Are all nosocomial E. coli bacteriurias catheter-associated?

Background: E. coli is a common cause of bacteriuria and urinary tract infection in hospitals. It is thought that most nosocomial urinary tract infections are secondary to urinary catheters. Preventive strategies are therefore aimed exclusively at catheter management.   

Objective: To describe nosocomial E. coli bacteriurias and compare catheter-associated with non-catheter-associated episodes.  

Methods: We conducted a 7-month prospective cohort study of adult patients with nosocomial E. coli bacteriuria at a tertiary-care hospital. Urine cultures were performed at the discretion of the treating physician. Nosocomial bacteriuria was defined as bacteriuria occurring after the first 48 hours of admission. Catheter-associated bacteriuria was defined as presence of a urinary catheter within the 48 hours before positive urine culture. Asymptomatic bacteriuria was defined as absence of bladder symptoms; pyelonephritis as flank pain/tenderness ± fever.

Results: Of the 94 patients with nosocomial E. coli bacteriuria, 40 (43%) pts had catheter-associated bacteriuria. Among all bacteriuric patients, median age was 70 (range 23-95) years; 75 (80%) were female. 36 (38%) had asymptomatic bacteriuria, 15 (16%) had cystitis, 30 (32%) had pyelonephritis, and 13 (14%) were unable to report urinary symptoms (due to, e.g., altered mental status, intubation). In 36 (38%) patients a blood culture was obtained and 7/36 (19%) were bacteremic.

Patients with catheter-associated bacteriuria were more likely to have renal insufficiency [13/40 (33%) with catheter vs. 6/54 (11%) without catheter; p<0.001]. There were no differences in gender (p=0.6), age (p=0.5), diabetes (p=0.07), Charlson comorbidity score (p=0.8), and time to appropriate antibiotics (p=0.4). There was no difference in frequency of asymptomatic bacteriuria [16/40 (40%) with catheter vs. 20/54 (37%) without catheter; p=0.8]. Among the patients with blood cultures there was no difference in frequency of bacteremia [1/13 (8%) with catheter vs. 6/23 (26%) without catheter (p=0.4)]. In-hospital mortality was similar in catheter-associated vs. non-catheter-associated bacteriuria [4 (10%) vs. 6 (11%); p=0.6] as was length of hospital stay after bacteriuria (p=0.6). The presence of a catheter did not determine the receipt of susceptibility-matching antibiotics [39/40 (98%) with catheter vs. 47/54 (87%) without catheter (p=0.1)].

Conclusions: Less than fifty percent of nosocomial E. coli bacteriurias in this small cohort were catheter-associated. Patients with catheter-associated bacteriurias were more likely to have renal insufficiency but did not otherwise differ from those without urinary catheters. Most patients in this cohort received antibiotics, despite equal frequencies of asymptomatic bacteriuria.