Colonization and infection with fluoroquinolone-resistant Escherichia coliamong cancer patients: Clonal analysis

Escherichia coli with high-level fluoroquinolone resistance were isolated f rom feces and/or various body sites of 16 cancer patients who were on oral fluoroquinolone prophylaxis, Population analysis of fecal isolates in 11 pa tients showed that fluoroquinolone-resistant E, coli was the only aerobic g ram-negative bacillus present and exhibited a relatively homogenous fluoroq uinolone MIC distribution, Molecular typing by pulsed field gel electrophor esis of chromosomal DNA digests or by random amplified polymorphic DNA fing erprinting confirmed the clonal nature of gastrointestinal tract colonizati on with E. coli, Genotyping of ten colonies picked from the same fecal cult ure demonstrated identical strains in four of four patients examined. Ident ical genotypes from the same patient were isolated over prolonged periods o f time in 12 of 12 cases examined, with one patient (with the longest follo w-up of 14 months) who lost his initial genotype and became persistently co lonized with a new genotype. In the 11 patients who developed infection due to fluoroquinolone-resistant E, coli, molecular typing also indicated that fecal colonization was associated with, and presumably preceded infection due to an indistinguishable genotype of fluoroquinolone-resistant E, coli.