Pyrethroid-treated bed nets and indoor spray are important components of malaria control strategies in Kenya. Information on resistance to pyrethroid insecticides in Anopheles gambiae and An. arabiensis populations is essential to the selection of appropriate insecticides and the management of insecticide resistance. Monooxygenase activity and knockdown resistance (kdr) allele frequency are biochemical and molecular indicators of mosquito resistance to pyrethroids. This study determined baseline information on monooxygenase activity and kdr allele frequency in anopheline mosquitoes in the western region, the Great Rift Valley-central province region, and the coastal region of Kenya. A total of 1990 field-collected individuals, representing 12 An. gambiae and 22 An. arabiensis populations was analyzed. We found significant among-population variation in monooxygenase activity in An. gambiae and An. arabiensis and substantial variability among individuals within populations. Nine out of 12 An. gambiae populations exhibited significantly higher average monooxygenase activity than the susceptible Kisumu reference strain. The kdr alleles (L1014S) were detected in three An. gambiae populations, and one An. arabiensis population in western Kenya, but not in the Rift Valley-central region and the coastal Kenya region. All genotypes with the kdr alleles were heterozygous, and the conservative estimation of kdr allele frequency was below 1% in these four populations. Information on monooxygenase activity and kdr allele frequency reported in this study provided baseline data for monitoring insecticide resistance changes in Kenya during the era when large-scale insecticide-treated bednet and indoor residual spray campaigns were being implemented.

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21089 Background: Genotyping of clinical samples has been limited to low levels of multiplexing, ranging from one to a few dozen single nucleotide polymorphisms (SNPs) per sample. By increasing multiplexing levels, a clinical lab can increase information content per sample, decreasing costs and sample material requirements. Methods: We have adapted the GoldenGate® Assay for simultaneously genotyping 96 to 1,536 SNPs to the BeadXpress™ System, a new high-throughput platform that utilizes digitally inscribed VeraCode™ beads in a compact fluidic instrument. Genotyping on this platform ranges from 96 to 384 multiplexing, using the same GoldenGate Assay that has proven highly robust for millions of genotypes. In preliminary tests, we have observed greater than 99% call rates, and greater than 99.5% rates for reproducibility and heritability. In a test of 96 SNP genotypes chosen for a study of colorectal cancer, a point mutation in the MSH2 gene, previously implicated in predisposition to several cancers, was correctly genotyped when compared to qPCR analysis of the same samples. Conclusion: Together with genotyping data from reference samples, the GoldenGate Assay on the BeadXpress System has yielded highly reproducible and accurate genotypes, suggesting that this approach will prove useful for rapid refinement of SNPs for development of clinical genotyping tests. No significant financial relationships to disclose.

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