Purpose: In Aspergillus fumigatus, Mechanisms for azole-drugs resistance have been investigated about mutation of CYP51A. But, there are still azole resistant strains that were not known the resistance mechanism. These suggest that no mutation has been introduced in CYP51A, and a new resistance factor is present. In the previous study of our group, we obtained results suggesting that mutation of HMG-CoA reductase (HMG1), the rate-limiting enzyme in ergosterol biosynthesis, is mechanism conferring azole-drugs resistance. The aim of this study is clarifying the role of SNP in hmg1 for the azole resistance mechanism.
Methods: It was investigated whether the azole-drugs resistance clinical strains without any mutation in CYP51A (non-cyp51A resistant strains) possess mutations in hmg1 gene. The phenotypes associated with ergosterol biosynthesis were examined in non-cyp51A resistant strain (hmg1 mutation azole resistant strain).
Results: The mutations in hmg1 were a found in other non-cyp51A azole resistant strains. These results suggested a close link between azole resistance and the SNP in hmg1 gene. Disk diffusion assay showed that the hmg1 mutation azole resistant strain was more sensitive to polyene drugs, suggesting that ergosterol production might be differentially regulated. Interestingly, hmg1 mutation azole resistant strain showed increased sensitivity to lovastatin that is an inhibitor for HMG-CoA reductase. The ergosterol content in the cells was measured by HPLC, showing significant increase in the hmg1 mutation azole resistant strain.
Conclusion: It was strongly suggested that mutation of hmg1 is involved in azole resistance mechanism. The phenotypes associated with ergosterol biosynthesis was different between hmg1 mutation azole resistant strain and susceptible strain (Wild type). This phenotypic difference was considered to be related to resistance mechanism. Genetic transformation test for clarifying the role of SNP in hmg1 is underway.
Full conference title:
- AAA 8th (2018)