A SURFACE SWAB METHOD FOR CULTURING FOLEY CATHETERS ASSAYS THE PERICATHETER (URETHRAL) BUT NOT THE URINE (LUMINAL) MICROBIAL-POPULATION

Assessment of the urethral flora in patients with indwelling bladder c atheters is problematic ire the presence of urinary tract infection (U TI). A new surface swab method that samples the external catheter surf ace without interference from contaminated luminal contents is describ ed, In vitro, recovery of adherent bacteria from the external catheter surface by the surface swab method was proportional to the bacterial density as measured by a comparison scrape method. In a prospective lo ngitudinal assessment of three chronically catheterized subjects with polymicrobial catheter-associoted UTI, a conventional roll plate cathe ter culture method suggested substantial overlap between the urethral and urine microbial populations, possibly a result of contamination of catheter cultures by infected urine, In contrast, the surface swab me thod revealed little overlap between these floras, evidence suggesting a predominantly luminal (rather than meatal) route of UTI acquisition . The new surface swab method should prove useful in future studies of the pathogenesis and prevention of catheter-associated UTI.