Urinalysis for Pathogens

Urine testing for pathogens is performed by urine culture (culture medium).

To distinguish pathogens caused by skin contamination of urine from infectious agents, determining the identity of the pathogen (in addition to determining the number of pathogens) is of great importance.

Typical skin pathogens are Staphylococcus epidermidis (90%) and other coagulase-negative staphylococci, as well as Staphylococcus aureus, Corynebacteria and Propionibacterium acnes.

The most common pathogens found in urine include:

  • Escherichia coli (up to 80% of cases).
  • Staphylococci (Staphylococcus saprophyticus).
  • Klebsiella (Klebsiella pneumoniae)
  • Proteus mirabilis
  • Enterococci (most common in mixed infection).
  • Enterobacter
  • Pseudomonas

Normal flora of the anterior urethra:

  • Z. B. Staphylococcus epidermidis
  • Acinetobacter

If bacteria are positively detected, a resistogram (antibiotic resistance determination) is performed.

The procedure

Material needed

  • Medium stream urine
  • Catheter urine
  • Urethral (urethral)/cervical (cervical) swab; deep urethral (urethral) swab is necessary for chlamydia and mycoplasma detection

Preparation of the patient

  • Process sample quickly

Interference factors

  • Not known

Standard values

Criteria for microbiological diagnosis of urinary tract infection or asymptomatic bacteriuria (presence of bacteria in urine):

  • Urinary tract infection:
    • Pathogen counts > 105 CFU/ml (obtained from “clean” midstream urine).
    • Pathogen counts of 103 to 104 CFU/ml may already be clinically relevant in the presence of clinical symptoms (symptomatic patients), provided that they are pure cultures (i.e., only one type of bacteria) of typical uropathogenic bacteria
    • Pathogen counts of 102 CFU/ml (at least 10 identical colonies); for urine culture from suprapubic urinary bladder puncture (bladder puncture).
  • Asymptomatic bacteriuria (ABU): pathogen counts > 105 CFU/ml in the absence of clinical signs of urinary tract infection in two urine samples.

Indications

  • Suspected urinary tract infection (UTI).
  • Complicated urinary tract infections
    • Generally in males and in children under 12 years of age.
    • In the case of functional or anatomical anomalies.
    • In relevant renal dysfunction and/or concomitant diseases that favor urinary tract infection.
  • Recurrent urinary tract infections (ie, two recurrences / six months or three recurrences / year).
  • Pyelonephritis
  • Z. n. urological interventions (eg cystoscopy / cystoscopy).
  • Pregnancy
  • Urinary tract infections in older age
  • Monitoring the success of therapy (except in uncomplicated cystitis).
  • Non-response to antibiotic therapy

Interpretation

Interpretation of increased values

  • Urinary tract infection

Interpretation of decreased values

  • Not relevant to the disease

Further notes

  • In the case of negative bacteriological findings and persistent symptoms or leukocyturia (increased excretion of white blood cells in the urine), infections with the following pathogens must be excluded:
    • Chlamydia
    • Mycoplasma
    • Mycobacteria (tuberculosis)