747. Virulence profiles of Escherichia coli Sequence Type ST131 and non-ST131 E. coli in Clinical Stool Samples from Veterans
Session: Poster Abstract Session: Antimicrobials: Resistance Mechanisms
Friday, October 4, 2013
Room: The Moscone Center: Poster Hall C

E. coli ST131 is an emerging multi-drug resistant extraintestinal pathogen with undefined reservoirs and transmission pathways. We recently documented ST131 in clinical stool specimens from veterans. Here we molecularly assessed these organisms’ pathogenic potential, in comparison with non-ST131 E. coli from the same specimens.


100 stool samples from the Minneapolis VAMC clinical microbiology (Oct.-Dec. 2011) were cultured selectively for E. coli resistant (R) or susceptible (S) to fluoroquinolones and extended-spectrum cephalosporins. Isolates underwent PCR-based screening for ST131 status, phylogenic group (A, B1, B2, D), and 51 virulence factor genes (VFs) of extraintestinal pathogenic E. coli (ExPEC). ST131 and non-ST131 isolates were compared for VF content using Fisher’s exact and Mann-Whitney tests, dendrogram analysis, and principal coordinates analysis (PCoA).


Of 60 fecal E. coli isolates, 13 (9 R, 4 S) were ST131; 47 (39 S, 8 R) were non-ST131. Phylogenic group B2 predominated (38%), followed by groups A (25%), B1 (20%), and D (15%). Of 41 detected VFs, 4 were significantly ST131-associated, including iha ( 77% vs. 15% P=.001), usp (92 vs. 23% P=.001) , sat ( 62% vs. 11% P=.001) and malX (92% vs. 32% p=.001) as observed also among clinical isolates. ST131 isolates had higher VF scores (median 9, range 1-10) than non-ST131 R isolates (median 4, range 0-9:  P=.01).  Dendrogram analysis and PCoA demonstrated distinct, homogenous VF profiles for ST131 isolates. ST131 isolates more frequently qualified as ExPEC (6/13 [69%]) than did S (15/39 [38%]) or R (2/8 [25%]) non-ST131 isolates.


ST131 E. coli in clinical stool specimens from veterans appear more virulent than non-ST131 strains from the same samples and resemble ST131 clinical isolates. Thus, human feces may be a reservoir of virulent ST131 strains, and enhanced fitness in the intestinal niche may underlie ST131’s epidemiological success.

Sudershan J Singh, MD, Infectious Diseases, University of Minnesota, Minneapolis, MN, James R. Johnson, MD, University of Minnesota, Minneapolis, MN and Connie Clabots, Minneapolis VA Medical Center, Minneapolis, MN


S. J. Singh, None

J. R. Johnson, None

C. Clabots, None

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