[Dip-slides for culturing urine in general practice]

Abstract

Background: A consensus meeting at the Norwegian Institute of Public Health decided to change the limits for significant bacteriuria (used in microbiology laboratories) from 104 to 103 colony-forming units per ml. Such a low threshold value is difficult to read on dip-slides; NOKLUS (Norwegian quality improvement of laboratories in primary care) therefore wished to review the use of dip-slides in general practice.

Material and methods: The article is based on literature retrieved through a non-systematic search in PubMed and on the authors' experience and research in the field.

Results: Escherichia coli (E coli) is the most common agent in both lower and upper urinary tract infections, and in asymptomatic bacteriuria in pregnant women. In most infections, and particularly in upper urinary tract infections, bacterial concentrations are at least 104 colony-forming units per ml of urine in monocultures. Dip-slides should be the preferred transport medium when transport takes more than two days (because the number of colonies is not affected), otherwise urine samples with boric acid as a preservative are preferred.

Interpretation: Dip-slides with E coli-agar may provide important information on complicated (especially upper) urinary tract infections and when examining pregnant women for asymptomatic bacteriuria. Dip-slides should not be used in uncomplicated cystitis. Medical practices using dip-slides must achieve and maintain sufficient expertise, and participate in an external quality assurance system. Proper sampling and handling of urine is even more important than before because of the lower threshold for significant bacteriuria.