Enzymatic Characterization of Insecticide Resistance Mechanisms in Field Populations of Malaysian Culex quinquefasciatus Say (Diptera: Culicidae)

Abstract

BackgroundThere has been no comprehensive study on biochemical characterization of insecticide resistance mechanisms in field populations of Malaysian Culex quinquefasciatus. To fill this void in the literature, a nationwide investigation was performed to quantify the enzyme activities, thereby attempting to characterize the potential resistance mechanisms in Cx. quinquefasciatus in residential areas in Malaysia.Methodology/Principal Findings Culex quinquefasciatus from 14 residential areas across 13 states and one federal territory were subjected to esterases, mixed function oxidases, glutathione-S-transferase and insensitive acetylcholinesterase assays. Enzyme assays revealed that α-esterases and β-esterases were elevated in 13 populations and 12 populations, respectively. Nine populations demonstrated elevated levels of mixed function oxidases and glutathione-S-transferase. Acetylcholinesterase was insensitive to propoxur in all 14 populations. Activity of α-esterases associated with malathion resistance was found in the present study. In addition, an association between the activity of α-esterases and β-esterases was also demonstrated.Conclusions/SignificanceThe present study has characterized the potential biochemical mechanisms in contributing towards insecticide resistance in Cx. quinquefasciatus field populations in Malaysia. Identification of mechanisms underlying the insecticide resistance will be beneficial in developing effective mosquito control programs in Malaysia.

Temephos Resistance in Culex quinquefasciatus Population from Pabean Subdistrict Pekalongan

“…Esterase is the detoxification enzyme which involved mainly in insecticide resistance. In Malaysia, Low et al 14 had confirmed by using biochemical tests that a major factor resulting in resistance in Cx. quinquefasciatus was due to elevated levels of esterase which correlated directly with malathion (OP) resistance.…”

Esterase in Imported Fire Ants, Solenopsis invicta and S. richteri (Hymenoptera: Formicidae): Activity, Kinetics and Variation

“…As a critical component in insect's detoxification process, esterase has been intensively investigated in the context of insecticide resistance. Elevated esterase activities are associated with decreased insecticide susceptibility in numerous insects1617181920212223242526. The detoxifying enzymes are important not only in tolerance and resistance of insects to both synthetic and natural toxins, but also in defense against microbial infection.…”

“…Esterase isozymes in insects, particularly those in Drosophila and mosquitoes, are classified according to their preferential hydrolysis of the isomeric artificial substrates, α-naphthyl acetate (α-NA) and β-naphthyl acetate (β-NA)15. Although the classification has little value as a predictor of enzyme function, esterase activities measured using those substrates have often been proven to be associated with insecticide tolerance and resistance1617181920212223242526. In this study, we tested a hypothesis that S. invicta has higher esterase activity than S. richteri .…”

A New Esterase Amplification Involved in OP Resistance in Culex Pipiens Mosquitoes from Tunisia

“…This super-locus is composed of two loci, Est-3 and Est-2, and both loci encode for detoxifying esterase. The resistance mechanism at Ester corresponds to an esterase over-production at one or both loci [2,[3][4][5]. This study was conducted in order to address the following points: what is the resistance status in Tunisia populations of the Culex pipiens with regard to Chlorpyrifos insecticides and which resistance genes are involved?…”