Uropathogenic
Escherichia coli
(UPEC) causes the majority of uncomplicated urinary tract infections (UTI), which affect nearly half of women worldwide. Many UPEC strains encode an annotated intimin-like adhesin (
ila
) locus in their genome related to a well-characterized virulence factor in diarrheagenic
E. coli
pathotypes. Its role in UPEC uropathogenesis, however, remains unknown. In prototype UPEC strain CFT073, there is an
ila
locus that encodes three predicted intimin-like genes
sinH
,
sinI
, and
ratA
. We used
in silico
approaches to determine the phylogeny and genomic distribution of this locus among uropathogens. We found that the currently annotated intimin-encoding proteins in CFT073 are more closely related to invasin proteins found in
Salmonella
. Deletion of the individual
sinH
,
sinI
, and
ratA
genes did not result in measurable effects on growth, biofilm formation, or motility
in vitro
. On average,
sinH
was more highly expressed in clinical strains during active human UTI than in human urine
ex vivo
. Unexpectedly, we found that strains lacking this
ila
locus had increased adherence to bladder cells
in vitro
, coupled with a decrease in bladder cell invasion and death. The
sinH
mutant displayed a significant fitness defect in the murine model of ascending UTI including reduced inflammation in the bladder. These data confirmed an inhibitory role in bladder cell adherence to facilitate invasion and inflammation; therefore, the
ila
locus should be termed invasin-like, rather than intimin-like. Collectively, our data suggest that loss of this locus mediates measurable interactions with bladder cells
in vitro
and contributes to fitness during UTI.