Research for infection protection

Urinary tract infection

With a share of 30 to 40 per cent, urinary tract infection (UTI) is one of the most common nosocomial infections. Around 80 per cent of all UTIs are associated with transurethral catheters. The risk of developing an infection increases proportionally with the duration of catheterisation: each day, 3 to 10 per cent of all patients with transurethral catheters acquire a bacteriuria. Half of the patients with permanent catheters develop a bacteriuria within 7 days. The most common pathogens are Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

More than 90 per cent of the catheter-related UTIs are asymptomatic. A precondition for the surveillance of UTI is the differentiation between symptomatic UTI and asymptomatic bacteriuria following the definitions of the Centers for Disease Control and Prevention (CDC) and the Robert Koch-Institute (see box).

Urinary tract infection
CDC/RKI Definitions

D1 Symptomatic urinary tract infection must meet at least one of the following criteria:

  • Patient shows at least one of the following signs or symptoms: fever (> 38 °C), urgency, frequency, dysuria, or suprapubic tenderness and a positive urine culture, that is, > 105 colonies/mL of urine with no more than 2 species of microorganisms.

  • Patient shows at least two of the following signs or symptoms: fever (> 38 °C), urgency, frequency, dysuria, or suprapubic tenderness and at least one of the following:

    • positive dipstick for leukocyte esterase and/or nitrate
    • pyuria (urine specimen with > 10 white blood cells/mL or > 3 white blood cells/high-power field of unspun urine (1,000-fold magnification))
    • microorganisms seen on Gram’s stain of unspun urine
    • two urine cultures with repeated isolation of the same uropathogen with > 102 colonies/mL in catheter urine
    • urine culture with < 105 colonies/mL of a single uropathogen in a patient being treated with an effective antimicrobial agent for a urinary tract infection
    • diagnosis by a physician
    • physician institutes appropriate antimicrobial therapy.

D2 Asymptomatic bacteriuria must meet at least one of the following criteria:

  • Patient has had an indwelling urinary catheter within 7 days before the culture, has no fever (> 38 °C) or other urinary tract symptoms, > 105 colonies/mL of urine with no more than 2 species of microorganisms.
  • Patient has not had an indwelling urinary catheter within 7 days before the first of two urine cultures, > 105 colonies/mL of urine, isolation of the same microorganism in at least two urine cultures, no more than 2 species, no signs of infection.