Evaluating the in vitro efficacy of gatifloxacin, levofloxacin and gentamicin against Acanthamoeba cysts.

PURPOSE: To evaluate the in vitro efficacy of three commercial ophthalmic solutions (gatifloxacin, levofloxacin and gentamicin) against cysts of Acanthamoeba species.

DESIGN

Experimental study

METHODS

Acanthamoeba cysts belonging to genotypes T3, T4 and T5 were incubated with three ophthalmic solutions for different periods of time; 1, 24, 48 and 72 h at 37 °C. After incubation, treated cysts were stained with trypan blue and counted to express the percent of growth inhibition. Additionally, the viability of treated cysts was assessed by culturing them in PYG medium at 30 °C for 72 h as well as on non-nutrient agar plates at 30 °C for 1 month.

RESULTS

Acanthamoeba cysts of all genotypes were susceptible to gentamicin and gatifloxacin after exposure for 1 h and 24 h, respectively, and for levofloxacin, cysts of all genotypes were resistant to levofloxacin even after 72 h of incubation. Gentamicin and gatifloxacin showed statistically highly significant difference (P < 0.001), and levofloxacin showed statistically significant difference (P < 0.05) in comparison to non-treated control.

CONCLUSIONS

Gentamicin and gatifloxacin were highly effective against Acanthamoeba cysts. Although our results should be confirmed in animal models, this result will guide the choice of the appropriate ophthalmic drugs for early treatment of eye infection caused by Acanthamoeba spp.