Level of Pyrethroid-resistance Associated with Cytochrome P450 Expression in German Cockroach Blattella germanica (Blattodea: Ectobiidae) in the Field Collected Strains

Abstract

Background: Cytochrome P450-dependent monooxygenases are a very important metabolic system involve in insecti­cide resistance. This study was conducted to find the association between the expression level of cytochrome P450 (CYP450) and permethrin-resistance level among four strains of the German cockroach Blattella germanica (L) (Blat­todea: Ectobiidae). Methods: Three field strains of German cockroach with different frequency of exposure to pesticides, and a laboratory susceptible strain were used in the present study. Insecticide susceptibility bioassays were carried out to detect re­sistance to permethrin. The concentration of CYP450 in each strain was determined using ion-exchange HPLC chroma­tography. Biochemical assays was performed to analyse CYP450 activities. Results: The resistance ratios (RR) to permethrin among three field strains were 3.29, 4.10 and 6.17-fold comping with the susceptible stain. The CYP450 activity of three field strains was 1.6, 2.4 and 2.7 times higher than in the sus­ceptible stain. The amount of CYP450 per mg of protein was significantly different between the susceptible and the three re­sistant strains. The resistant cockroaches showed a relatively high expression of CYP450 enzymes. A strong corre­la­tion was found between permethrin resistance level and total concentration of CYP450 enzymes. Conclusion: The results of current study show that more frequent usage of a pyrethroid insecticide cause the metabolic insecticide resistance to rise in German cockroach. Therefore, there is a ratio correlation between resistance level and monooxygenases activities in insect. Thus, the control program must be managed according to history of pesticide us­age.

Keywords

• Cytochrome P450; German cockroach; Insecticide resistance; Permethrin