Both F17-like and type 1 pili promote intestinal colonization in mouse colonic crypts, and the high-affinity mannoside M4284 reduces intestinal colonization of uropathogenic Escherichia coli while simultaneously treating urinary tract infections without disrupting the composition of the gut microbiota. Uropathogenic E. coli (UPEC) are responsible for 80% of community-acquired and 65% of nosocomial urinary tract infections (UTI), which together affect 150 million people annually. UPEC establishes reservoirs in the gut, but the factors involved in this process have remained unknown. Here, Scott Hultgren and colleagues show that both F17-like and type 1 pili promote intestinal colonization and bind to distinct glycans on epithelial cells distributed along colonic crypts. Using the high-affinity mannose analogue, mannoside M4284, which inhibits the adhesive function of type 1 pili, the authors demonstrate that it effectively reduces intestinal colonization of UPEC, while simultaneously treating UTI without significantly disrupting the composition of the gut microbiota. The authors suggest that this selective depletion of intestinal UPEC by mannosides could be used to reduce the occurrence of UTIs. Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) affect 150 million people annually1,2. Despite effective antibiotic therapy, 30–50% of patients experience recurrent UTIs1. In addition, the growing prevalence of UPEC that are resistant to last-line antibiotic treatments, and more recently to carbapenems and colistin, make UTI a prime example of the antibiotic-resistance crisis and emphasize the need for new approaches to treat and prevent bacterial infections3,4,5. UPEC strains establish reservoirs in the gut from which they are shed in the faeces, and can colonize the periurethral area or vagina and subsequently ascend through the urethra to the urinary tract, where they cause UTIs6. UPEC isolates encode up to 16 distinct chaperone-usher pathway pili, and each pilus type may enable colonization of a habitat in the host or environment7. For example, the type 1 pilus adhesin FimH binds mannose on the bladder surface, and mediates colonization of the bladder. However, little is known about the mechanisms underlying UPEC persistence in the gut5. Here, using a mouse model, we show that F17-like and type 1 pili promote intestinal colonization and show distinct binding to epithelial cells distributed along colonic crypts. Phylogenomic and structural analyses reveal that F17-like pili are closely related to pilus types carried by intestinal pathogens, but are restricted to extra-intestinal pathogenic E. coli. Moreover, we show that targeting FimH with M4284, a high-affinity inhibitory mannoside, reduces intestinal colonization of genetically diverse UPEC isolates, while simultaneously treating UTI, without notably disrupting the structural configuration of the gut microbiota. By selectively depleting intestinal UPEC reservoirs, mannosides could markedly reduce the rate of UTIs and recurrent UTIs.

Fimbrial or nonfimbrial adhesins assembled by the bacterial chaperone-usher pathway have been demonstrated to play a key role in pathogenesis. Such an assembly mechanism has been exemplified in uropathogenicEscherichia colistrains with the Pap and the Fim systems. InPseudomonas aeruginosa, three gene clusters (cupA,cupB, andcupC) encodingchaperone-usherpathway components have been identified in the genome sequence of the PAO1 strain. The Cup systems differ from the Pap or Fim systems, since they obviously lack numbers of genes encoding fimbrial subunits. Nevertheless, the CupA system has been demonstrated to be involved in biofilm formation on solid surfaces, whereas the role of the CupB and CupC systems in biofilm formation could not be clearly elucidated. Moreover, these gene clusters were described as poorly expressed under standard laboratory conditions. ThecupBandcupCclusters are directly under the control of a two-component regulatory system designated RocA1/S1/R. In this study, we revealed that Roc1-dependent induction of thecupBandcupCgenes resulted in a high level of biofilm formation, with CupB and CupC acting with synergy in clustering bacteria for microcolony formation. Very importantly, this phenotype was associated with the assembly of cell surface fimbriae visualized by electron microscopy. Finally, we observed that the CupB and CupC systems are specialized in the assembly of their own fimbrial subunits and are not exchangeable.

We identified a new bacterial transporter, the Pseudomonas aeruginosa CupB3 protein, which is an outer membrane usher involved in pili assembly. In CupB3, the usher domain has fused during evolution with a POTRA (polypeptide‐transport‐associated)‐like domain found in TpsB transporters of two‐partner secretion systems. In TpsBs, the POTRA captures the TpsA passenger, which is then transported across the outer membrane through the TpsB β‐barrel. We named CupB3 a ‘P‐usher’ for POTRA‐like domain‐containing usher. We showed that CupB3 assembles CupB1 fimbrial subunits into pili and secretes CupB5, a TpsA‐like protein. The CupB3 usher domain has the function of a TpsB β‐barrel in CupB5 translocation. We revealed that the POTRA‐like domain is neither essential for CupB1 fimbriae assembly nor for cell surface exposition of CupB5, but is crucial to coordinate bona fide transport of CupB1 and CupB5 through the usher domain. The P‐usher defines a novel transport pathway involving a molecular machine made with old spare parts.