Objectives: Acanthamoeba spp. are causative agents of granulomatous amoebic encephalitis, and more frequently of keratitis, in the case of minor corneal surface injury caused by contact lens or other agents. The effective therapy for these pathologies has to be improved and new drugs are needed, particularly when a resistance to classical therapeutics is encountered. Some azoles or other antifungals have already been used in different clinical situations. We evaluated here the effect of caspofungin, a new antifungal belonging to the echinocandins, on trophozoites and cysts of three strains of Acanthamoeba. Methods: Trophozoites and cysts of A. castellani (ATCC 30234), A. polyphaga (ATCC 30461), and A. culbertsoni (ATCC 30171) were exposed to solutions of 500 μg/ml to 16 μg/ml of caspofungin for 1, 4 and 24 h (trophozoites) and 24, 48 and 72 h (cysts). The viability of trophozoites was then determined by the toluidine blue staining. The cystic forms were resuspended after contact with caspofungin in a medium allowing the viable microorganisms to excyst. Replication of the subsequent trophozoites was observed microscopically during 7 days. Each experiment was repeated three times. Results: The activity of caspofungin on the trophozoites' growth was dependant of the tested concentration. At the concentration of 16 μg/ml, the viability of trophozoites was reduced of 5 (A. castellanii) to 60% (A. polyphaga). At the concentration of 500 μg/ml, we observed no viability of the trophozoites for the three tested strains. The cysts of A. castellanii and A. polyphaga were sensitive to the concentration of 500 μg/ml of caspofungin. As a matter of fact, no trophozoite was recovered after 7 days of incubation. Then, the percentage of viable forms increased when the concentration of caspofungin decreased. Concerning A. culbertsoni, the highest concentration used in this study did not prevent the excystation of a weak percentage of the treated cysts forms. Conclusion: Our results indicated that caspofungin showed in vitro activity against trophozoites and cysts stages of the tested Acanthamoeba strains. This new antimicrobial agent could be promising to treat, alone or in association, Acanthamoeba keratitis.
Full conference title:
16th European Congress of Clinical Microbiology and Infectious Diseases
- ECCMID 16th (2006)