In vitro efficacy of a buffered chelating solution as an antimicrobial potentiator for antifungal drugs against fungal pathogens obtained from horses with mycotic keratitis.
OBJECTIVE
To determine whether a novel third-generation chelating agent (8 mM disodium EDTA dehydrate and 20 mM 2-amino-2-hydroxymethyl-1, 3-propanediol) would act as an antimicrobial potentiator to enhance in vitro activity of antifungal medications against fungal isolates obtained from horses with mycotic keratitis.


METHODS
Fungal isolates (3 Aspergillus isolates, 5 Fusarium isolates, 1 Penicillium isolate, 1 Cladosporium isolate, and 1 Curvularia isolate) obtained from horses with mycotic keratitis and 2 quality-control strains obtained from the American Type Culture Collection (ATCC; Candida albicans ATCC 90028 and Paecilomyces variotii ATCC 36257).


METHODS
Minimum inhibitory concentrations (MICs) against fungal isolates for 4 antifungal drugs (miconazole, ketoconazole, itraconazole, and natamycin) were compared with MICs against fungal isolates for the combinations of each of the 4 antifungal drugs and the chelating agent. The Clinical and Laboratory Standards Institute microdilution assay method was performed by use of reference-grade antifungal powders against the fungal isolates and quality-control strains of fungi.


RESULTS
Values for the MIC at which the antifungal drugs decreased the growth of an organism by 50% (MIC50) and 90% (MIC90) were decreased for the control strains and ophthalmic fungal isolates by 50% to 100% when the drugs were used in combination with the chelating agent at a concentration of up to 540 microg/mL.


CONCLUSIONS
The chelating agent increased in vitro activity of antifungal drugs against common fungal pathogens isolated from eyes of horses with mycotic keratitis.
Weinstein
William L
WL
Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
Moore
Phillip A
PA
Sanchez
Susan
S
Dietrich
Ursula M
UM
Wooley
Richard E
RE
Ritchie
Branson W
BW
D000818:Animals; D000935:Antifungal Agents / Q000627:therapeutic use*; D002614:Chelating Agents / Q000627:therapeutic use*; D004357:Drug Synergism; D006734:Horse Diseases / Q000188:drug therapy* / Q000382:microbiology*; D006736:Horses; D017964:Itraconazole / Q000627:therapeutic use; D007634:Keratitis / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D007654:Ketoconazole / Q000627:therapeutic use; D008825:Miconazole / Q000627:therapeutic use; D009181:Mycoses / Q000188:drug therapy / Q000662:veterinary*; D010866:Natamycin / Q000627:therapeutic use; D012996:Solutions
D000935:Antifungal Agents; D002614:Chelating Agents; D012996:Solutions; D017964:Itraconazole; D008825:Miconazole; D010866:Natamycin; D007654:Ketoconazole