The Formation of Poly-Microbial Biofilms on Urinary Catheters

The number of catheter associated urinary tract infections (CAUTIs) increases every year. The increasing number of CAUTIs bears on fact that urinary catheters became second most often used foreign body inserted into human body. Over 40% of nosocomial infections are infections of urinary tract, especially infections of catheterised patients (Gorman & Jones, 1991). Despite good aseptic management, circa 50% of patients have bacteriuria in first 10–14 days of catheterisation (Morris & Stickler, 1998). The risk of urinary tract infections is significantly higher in long-term inserted catheters (28 days); the percentage of infected catheters in these patients gets near to 100% (Morris & Stickler 1998). The high number of CAUTIs is associated with biofilm mode of growth of microbes. The biofilm mode of growth is advantageous from several reasons. The artificial surface of the implants facilitates adhesion of bacteria, which can therefore form biofilm. The bacteria in biofilm are protected against drying, mechanical damage and other influences of the outer environment. In the human body the bacteria in biofilm are protected against the immunity system and antibiotic treatment (Stewart & Costerton, 2001). The higher resistance of biofilm bacteria to antimicrobials is a serious problem and the reason of common therapy failure. The extracellular polysaccharide matrix plays the key role in the resistance of biofilm to the antibiotics. It prevents the diffusion of the antibiotics to the bacterial cells, it is the reason of the higher concentration of antibiotic-reducing enzymes in the bacterial surroundings and it partakes on the change of microenvironment in the deeper layers of biofilm. These features play an important role in antibiotics resistance because the low pH reduces effect of some antibiotics (such as aminoglycosides) and the nutrition and oxygen deficiency leads to the growth stasis of bacteria (e.g. the beta-lactam antibiotics become ineffective). The biofilms grow easily also on the surface of other implants, such as venous, prosthetic of heart valves, orthopaedic devices etc. (Stewart et al., 2001). It’s estimated, that biofilms are associated with about 65 % of nosocomial infections (Licking 1999). With the inserted catheter, the bacteria can more easily attack urinary tract and urinary bladder (Tunney et al., 1999). There are also other complications that are linked with bacterial colonisation of urinary tract and catheters, e.g. blockage of catheters with crystallic deposits of bacterial origin, generation of gravels and pyelonephritis (Gorman & Tunney, 1997). The obstruction of the urine flow in catheters with crystallic deposits meets circa 50% of long-term catheterised patients; and there is no method of prevention of these deposits nowadays. Except of crystallic deposits that are result of metabolic dysfunction,