Antimicrobial susceptibility of 19 Australian corneal isolates of Acanthamoeba.
OBJECTIVE
To determine the in vitro drug susceptibility of Australian corneal isolates of Acanthamoeba and to correlate the results with patient treatment and visual outcome.


METHODS
Acanthomoeba isolates were obtained from a reference laboratory Cyst suspensions were prepared from 19 strains and exposed to 10 antimicrobial agents for 7 days. The minimum drug concentrations required to inhibit excystation were determined. Inhibited cells were then plated out to determine minimum cysticidal concentrations.


RESULTS
Overall, propamidine proved to be the most active anti-Acanthamoeba agent tested. The disinfectant polyhexamethylene biguanide, either pure or in Baquacil, was also effective. Pentamidine, hexamidine, chlorhexidine and chloroxylenol had intermediate activity, while neomycin, amphotericin B and povidone-iodine had poor activity. There was no clear relationship between in vitro susceptibility and visual outcome.


CONCLUSIONS
Propamidine and polyhexamethylene biguanide drops are recommended as initial choices for the treatment of Acanthamoeba keratitis. The variability in the susceptibility to any one agent suggests that individual testing of isolates is necessary to identify the most appropriate treatment. A number of factors influence visual outcome in these cases; further studies are required to resolve the importance or otherwise of in vitro susceptibility.
Department of Ophthalmology, Flinders University of South Australia, Bedford Park, Australia.
L
L
Lim
D J
DJ
Coster
P R
PR
Badenoch
D000048:Acanthamoeba / Q000187:drug effects* / Q000302:isolation & purification; D015823:Acanthamoeba Keratitis / Q000188:drug therapy / Q000469:parasitology; D000328:Adult; D000818:Animals; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D004202:Disinfectants / Q000494:pharmacology*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D021261:Parasitic Sensitivity Tests
D000891:Anti-Infective Agents, Local; D000981:Antiprotozoal Agents; D004202:Disinfectants; D009883:Ophthalmic Solutions