Mechanism of trifluoromethionine resistance in Entamoeba histolytica

Objectives: To determine the mechanism of trifluoromethionine resistance in Entamoeba histolytica and evaluate the impact of acquired drug resistance on virulence. Methods: Trifluoromethionine-resistant amoebae were selected in vitro and examined for cross-resistance to antiamoebic drugs, stability of resistance, methionine gamma-lyase (MGL) activity, cell adhesion and virulence. Targeted gene silencing was performed to confirm the role of EhMGL. Results: Trophozoites with a resistance index of 154 were obtained. The cells were susceptible to chloroquine, metronidazole, paromomycin and tinidazole, but remained resistant to trifluoromethionine in the absence of drug pressure. A complete lack of EhMGL activity accompanied by increased adhesion and decreased cytolysis were also observed. Silencing of the EhMGL genes resulted in trifluoromethionine resistance. Conclusions: This study provides the first demonstration of trifluoromethionine resistance in a parasitic protozoon. Repression of gene expression of drug targets represents a novel mechanism of resistance in E. histolytica. The information obtained from this work should help further development of trifluoromethionine derivatives that have lower chances of inducing resistance.