Antimicrobial Efficacy against Acanthamoeba Isolates from Clinical Cases.

Introduction: Acanthamoeba spp. are free-living protozoan parasites that can cause painful, severe ocular inflammation and sight-threatening keratitis. Acanthamoeba keratitis is a widespread infectious corneal disease that has been reported worldwide. Objective: This study investigates the effectiveness and the range of minimum cysticidal concentration (MCC) of four antimicrobial agents in therapeutic doses; 0.02% chlorhexidine, 0.1% propamidine isethionate (Brolene®), 0.3% ciprofloxacin and 0.3% gentamicin against 4 clinical isolates of Acanthamoeba. Four isolates of Acanthamoeba cysts being used were derived from clinical cases (HKL 95, HKL 109, HS 5 and HS 6). Materials and methods: Serial doubling dilutions of the antimicrobial agents were performed in microtiter plates. After exposure of the four Acanthamoeba isolate cysts to the four antimicrobial agents for 24 hours, the cysts were washed three times with PAS and centrifuged. The deposits (cysts) were cultured onto non-nutrient agar coated with heat-killed Escherichia coli. The excystment of trophozoites from cysts was observed and recorded microscopically for 14 days to determine the MCC value of each drug. Results: Results of this study showed that chlorhexidine, propamidine isethionate, ciprofloxacin and gentamicin successfully exhibited their cysticidal activities in therapeutic doses on all isolates. The values of MCC for chlorhexidine, propamidine isethionate, ciprofloxacin and gentamicin varied from 6.25 to 25 pg/ml, 125 to 250 pg/ml, 1500 to 3000 pg/mi and 1500 to 3000 pg/ml, respectively. Moreover, chlorhexidine, propamidine isethionate, ciprofloxacin and gentamicin were found to exhibit cysticidal activities with their mean MCC values of 17.2 ± 9.4 pg/ml, 156.3 ± 62.5 pg/ml, 2625 ± 750 pg/ml and 1875 ± 750 pg/ml, respectively. Conclusion: The in vitro sensitivity test can be used as a standard test to determine values of MCC of drugs on Acanthamoeba isolates and to study the susceptibility pattern of anti-Acanthamoeba drugs. Chlorhexidine and Propamidine isethionate exhibited the best anti-Acanthamoeba activity and are therefore highly recommended for use in the treatment of Acanthamoeba keratitis. [ABSTRACT FROM AUTHOR]