Mutants with heteroresistance to amphotericin B and fluconazole in Candida

Several studies have reported the occurrence of infections caused by Candida yeasts as well as the increasing prevalence of non albicans species. The aim of the present work is focused on the obtaining of heteroresistance to amphotericin B and fluconazole in Candida species using two distinct methodologies: selection and induction. Resistant samples were obtained by selective pressure using a medium with fluconazole for growth, followed by growth in a medium with amphotericin B. The selective pressure was also created beginning with growth in amphotericin B medium followed by growth in fluconazole medium. Concomitantly, samples were submitted to the induction of resistance through cultivation in increasing concentrations of fluconazole, followed by cultivation in increasing concentrations of amphotericin B. Subsequently, the induction began with amphotericin B followed by fluconazole. Three samples resistant to fluconazole and amphotericin B were obtained, two by induction (C. glabrata and C. tropicalis) and one by selection (C. tropicalis). Both C. tropicalis originated from the same wild sample. After successive transfers for drug free medium, only the sample obtained by selection was able to maintain the resistance phenotype. These results suggest that the phenotype of heteroresitance to fluconazole and amphotericin B can be produced by two methodologies: selection and induction.

Study on Breeding of High-yield Avilamycin-producing Strains by Nitrogen Ion Implantation / 微生物学通报

To obtain high-yield avilamycin-producing strains,low energy N~+ ion implantation technology and screening of streptomycin-re- sistant mutants are used in the study on breeding mutation.The results show that,“saddle”region,which range is from 3?10~(15) to 5?10~(15) ions/cm~2,has got better induced mutation action.It also means that the strain's resistant mutation and yield mutation closely correlate to each other,and the method of streptomycin resistant screening is feasible.We have isolated a high-yield strain SVT-45 which the productivi- ty is 195% higher than the original strain's in the rotation-flask experiments.These results showed that the ion implantation was an effective method for microbe mutagensis.