Urine Composition Following Trauma Facilitates Bacterial Growth

A new study suggests that changes in the composition of urine in critically ill patients, including trauma patients, place them at high risk of urinary tract infection (UTI).

Researchers at Université Paris Denis Diderot (France) and other institutions conducted a prospective observational study of 22 patients admitted to the surgical intensive care unit (ICU) of the University Hospital of Bicêtre (AP-HP, Paris, France), with severe trauma and without a history of UTIs or recent antibiotic treatment. The 24-hour urine samples were collected on the first and the fifth days and the growth of Escherichia coli in urine from patients and healthy volunteers was compared. Biochemical and hormonal modifications in urine that could potentially influence bacterial growth were explored.

The results showed that the growth of E. coli in urine from trauma patients was significantly higher on days 1 and 5 than in the urine of the healthy volunteers. The researchers found several significant modifications of urine composition that could explain the findings, including an increase in glycosuria, an increase in urine iron concentration, and an increase in the concentrations of several amino acids, urinary iron, and norepinephrine concentrations. This was accompanied by a significant decrease in urinary urea concentrations and osmotic pressure. The study was published on December 3, 2012, in BMC Infectious Diseases.

“The urine of trauma patients supports E. coli growth better than urine from healthy volunteers. This effect is present from the first 24 hours and remains at least until the fifth day after trauma,” concluded lead author Cecile Aubron, MD, PhD. “The effect is observed with antibiotic-resistant strains for patients who have received antibiotics, highlighting the impact of antibiotics on selection of resistant strains. This increase in the growth ability of E. coli strains in urine of trauma patients could be one of the elements facilitating UTIs in these patients.”

UTIs are the most common infections acquired by hospitalized adult patients, and account for up to 40% of hospital-acquired infections (HAIs); in approximately 15% of cases of nosocomial bacteremia, the urinary tract is implicated as the portal of entry. The occurrence of UTIs is increased in the presence of indwelling urinary catheters, a major risk factor of urosepsis because their presence allows bacteria to colonize the urinary tract. Other identified independent risk factors for bacteriuria in the ICU are gender (female), length of stay, and severity score at admission.

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Université Paris Denis Diderot -7
University Hospital of Bicêtre