To examine the hydrolytic metabolism and related resistance of housefly Musca domestica (M. domestica) to malathion, differences in the hydrolytic metabolic abilities between malathion-susceptible and malathion-resistant M. domestica were examined using gas chromatography with nitrogen-phosphorus detector (GC-NPD). After incubation of M. domestica abdomen homogenates with malathion, the malathion residue was quantitatively determined by GC-NPD after extraction with a mixture of ethyl acetate and n-hexane at 2:1 (v/v). The hydrolytic metabolic abilities of M. domestica to malathion were then characterized. By comparing the differences in hydrolytic abilities between malathion-susceptible and malathion-resistant M. domestica, it was found that the hydrolytic abilities of malathion-resistant M. domestica were 6.68-fold than that of malathion-susceptible M. domestica, while the hydrolytic abilities toward α-naphthyl acetate were 1.39-fold. Resistance to malathion is related to the enhanced hydrolytic metabolism of malathion by M. domestica. Further understanding of the metabolic resistance mechanism will assist in developing a management strategy for malathion-resistant M. domestica. This method could be used for studying the metabolic ability and related resistance of M. domestica toward malathion.
Keywords: Musca domestica; gas chromatography with nitrogen-phosphorus detector (GC-NPD); malathion; metabolic resistance.