A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and commensals

Abstract

Urinary tract infection is among the most common infections worldwide, typically studied in animals and cell lines with limited uropathogenic strains. Here, we assessed diverse bacterial species in a human urothelial microtissue model exhibiting full stratification, differentiation, innate epithelial responses, and urine tolerance. Several uropathogens invaded intracellularly, but also commensal Escherichia coli , suggesting that invasion is a shared survival strategy, not solely a virulence hallmark. The E. coli adhesin FimH was required for intracellular bacterial community formation, but not for invasion. Other shared lifestyles included filamentation (Gram-negatives), chaining (Gram-positives), and hijacking of exfoliating cells, while biofilm-like aggregates were formed mainly with Pseudomonas and Proteus . Urothelial cells expelled invasive bacteria in Rab-/LC3-decorated structures, while highly cytotoxic/invasive uropathogens, but not commensals, disrupted host barrier function and strongly induced exfoliation and cytokine production. Overall, this work highlights diverse species-/strain-specific infection strategies and corresponding host responses in a human urothelial microenvironment, providing insights at the microtissue, cell, and molecular level.

Bacterial multispecies invasion of human epithelial bladder cells

“…Numerous studies have investigated UTI microbial interactions and biofilm formation in-vitro in liquid media (e.g., rich media, synthetic or human urine) and on catheters [34][35][36][37] , their effect on immune activation 15,17,38,39 , and in-vivo in animal models [40][41][42] (a list on further reading here: 8 ). However, hardly any studies have looked at bacterial coinvasion behaviour at single bladder cell level.…”

“…E. faecalis and UPEC are often associated with each other during outgrowth of cultures from UTI 13,14 and E. faecalis can suppress the immune activation, promoting UPEC virulence 15 . Recent studies have investigated co-colonization in UTI models 16,17 , but very limited information regarding bacterial invasion behaviours under liquid flow conditions simulating the bladder environment is available at high resolution at a single cell level.…”

Multispecies bacterial invasion of human host cells

“…E. faecalis and UPEC are often associated with each other during outgrowth of cultures from UTI (Fourcade et al 2015 , de Vos et al 2017 ) and E. faecalis can suppress the immune activation, promoting UPEC virulence (Tien et al 2017 ). Recent studies have investigated co-colonization in UTI models (Flores et al 2023 ,, Jafari and Rohn 2023 ), but very limited information regarding bacterial invasion behaviours under liquid flow conditions simulating the bladder environment is available at high resolution at a single cell level.…”