Characteristics of Houseflies Selected by Fenitrothion and Diethyl Fenitrothion

Abstract

The organophosphate (OP)-resistant Daisan Yumenoshima (3-Y_M) housefly strain, which had been reared under the pressure of malathion, was further selected by fenitrothion (3-Y_F) and by diethyl fenitrothion (3-Y_E). The 3-Y_F and 3-Y_E selected strains were highly resistant to the chemical used in the selection, and their acetylcholinesterases were insensitive to the corresponding OP-oxon. The 3-Y_F and 3-Y_M strains had a high activity for glutathione (GSH)-dependent degradation of fenitrothion, whereas that of the 3-Y_E strain was lower. Salithion was relatively effective against both the 3-Y_F and 3-Y_E strains as well as against 3-Y_M. K-1 and K-2, salioxon analogs as the inhibitors of malathion carboxylesterase, were synergistic with fenitrothion against these strains by inhibiting GSH-dependent detoxication.