Bacterial multispecies invasion of human epithelial bladder cells

Abstract

Urinary tract infections (UTIs) are a worsening global health problem. Multispecies bacterial UTIs are common but are poorly recognized and understood. Here we developed host cell co-infection models combined with high resolution imaging to compare single- and multi-species infections with common uropathogens, uropathogenicEscherichia coli(UPEC),Klebsiella pneumoniaeandEnterococcus faecalis. We demonstrate cooperation and direct interactions specifically between UPEC andE. faecaliswithin host cells that corresponded to an increased frequency of host cell infection. 3D imaging showed UPEC rods orientated perpendicular to the major host cell axis within single-species intracellular bacterial communities (IBCs), whereas UPEC cells often envelopedE. faecalisin multispecies IBCs. Furthermore, during dispersal from host cells, only the Gram-negative bacteria underwent infection-related filamentation (IRF) in multispecies infections. These first insights into intra-species synergies during UTIs at a single cell level should provide research pathways towards better diagnosis and treatment.