A comprehensive review of catheter-associated urinary tract infections: Pathogenesis, risk factors, clinical and laboratory features and contribution to hospital costs, morbidity and mortality

Abstract

Catheter-associated urinary tract infection (CAUTI) is the most common nosocomial infection in hospitals and nursing homes world-wide with more than one million episodes in the United States alone. We undertook a prospective observational study of 1,497 newly catheterized patients hospitalized at the University of Wisconsin Hopspitals and Clinics to determine the relative pathogenesis of the different microorganisms causing CAUTI, the risk factors for CAUTI in the modern era, the symptomatology of CAUTI, the association of CAUTI with pyuria and morbidity and mortality as well as the costs associated with CAUTI in the era of managed care. Overall, two thirds of infections were caused by organisms ascending along the surface of the catheter. This was more marked for staphylococci and enterococci as well as yeasts which are common commensals of the perineum. For Gram-negative organisms such as Pseudomonas, Enterobacter or Acinetobacter, the intraluminal route from the collection-bag was more important. The most important risk factors have been prolonged catheterization and being female. Other risk factors identified have included catheterization outside the sterile environment of the operating room, being on a urology service, other infections, diabetes, malnutrition and renal failure. We found that the proportion of catheterized patients without CAUTI with symptoms was similar to those with CAUTI. Symptoms cannot be relied on to distinguish ?asymptomatic bacteriuria? from urinary tract infections in patients with indwelling urinary catheters. We found pyuria to be most useful in predicting CAUTI in patients with UTI due to Gram-negative pathogens while CAUTI caused by large numbers of yeasts and enterococci or staphylococci were less significantly associated with pyuria. We also found that when other active infections were taken into account, CAUTI did not emerge as a significant risk factor for mortality in our large and vulnerable patient cohort. We showed that each CAUTI cost an approximate USD $500 and prolonged the average length of stay by a day. We have advanced our understanding of CAUTI by appreciating the differences in pathogenesis between the different microorganisms and also the reality that definitions used in non-catheterized patients cannot be automatically applied to patients with indwelling urinary catheters. Efforts to reduce CAUTI should be targeted at the different pathogenetic routes. Effective interventions to prevent CAUTI will doubtless help to reduce the reservoir of resistant pathogens in the intensive care units, wards and long-term care facilities. This will be a critical step in the battle against antibiotic resistance worldwide.