A bioinformatic filter for improved base-call accuracy and polymorphism detection using the Affymetrix GeneChip® whole-genome resequencing platform

DNA resequencing arrays enable rapid acquisition of high-quality sequence data. This technology represents a promising platform for rapid high- resolution genotyping of microorganisms. Tradi- tional array-based resequencing methods have relied on the use of specific PCR-amplified frag- ments from the query samples as hybridization targets. While this specificity in the target DNA population reduces the potential for artifacts caused by cross-hybridization, the subsampling of the query genome limits the sequence coverage that can be obtained and therefore reduces the techni- que's resolution as a genotyping method. We have developed and validated an Affymetrix Inc. GeneChip array-based, whole-genome resequen- cing platform for Francisella tularensis, the causative agent of tularemia. A set of bioinformatic filters that targeted systematic base-calling errors caused by cross-hybridization between the whole- genome sample and the array probes and by deletions in the sample DNA relative to the chip reference sequence were developed. Our approach eliminated 91% of the false-positive single- nucleotide polymorphism calls identified in the SCHU S4 query sample, at the cost of 10.7% of the true positives, yielding a total base-calling accuracy of 99.992%.