The Prevalence of pks+ E. coli in Cystic Fibrosis

Cystic fibrosis (CF) patients experience higher risks of colorectal cancer, but pathogenesis is unclear. In the general population, polyketide synthase-positive (pks+) E. coli is impli-cated in intestinal carcinogenesis via production of colibactin, however relevance in CF is unknown. We investigated pks+ E. coli prevalence in CF at baseline and longitudinally, performing PCR on stool DNA extracts. Potential associations between pks+ E. coli and gastrointestinal inflammation or microbiome dynamics were analysed using faecal calprotectin and 16SrRNA gene taxonomic data. At baseline, no difference in pks+ E. coli carriage was identified between CF and healthy controls, 21/55(38%) vs 26/55(47%), p=0.32. Pks+ E. coli was not associated with significant differences in mean (SD) calpro-tectin concentration (124(154) vs 158(268) mg/kg; p=0.60), microbial richness (159(76.5) vs 147(70.4); p=0.50) or Shannon diversity index (2.78(0.77) vs 2.65(0.74); p=0.50) in CF. Lon-gitudinally, subjects demonstrated intra-individual variation in pks+ E. coli presence, however no significant difference in overall prevalence was observed. Thus, intesti-nal pks+ E. coli prevalence was not different between CF and healthy controls, nor associ-ated with differences in gut microbial profile or inflammation. Investigating effects of re-peat exposure on risk profile and analysis of older CF cohorts is necessary to identify if associations with colorectal cancer exist.