VANCOUVER—Enterococcus and Candida are the most frequent pathogens isolated in bloodstream infections (BSI) caused by nosocomial urinary tract infections (UTIs), according to University of Michigan researchers. 

In addition, Enterococcus infections are more common in patients with malignancy, neutropenia, and solid organ transplantation, and Candida infections are more common in patients with renal and liver disease.

“We found that these two infections stood out much more frequently than perhaps we necessarily expected,” said investigator Robert Chang, MD, Clinical Assistant Professor of Medicine. He presented study findings at the 48th Annual Meeting of the Infectious Diseases Society of America.

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Dr. Chang and his colleagues examined the epidemiologic features of patients with BSIs secondary to nosocomial bacteriuria and the temporal changes in microorganisms associated with these infections. The study included all patients with concurrent positive urine and blood cultures at a tertiary care hospital from January 2000 to December 2008.

The case definition was any hospitalized adult patient with a positive urine culture obtained more than 48 hour after admission and a blood culture obtained within 14 days of the urine culture that grew the same organism.

During the study period, 350 patients met the case definition, of whom 192 (54.9%) were men. The mean age of the patients was 58 years (range 21-92 years). Co-morbid conditions included renal disease (50.3% of patients), heart disease (48.6%), malignancy (39.7%), diabetes mellitus (24.6%), neutropenia (20.6%), and transplantation (19.1%).

The predominant organisms were Enterococcus species (27.7%), Candida species (20.0%), Escherichia coli (11.7%), coagulase-positive staphylococci (10.3%), and Pseudomonas species (8.9%). Among patients with a malignancy as their primary diagnosis, 34.5% had enterococcal infections. Among patients with neutropenia or had undergone solid organ transplantation, 44.4% and 40.3% had enterococcal infections. Among patients with renal disease and liver disease, 26.7% and 33.3%, respectively, were infected with Candida species.

“As far as I know this is the first study of its kind,” said Carol Chenowith, MD, Clinical Assistant Professor of Medicine. “In the past, we always assumed that most urinary tract infections resulting in a bacteriuria would be a gram negative organism. There has been a temporal change in organisms that are associated with bacteriuria from a urinary tract source, and if you are choosing empiric antibiotics you need to be aware that there have been some shifts in the types of organisms that we see.”

The potential influence of Enterococcus and Candida species should be considered in the context of patient comorbidities for appropriate presumptive antimicrobial therapy for nosocomial UTI-related BSIs, Dr. Chang said.