Biofilm Formation by Uropathogenic Escherichia coli Is Favored under Oxygen Conditions That Mimic the Bladder Environment.

Allison Eberly,Spencer Colling,Maria Hadjifrangiskou,Charles Stratton,Connor Beebout,Jonathan Schmitz,Kyle Floyd,Madison Fitzgerald

doi:10.3390/ijms18102077

Abstract

One of the most common urologic problems afflicting millions of people worldwide is urinary tract infection (UTI). The severity of UTIs ranges from asymptomatic bacteriuria to acute cystitis, and in severe cases, pyelonephritis and urosepsis. The primary cause of UTIs is uropathogenic Escherichia coli (UPEC), for which current antibiotic therapies often fail. UPEC forms multicellular communities known as biofilms on urinary catheters, as well as on and within bladder epithelial cells. Biofilm formation protects UPEC from environmental conditions, antimicrobial therapy, and the host immune system. Previous studies have investigated UPEC biofilm formation in aerobic conditions (21% oxygen); however, urine oxygen tension is reduced (4–6%), and urine contains molecules that can be used by UPEC as alternative terminal electron acceptors (ATEAs) for respiration. This study was designed to determine whether these different terminal electron acceptors utilized by E. coli influence biofilm formation. A panel of 50 urine-associated E. coli isolates was tested for the ability to form biofilm under anaerobic conditions and in the presence of ATEAs. Biofilm production was reduced under all tested sub-atmospheric levels of oxygen, with the notable exception of 4% oxygen, the reported concentration of oxygen within the bladder.

Highlights

Urinary Tract Infection in the Context of Benign Urologic DiseaseUrinary tract infections (UTIs) account for 20 million hospital or clinic visits and billions of dollars in healthcare expenditures annually in the United States and Europe [1,2,3,4]
Men are less susceptible to urinary tract infection (UTI) than women, but their risk of infection increases with age
Our group has demonstrated that uropathogenic Escherichia coli (UPEC) mutants unable to use oxygen as the terminal electron acceptor are attenuated for virulence [39]. These findings suggest that UPEC isolates use aerobic respiration during UTIs

Summary

Urinary Tract Infection in the Context of Benign Urologic Disease

Urinary tract infections (UTIs) account for 20 million hospital or clinic visits and billions of dollars in healthcare expenditures annually in the United States and Europe [1,2,3,4]. 30% of women with a UTI will have recurrent infection [4,6]. Men are less susceptible to UTIs than women, but their risk of infection increases with age. UTIs are a common complication among hospitalized patients, among the elderly and patients with diabetes, bladder cancer, or indwelling catheters [9,10]. Current therapy for UTIs often fails, and this is exacerbated by the increased incidence of UTIs caused by bacteria resistant to common antimicrobials [11,12]

Uropathogenic Escherichia coli Biofilm Formation

Bacterial Strains

Biofilm Assays

Growth Curves and CFU Enumeration

Findings

Conclusions