Assessment of the urethral flora in patients with indwelling bladder catheters is problematic in the presence of urinary tract infection (UTI). A new surface swab method that samples the external catheter surface without interference from contaminated luminal contents is described. 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 longitudinal assessment of three chronically catheterized subjects with polymicrobial catheter-associated UTI, a conventional roll plate catheter 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 method 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.
Bibliographical noteFunding Information:
From the Department of Medicine, the Department of Physical Medicine and Rehabilitation, and the Department of Urological Surgery, University of Minnesota; and the Medical Service, Veterans Affairs Medical Center. Supported in part by Rochester Medical Corp., StewartviUe, Minn. (J.R.J. and J.J.B.); and by National Institutes of Health Grant DK-47504 (J.R.J. and J.J.B.). Submitted for publication Nov. 21, 1996; accepted Feb. 13, 1997. Reprint requests: James R. Johnson, MD, Infectious Diseases Service, lllF, VA Medical Center, 1 Veterans Drive, Minneapolis, MN 55417. 0022-2143/97 $5.00 5/1/81869