A prospective study of pathogenesis of catheter-associated urinary tract infections

Objective: To determine the pathogenesis of catheter-associated urinary tra ct infection (CAUTI) and the relative importance of each of the possible me chanisms of entry of infecting microorganisms to the catheterized urinary t ract. Material and Methods: We conducted a prospective study of 1,497 newly cathe terized patients. Paired quantitative urine cultures were obtained daily, f rom the catheter specimen port and from the collection bag, using a techniq ue that could detect 1 colony-forming unit/mL, We assumed that with extralu minal infections, caused by microorganisms ascending from the perineum in t he mucous film contiguous to the external surface of the catheter, the orga nisms would be detected first in bladder urine or in far higher concentrati ons in urine from the specimen port than from the collection bag. With intr aluminal CAUTIs, caused by microorganisms gaining access to the catheter lu men because of failure of closed drainage or contamination of collection ba g urine, the organisms would be detected first or in far larger numbers in a collection bag specimen. Results: The probable mechanism of infection could be determined for 173 of 250 organisms (69.2%) identified in 235 new-onset CAUTIs, Among these 173 cases, 115 (66%) were extraluminally acquired, and 58 (34%) were derived fr om intraluminal contaminants, For these determinable cases, CAUTIs caused b y gram-positive cocci (enterococci and staphylococci) and yeasts were far m ore likely to be extraluminally acquired (extraluminal:intraluminal, 2.9) t han were gram-negative bacilli, which caused CAUTIs by both routes equally (extraluminal: intraluminal, 1.2; P = 0.007). Surprisingly, no significant differences were noted in pathogenetic mechanisms between men and women, Conclusion: We conclude that, in both men and women, CAUTIs occur by both e xtraluminal and intraluminal portals of entry but derive preponderantly fro m organisms that gain access extraluminally. Strategies for prevention of C AUTIs must focus on new technologies to prevent access of organisms by all possible routes.