Molecular cloning and heterologous expression of a glutathione S-transferase involved in insecticide resistance from the diamondback moth, Plutella xylostella

Five Culex pipiens samples were collected at preimaginal stages from breeding sites in 5 localities of Grand Tunis area, Northeast Tunisia, between March 2002 and November 2005. Larvae were used for bioassays using ethanol solutions of chlorpyrifos and propoxur insecticides. All samples were resistant to chlorpyrifos (RR>1, p<0.05). The highest resistance levels (>1,000-fold) were recorded in samples # 2, 4, and 5. Our synergist study showed that the increased detoxification by EST (and/or GST) had only a minor role in the chlorpyrifos resistance, although several overproduced esterases, known to be involved in the OPs resistance, were detected in all the resistant field samples. The mortality due to propoxur was significantly correlated with the LC 50 of chlorpyrifos and indicated an insensitive AChE.

Section: Discussioncontrasting

confidence: 84%

Evaluation of Chlorpyrifos Resistance and Biochemical Mechanisms of Culex pipiens in Five Localities of Grand Tunis Area, Northeast Tunisia

Daaboub¹,

Tabbabi²,

Lamari³

et al. 2017

“…This confirms the hypothesis that somes esterases, GSTs, and cytochrome P450 enzymes may be insensitive to the action of DEF and Pb. The involvement of EST and the GST in the OPs resistance was confirmed by many previous studies [2,3,[25][26][27][28][29][30][31][32]. Our study is in agreement with previous publication on correlation between cytochrome P450 enzymes and resistance to pyrethroids [33].…”

Section: Discussionsupporting

confidence: 93%

Study on Resistance of Culex pipiens (Diptera: Culicidae) Populations to Fenitrothion in Northern Tunisia

Tabbabi¹,

Daaboub²,

Cheikh³

et al. 2017

Four populations of Culex pipiens were collected as larvae in Northern Tunisia to evaluate their resistance status against two insecticides: fenitrothion and propoxur. At LC50, the sample # 1 was susceptible, whereas all the other samples were resistant. The RR50 ranged from 1.08 in sample # 1 to 550 in sample # 3. The A2-B2, A4-B4 (and/or A5-B5), B12 and C1 esterases were found in collected samples and the frequencies ranged from 0.02 to 0.42. Propoxur caused a mortality of 0% in samples # 3 which showed the highest resistance levels to fenitrothion insecticide and 87% in sample # 1 which was susceptible hence the involvement of AChE 1 in the recorded resistance. Our results are essential for the development of such strategies of vector control.

“…Our and previous study confirmed the presence of stronger esterase activity in the most resistant chlorpyrifos samples (samples # 1 and 2) [8,18,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. The esterase activity is very variable between individuals of the same sample, as evidenced by the results observed on single individuals after starch gel electrophoresis of the extracts, but it is clear that the proportion of individuals with high esterase activity is more important in samples where resistance is high.…”

Section: Discussionsupporting

confidence: 86%

Susceptibility of Larval Stage of Mosquito Culex pipiens against Chlorpyrifos Insecticide in Southern Tunisia

Daaboub¹,

Tabbabi²,

Cheikh³

et al. 2017

Three populations of mosquito Culex pipiens were used to study the susceptibility of larval stage against organophosphate chlorpyrifos and carbamate propoxur insecticides in Southern Tunisia. All samples were resistant to chlorpyrifos (RR>1, p<0.05) and the tolerance to this insecticide was varied between 1.8 and 1318. The sample # 3 was the most susceptible and disclosed a little difference when compared to S-Lab (RR50=1.9). The highest resistance levels (>1,000-fold) was recorded in samples # 2 (South East). The level of resistance was lower, not exceeding 2-fold in samples # 3 (Far South). Total esterase activity of field populations detected one or several esterases in all the studied samples, with the exception of the sample # 3 despite the addition of DEF showed that the increased detoxification by EST and/or GST was not responsible for chlorpyrifos resistance in these samples. Oxidative metabolism accounted for only a small part of the observed resistances because chlorpyrifos resistance ratios remained high in the presence of the Pb. The mortality due to propoxur was significantly correlated with the LC50 of chlorpyrifos and indicated an insensitive AChE in samples # 2 which showed the highest resistance levels to chlorpyrifos insecticide (1%). Results were discussed in relation to resistance mechanisms and Culex pipiens control.