High-content screening identifies a critical role for P pili in early adhesion of uropathogenic Escherichia coli to bladder cells

Abstract

Abstract Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are notoriously difficult to treat due to the ability of UPEC to adhere to and invade urothelial bladder cells. UPEC strains encode a variety of adhesins whose roles in adhesion and invasion are not fully elucidated. Using a transposon insertion library derived from the UPEC clinical isolate CFT073, we developed a high-content screening assay to identify UPEC mutants with defects in early adhesion to human bladder epithelial cells. Of a total of 8,184 mutants screened, we recovered 82 (1.0%) and 54 (0.7%) mutants with decreased and increased adhesion, respectively. Surprisingly, nine low-adhesion hits mapped to the two P pili operons encoded by CFT073, which are usually thought to mediate adhesion to kidney cells rather than bladder cells. These results were reinforced by examination of six high-adhesion hits mapping to the operon coding for F1C pili, where disruption of F1C pili function resulted in increased P pili synthesis. Taken together, these findings reveal a critical role for P pili in UPEC adhesion to bladder epithelial cells, which may inform the development of anti-adhesion therapies to prevent UTI recurrence.