while the
maximum growth temperature was 49°C, thus having temperature relationships similar to those of O. gallopava. Colonies were light olive green, with a color change to dark reddish brown after several passages, which was also observed
in O. gallopava. Conidia were indistinguishable from those of O. gallopava. The antifungal susceptibility profile of the isolates was also similar to that of O. gallopava, except for a lower susceptibility to micafungin. The two isolates had 100% homologous rRNA genes including the internal
transcribed spacer (ITS) region and the D1/D2 region of the large subunit. The gene fragments, as O. gallopava, could be amplified with species-specific rDNA primers, and loop-mediated isothermal amplification designed for O. gallopava yielded positive results in the two isolates. However, homologies with O. gallopava in ITS and D1/D2 regions were 79.2 and 95.9%, respectively, widely exceeding generally accepted species boundaries. These
differences were corroborated in virulence tested in experimental infection. The two isolates did not kill a mouse even until
28 days. However, mortalities of four O. gallopava strains ranged from 40 to 100%. The new isolates mainly affected the kidneys; whereas O. gallopava had a strong preference for the brain. We therefore propose a new species, Ochroconis calidifluminalis, for the two isolates. |
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