Evaluation of the sensitivity to chlorhexidine, voriconazole and itraconazole of T4 genotype Acanthamoeba isolated from Mexico.

Free-living amoebae of the genus Acanthamoeba are the etiological agents of cutaneous lesions, granulomatous amoebic encephalitis (GAE) and amoebic keratitis (AK), which are chronic infections with poor prognosis if not diagnosed promptly. Currently, there is no optimal therapeutic scheme to eradicate the pathologies these protozoa cause. In this study we report the morphological and molecular identification of three species of the genus Acanthamoeba, belonging to T4 group; A. polyphaga isolated from the corneal ulcer of a patient sample of AK case; A. castellanii isolated from the contact lens of an AK patient and A. palestinensis obtained from a soil sample. The in vitro activity of chlorhexidine, itraconazole and voriconazole drugs against trophic stage was also evaluated through a colorimetric assay based on the oxidation-reduction of alamar blue. The strains in the study were sensitive to the evaluated drugs; although when determining the 50% inhibitory concentration (IC50) statistically significant differences were observed. A. castellanii showed to be highly sensitive to voriconazole (0.66 ± 0.13 μM) but the least sensitive to chlorhexidine and itraconazole (8.61 ± 1.63 and 20.14 ± 4.93 μM, respectively), A. palestinensis showed the highest sensitivity to itraconazole (0.502 ± 0.11 μM) and A. polyphaga expressed moderate sensitivity to chlorhexidine and itraconazole and lower sensitivity to voriconazole (10.10 ± 2.21 μM). These results showed that species of the genus Acanthamoeba express different sensitivity to the tested drugs, which could explain the problems surrounding the establishment of a treatment of choice in the infections caused by these amoebae. We consider that although chlorhexidine and itraconazole show good activity on these amoebae and have been used in cases of AK in Mexico with acceptable results, voriconazole should be considered as the first therapeutic option of future Acanthamoeba infections that will be diagnosed in our country.