Inhibitory effect of housefly antimicrobial peptide AMP-17 on hyphae of Candida albicans

Abstract:

[Background] AMP-17 is a specific and highly expressed gene screened from the database of housefly transcriptional group induced by microorganisms. Its recombinant AMP-17 protein was obtained by utilizing the prokaryotic expression system and proved to have significant antimicrobial effect, especially for Candida albicans. [Objective] To investigate the inhibitory effect of AMP-17 on the hyphae of Candida albicans. [Methods] The minimum inhibitory concentration (MIC) of AMP-17 on 11 strains of Candida albicans were determined by microdilution method; Three strains of Candida albicans were selected to plot the growth curve according to their sensitivity to AMP-17; The blastospore production rate and germ tube formation rate of Candida albicans after AMP-17 were observed and counted by optical microscope; The transformation of Candida albicans yeast phase to mycelial phase and AMP-17 promoted the transformation of mycelial phase into yeast phase with mycelial phase as the starting point were observed by fluorescent inverted microscope. [Results] The MIC of AMP-17 to the strain isolated from BALF 16105 was 10 μg/mL, the MIC to the strain isolated from fecal 16214 was 40 μg/mL, and the MIC to the other 9 strains of Candida albicans were 20 μg/mL. After the action of AMP-17 at different concentrations, the rate of blastospore formation at each time point was significantly lower than that of the control group, especially in the AMP-17 group of 40 μg/mL, the rate of blastospore formation was only 15%, obviously lower than that of fluconazole, a positive drug. The rate of germ tube formation in each experimental group were obviously lower than that in the control group, and the germ tube formation was slow. After 6 h of culture, the germ tube formation rate was only 6%, and the germ tube was short, which was only 1?2 times of thallus. Low concentration of AMP-17 could completely inhibit the growth of Candida albicans hyphae, and inhibit the growth of already formed hyphae to some extent, while high concentration of AMP-17 could transform some formed hyphae into yeast phase by microscopes. [Conclusion] Housefly antimicrobial peptide AMP-17 can inhibit the growth of Candida albicans hyphae.

Key words:Candida albicans, Antimicrobial peptide, Hyphae