Objectives: The presence of a nonpathogenic organism on the surface of a urinary catheter might impede catheter colonization by pathogens and thus prevent urinary tract infection. Previously, we reported that preinoculating urinary catheters with a nonpathogenic strain of Escherichia coli (83972) significantly impeded catheter colonization in vitro by gram-positive bacteria (Enterococcus faecalis). To explore this phenomenon further, we investigated in vitro whether E. coli 83972 could likewise inhibit catheter colonization by gram-negative and fungal uropathogens (Providencia stuartii, uropathogenic E. coli, and Candida albicans).
Methods: For each of the three uropathogens tested, we examined three different incubation conditions: (a) E. coli plus uropathogen catheters were exposed to E. coli 83972 for 24 hours and then to a uropathogen for 30 minutes; (b) E. coli-alone catheters were incubated with E. coli for 24 hours and then in sterile broth for 30 minutes; and (c) uropathogen-alone catheters were incubated in sterile broth for 24 hours before the 30-minute incubation with the uropathogen. All catheters were subsequently incubated in sterile human urine for 24 hours. Catheters were then rinsed and sonicated to determine the numbers of adherent organisms per centimeter.
Results: Pre-exposure of the catheter to E. coli 83972 in all cases significantly reduced the number of uropathogens colonizing the catheter surfaces.
Conclusions: E. coli 83972 significantly impedes catheter colonization by all tested bacterial and fungal pathogens. The broad applicability of this particular approach to bacterial interference in vitro invites further exploration in vivo.