High-Frequency Secondary Mutations after Suicide-Driven Allelic Exchange Mutagenesis in Extraintestinal Pathogenic <i>Escherichia coli</i>

Abstract

Frequent unintended secondary mutations occurred in extraintestinal pathogenic Escherichia coli strains CP9, CFT073, and RS218 during suicide plasmid-mediated, putatively specific deletions of hlyA, papG allele III, and iha. Pulsed-field gel electrophoresis and PCR analyses demonstrated genomic alterations and/or unintended loss of defined virulence genes (papG, the F7-2 papA allele, iutA, sat, hlyD, and cnf). Caution is warranted when attributing the observed phenotypic changes to the intended mutation.