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.
Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
William L
WL
Weinstein
Phillip A
PA
Moore
Susan
S
Sanchez
Ursula M
UM
Dietrich
Richard E
RE
Wooley
Branson W
BW
Ritchie
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