Characterization of dual-species biofilms of Klebsiella pneumoniae and Escherichia coli clinical isolates from patients with catheter-associated urinary tract infections

GALVAN, ESTELA M.; IELPI, LUIS

Washington DC

Conferencia; 1st ASM Conference on Polymicrobial Infections.; 2014

American Society for Microbiology

Urinary catheterization is frequent in hospitals and long term care facilities. Bacteriuria associated with long-term (>30 days) catheterization is often polymicrobial. Episodes of catheter-associated bacteriuria could be asymptomatic or may develop symptomatic lower and upper urinary tract infection and bacteremia. Establishment of biofilms constitutes a bacterial strategy for persistence on catheter surfaces. Our goal is to understand whether microbial community interactions in multi-species biofilms developed by bacteria associated with urinary tract infections could be either beneficial to the species involved or detrimental to one or more populations. First, we performed a retrospective study at a public hospital from Buenos Aires city, Argentina, to assess the local epidemiology of pathogens involved in polymicrobial bacteriuria in patients carrying a urinary catheter. We found K. pneumoniae and E. coli being the two most prevalent microorganisms co-isolated. Next, we evaluated the ability of K. pneumoniae and E. coli clinical strains to form single- and dual-species biofilms when grown on silicone in artificial urine medium. The analysis of single-species biofilm biomass by crystal violet staining showed that K. pneumoniae biofilms developed higher biomass than those of E. coli. Moreover, the number of cultivable cells being recovered from K. pneumoniae biofilms after 24 h was significantly higher than the number of cultivable cells recovered from E. coli biofilms, despite the fact that the initial binding of both bacterial species to the substrate was similar. Dual-species biofilms developed a total biomass similar to the one observed for K. pneumoniae in single-specie biofilms. Cultivability assays using selective media evidenced that K. pneumoniae constituted more than 90 % of the biofilm population after 24 h. Moreover, a decrease in E. coli cultivability in dual-species biofilms compared to single-specie biofilms was observed. Confocal laser scanning microscopy of dual-species biofilms, developed with bacteria harbouring plasmids that carry either gfp or m-Cherry protein genes, confirmed the E. coli was indeed being outnumbered by K. pneumoniae. Our findings suggest that the interaction between K. pneumoniae and E. coli in dual-species biofilms resulted in a detrimental effect over E. coli.