The Influnce Of Morphology And Antifungal Susceptibility Of T.asahii After In-vivo Passage And In-vitro Induction

Objective:(1). To investigate the diffrence about morphology and drug susceptibilities of T.asahii between pre- and postpassage in vivo, pre- and postinduct after fluconazole induction in vitro;(2). To observe the isolates’ change of fluconazole MIC,which islated from T.asahii infection model received fluconazole intervention.Methods:(1). Clinical isolates CBS2479 and environmental isolates CBS8904 were respectively and serially in potato dextrose agar medium containing incresing concentrations of fluconazole. Until the MICs is greater than 256ug/ml, Changes in morphology and MIC of the induced isolates were observed.;(2). T.asahii as the object of study, which were five passaged through murine hosts,pre- and postpassage isolates were characterized for there morphology including the shape of colonies by the naked eye and cell types under the microscope, and the minimum inhibitory concentration(MIC) to fluconazole. The MICs of fluconazole the strain used in this study were determined by the broth microdilution method, according to document M27-A3 of the CLSI;(3). 4 strain T.asahii infection model of mice were received fluconazole intervene interruptly and continuously. Isolates’ MICs of fluconazole were after 50 days’ determination of fluconazole.Results:(1). Clinical strains of CBS2479 and environmental strains of CBS8904 after 18 days, 9 generations of fluconazole induction in vitro, there MICs reached to more than256ug/ml from the respectively parent of 1.0ug/ml and 2.0ug/ml, increased 8-32 times.After vitro induction, clinical strains colony surface wrinkle reduction and small, colony edge folds away, as a smooth shape, the morphology of the cells appeared more spores than before; the environmental strains colony central sulcus disappeared, appear more gritty bulge, cells had no significant morphological changes.(2). T.asahii CBS2479/CBS8904/CBS8520/CBS7137 respectively passaged through mice after 50 days, 5 generation, the fluconazole MIC rised from 1.0/2.0/1.0/0.5ug/ml to16.0/4.0/4.0/4.0ug/ml, increased 2-16 times then the corresponding parent strains. The highest growth is clinical isolates T.asahii CBS2479, up to 16ug/ml. Passaged clinical strains changed their colony morphology reduced central sulcus and growed more wrinkles in edge. But the morphology of the cells had no obvious change with hyphae dominated; the colony surface form more folds of the passaged environmental isolates and forming hypha easierly in cells tructures;(3). Passaged strains, which intermittent drug exposure after 50 days of 5 times in vivo, the MICs of T.asahii CBS2479/CBS8904/CBS8520/CBS7137 rised from1.0/2.0/1.0/0.5ug/ml to 32.0/16.0/16.0/16.0ug/ml, increased 8-32 times. The MICs reached to 164.0/16.0/32.0/32.0ug/ml, growthed 16-64 times after continuous drug exposure subculture, which significantly increased then the isolates naturely passaged in vivo. Compared with Intermittent treatment, continuous treatment group fluconazole MICs increased more.Conclusion:Morphogenesis and drug susceptibilities to fluconazole of T.asahii are changed by in-vivo passage and in-vitro induction. After in-vivo passage, the morphogenesis of environmental isolates has the transitional trend to clinical isolates, which is contrary with in-vitro induction. Both in vivo passage and in vitro induction, the fluconazole MICincreased with the clinical isolates is more significant than environmental isolates. The fluconazole MIC level of growth in-vitro induction is higher and faster than in-vivo passage.