**2. Catheter associated urinary tract infection**

In addition to being the most common bacterial infection, UTIs are also the most common type of hospital acquired infections (HAI). HAIs can be defined as a localized or systemic condition resulting from an adverse reaction to the presence of an infectious agent or toxin, which occurs in a patient in a health care setting and was not present or incubating at the time of admission [64, 66]. UTIs account for 30% of all HAI [77]. Of these 30% infections, 80% of them are estimated to be catheter-associated [89]. According to the CDC, CAUTIs are defined as an UTI in a patient who had an indwelling urinary catheter in place at the time of or within 48 hours prior to infection onset. CAUTI can lead to complications such as cystitis, pyelonephritis, gramnegative bacteremia, prostatitis, epididymitis, endocarditis, vertebral osteomyelitis, septic arthritis, endophthalmitis and meningitis [20]. Additionally CAUTIs also result in prolonged hospital stay, increased cost and mortality [77]. An estimated 15-25% of hospitalized patients will have a urinary catheter at some point during their hospital stay [175]. Obstruction of indwelling catheters can lead to sepsis, even resulting in mortality [174]. Each year around 13,000 deaths are attributed to UTIs in the United States [77]. The cost associated with CAUTI episodes is about \$750-\$1000 per infection, and the estimated total cost in the United States ranges from \$340-\$450 million annually [132].

Millions of transurethral, suprapubic and nephrostomy catheters or urethral stents are used in patients every year. These devices overcome several host defenses and enable bacterial entry at a rate of 3 to 10% (cumulative rate) per day, which leads to bacteriuria in patients after a month [8]. In intubated patients, bacteria frequently ascend from the urethral meatus into the bladder between the mucosal and catheter surfaces. In certain cases, bacteria may ascend through the drainage system due to contamination of the drainage bag or disruption of the tubing junction. The presence of a device enables the persistence of the etiologic organism in the urinary tract. Several studies have demonstrated that bacteria exist as biofilms on these devices [53]. Formation of a biofilm and incrustation with calcium and magnesium struvites has a significant role in the pathogenesis and treatment of catheter-associated infections.
