1713. Biofilm Formation of Enterococcus faecalis Varies by Site of Isolation
Session: Poster Abstract Session: Studies of the Interface of Host-Microbial Interaction
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
Background: Enterococcus faecalis represents a minor component of the human gut microbiome, yet it is a major cause of extra-intestinal infections. Existing literature suggests that biofilm formation contributes to the pathogenesis of enterococcal infections. We evaluated human E. faecalis isolates to compare in vitrobiofilm formation of isolates from sites of colonization and infection. 

Methods: From 1997-1999, 402 total E. faecalis isolates were collected through the Minneapolis Veterans Affairs Medical Center, including 265 extra-intestinal isolates from the clinical microbiology laboratory, 64 fecal isolates from inpatient volunteers, and 73 fecal isolates from community volunteers. Of these, 174 isolates were evaluated for biofilm formation using a microtiter plate assay. Safranin dye retention of biofilm biomass was adjusted for planktonic cell growth to control for different planktonic growth rates between isolates, resulting in a “biofilm index.” Isolates with a biofilm index < 0.03 were identified as non-biofilm formers. 114 clinical, 28 inpatient fecal, and 32 community fecal isolates were evaluated. Clinical isolates (number per site) were from abscesses (9), bacteremia (21), wounds (20), and urine (62: 31 clean-catch, 31 indwelling catheters).

Results: Overall, 152 (87%) of the isolates formed biofilms. Fecal and clinical isolates did not differ significantly for the proportion forming biofilm. However, biofilm formation was less frequent among clean-catch urine isolates (68%) than among urinary catheter-associated isolates (94%: p = .02) or all other clinical isolates combined (94%: p = .0005).

Conclusion: In this large collection of human E. faecalis isolates, no difference in biofilm forming ability was found between fecal vs. extra-intestinal clinical isolates. However, clean-catch urine isolates were less likely to form biofilm than were catheter-associated urine isolates, or all other clinical isolates combined. This difference may reflect a propensity of enterococcal strains with good biofilm forming ability to colonize and/or infect foreign materials such as urinary catheters.

Anne-Marie Leuck, MD, Infectious Diseases, University of Minnesota, Minneapolis, MN and Gary M. Dunny, PhD, Microbiology, University of Minnesota, Minneapolis, MN


A. M. Leuck, None

G. M. Dunny, None

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