Microbial Biofilm Communities on Urinary Catheters: an Investigative Study of Catheterized Long Term Care Residents

Background: Biofilms are important in catheter-associated urinary tract infection (CAUTI), and are associated with increased morbidity and mortality in the healthcare environment. Important research questions regarding the role of biofilms in CAUTI include how systemic antimicrobial agents, type of catheter, or patient characteristics may affect rate of biofilm formation, diversity of organisms, or biofilm eradication.

Objective: Urinary catheters and urine specimens were collected as part of routine clinical care from residents in a long term care facility in order to investigate: a) whether each resident acquires a distinct biofilm-associated community on their urinary catheter and b) whether there is an association between resident characteristics and properties of the biofilm on the resident's catheter.

Methods: Fifteen urinary catheters were collected from 4 residents as part of routine clinical care and unrelated to the protocol. Multiple, sequential catheters were collected from each resident in order to assess biofilm properties over time and through multiple catheter exchanges. Catheters were processed to mechanically recover and quantify biofilm on the luminal surface. Organisms from the biofilm were isolated and identified and certain isolates were typed using pulsed field gel electrophoresis (PFGE). Resident characteristics including antimicrobial treatment regimens were also recorded.

Results: All catheters contained extensive biofilm formation (3.65 - 9.0 mean log CFU/cm²) and all contained multiple species (avg. 3.9 per catheter), but there was no clear association between number of species or type of organism, and biofilm density. Residents developed distinct microbial communities, as evidenced by the presence of identical strains of the same species over time and in subsequent catheters. The use of silver-treated catheters (2 of 4 catheters in one resident) or use of systemic antimicrobial treatments (in all residents) did not prevent biofilms. Routine flushing of suprapubic catheters with normal saline in one resident also had no measurable effect on biofilm density or number of species. However, despite the extensive presence of biofilms, only one of four residents developed a symptomatic CAUTI.

Conclusions: Residents with long term urinary catheters developed extensive biofilms containing multiple species. Each resident tended to acquire a biofilm community that was distinctly different in species composition. Silver-treated catheters, bladder washes, and systemic antimicrobial treatments did not prevent biofilm formation.