title: Enzymatic characterization of insecticide resistance mechanisms in field populations of Malaysian Culex quinquefasciatus say (Diptera: Culicidae).
abstract: BACKGROUND
  There 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.
  
  
  RESULTS
  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
  The 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.
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Van Lun
authors.initials: VL
authors.lastname: Low
authors.forename: Chee Dhang
authors.initials: CD
authors.lastname: Chen
authors.forename: Han Lim
authors.initials: HL
authors.lastname: Lee
authors.forename: Tiong Kai
authors.initials: TK
authors.lastname: Tan
authors.forename: Chin Fong
authors.initials: CF
authors.lastname: Chen
authors.forename: Cherng Shii
authors.initials: CS
authors.lastname: Leong
authors.forename: Yvonne Ai Lian
authors.initials: YA
authors.lastname: Lim
authors.forename: Phaik Eem
authors.initials: PE
authors.lastname: Lim
authors.forename: Yusoff
authors.initials: Y
authors.lastname: Norma-Rashid
authors.forename: Mohd
authors.initials: M
authors.lastname: Sofian-Azirun
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism*; D000818:Animals; D003465:Culex / Q000201:enzymology*; D004950:Esterases / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism*; D007305:Insecticide Resistance; D006899:Mixed Function Oxygenases / Q000378:metabolism*
chemical_list: D006899:Mixed Function Oxygenases; D005982:Glutathione Transferase; D004950:Esterases; D000110:Acetylcholinesterase