Tehran University of Medical Sciences Journal of Arthropod-Borne Diseases 2322-1984 12 4 2018 10 12 370 377 Onur Guntay Section of Molecular Biology, Department of Biology, Faculty of Science, Ege University, Turkey Mehmet Salih Yikilmaz Section of Molecular Biology, Department of Biology, Faculty of Science, Ege University, Turkey Huseyin Ozaydin Section of Molecular Biology, Department of Biology, Faculty of Science, Ege University, Turkey Savas Izzetoglu Section of Molecular Biology, Department of Biology, Faculty of Science, Ege University, Turkey Asli Suner Department of Biostatistics and Medical Informatics, Faculty of Medicine, Ege University, Turkey 2018 12 10 Background: Mosquitoes, being a nuisance species, are considered as one of the most important species in public health control programs due to their role as a vector in mosquito-borne diseases observed in humans and animals. We evaluated the susceptibility status of Culex pipiens collected from northern Izmir, Turkey in 2011-16. Methods: Mosquito larvae, collected from three different locations in northern İzmir, were reared in the laboratory. Adult susceptibility bioassays were performed using the WHO insecticide-impregnated papers including deltamethrin 0.05%, permethrin 0.75%, α-cypermethrin 0.05% and cyfluthrin 0.15%. In addition, adult bioassays were performed after the pre-exposure to piperonyl butoxide (PBO) to determine the contribution of P450 detoxification enzymes to the phenotypic resistance. Results: In all of the three populations, high levels of resistance were observed (mortalities<63%) to all of the four pyrethroids. Different pyrethroids but with the same mode of action can exhibit significantly different phenotypic re­sistance in a single population. PBO bioassays also showed that P450 detoxification enzymes can have diverse effects on different pyrethroids. Conclusion: Using just one chemical in a class of insecticide can be misleading for resistance studies. https://jad.tums.ac.ir/index.php/jad/article/view/1026 https://jad.tums.ac.ir/index.php/jad/article/download/1026/424