ABSTRACT
BACKGROUND: Three de novo designed low molecular weight cationic peptides (IJ2, IJ3 and IJ4) containing an unnatural amino acid α,ß-didehydrophenylalanine (∆Phe) exhibited potent antifungal activity against fluconazole (FLC) sensitive and resistant clinical isolates of Candida albicans as well as non-albicans and other yeast and filamentous pathogenic fungi. In the present study, their synthesis, susceptibility of different fungi and the mechanism of anti-candidal action have been elucidated. METHODS: The antimicrobial peptides (AMPs) were synthesized by solid-phase method and checked for antifungal activity against different yeasts and fungi by broth microdilution method. Anti-candidal mode of action of the peptides was investigated through detecting membrane permeabilization by confocal microscopy, Reactive Oxygen Species (ROS) generation by fluorometry, apoptosis and necrosis by flow cytometry and cell wall damage using Scanning and Transmission Electron Microscopy. RESULTS AND CONCLUSIONS: The MIC of the peptides against C. albicans and other yeast and filamentous fungal pathogens ranged between 3.91 and 250µM. All three peptides exhibited effect on multiple targets in C. albicans including disruption of cell wall structures, compromised cell membrane permeability leading to their enhanced entry into the cells, accumulation of ROS and induction of apoptosis. The peptides also showed synergistic effect when used in combination with fluconazole (FLC) and caspofungin (CAS) against C. albicans. GENERAL SIGNIFICANCE: The study suggests that the AMPs alone or in combination with conventional antifungals hold promise for the control of fungal pathogens, and need to be further explored for treatment of fungal infections.
Subject(s)
Antifungal Agents/chemical synthesis , Antifungal Agents/pharmacology , Candida albicans/drug effects , Peptides/chemical synthesis , Peptides/pharmacology , Apoptosis/drug effects , Caspofungin , Cell Membrane Permeability/drug effects , Cell Wall/drug effects , Cell Wall/metabolism , Drug Synergism , Echinocandins/pharmacology , Fluconazole/pharmacology , Hemolysis/drug effects , Lipopeptides , Necrosis/drug therapy , Necrosis/metabolism , Reactive Oxygen Species/metabolismABSTRACT
Objective To test the in vitro activity of azithromycin against recent clinical isolates of urogenital Chlamydia trachomatis, and combined activity of azithromycin with moxifloxacin, rifampicin, doxycycline and minocyline. Methods When more than 90% McCoy cells were infected, the 41 strains tested were collected to investigate minimal inhibitory concentrations (MICs) of 5 antimicrobials alone. Checkerboard array was used to calculate the fractional inhibitory concentrations(FICs) and then detected the interactions among the various combinations. Results In vitro, synergism or additivity effect of 51.22%,53.66% and 58.54% strains was found in azithromycin-moxifloxacin, azithromycin-doxycycline and asithromycin-rifampicin combinations, respectively. No difference was observed in all of the combinations ( P ＞0.05). However, antagonism effect of 90.24% strains was observed in azithromycin-minocyline combination. Conclusion This study indicates that the combination of azithromycin with moxifloxacin, doxycycline or rifampicin is more effective against Chlamydia trachomatis than individual antimicrobials. Therefore, these antimicrobials combinations might be recommended against Chlamydia trachomatis recurrent or persisitent infection. However, the combination of azithromycin with minocyline exhibited a markedly antagonism activity against Chlamydia trachomatis. Combined sensitivity test to a certain extent can compensate for some shortcomings of individual susceptibility test.
