Emerging multidrug-resistant (MDR) Gram-negative bacilli (GNB), including Escherichia coli sequence type 131 (ST131) and its resistance-associated H30 subclone, constitute an ever-growing public health threat. Their reservoirs and transmission pathways are incompletely defined. To assess diarrheal stools as a potential reservoir for ST131-H30 and other MDR GNB, we cultured 100 clinical stool samples from a Veterans Affairs Medical Center clinical laboratory (October to December 2011) for fluoroquinolone- and extended-spectrum cephalosporin (ESC)-resistant E. coli and other GNB, plus total E. coli. We then characterized selected resistant and susceptible E. coli isolates by clonal group, phylogenetic group, virulence genotype, and pulsotype and screened all isolates for antimicrobial resistance. Overall, 79 of 100 stool samples yielded GNB (52 E. coli; 48 other GNB). Fifteen samples yielded fluoroquinolone-resistant E. coli (10 were ST131, of which 9 were H30), 6 yielded ESC-resistant E. coli (2 were ST131, both non-H30), and 31 yielded susceptible E. coli (1 was ST131, non-H30), for 13 total ST131-positive samples. Fourteen non-E. coli GNB were ESC resistant, and three were fluoroquinolone resistant. Regardless of species, almost half (46%) of the fluoroquinolone-resistant and/or ESC-resistant non-E. coli GNB were resistant to at least three drug classes. Fecal ST131 isolates closely resembled reference clinical ST131 isolates according to virulence genotypes and pulsed-field gel electrophoresis (PFGE) profiles. Thus, a substantial minority (30%) of veterans with diarrhea who undergo stool testing excrete antibiotic-resistant GNB, including E. coli ST131. Consequently, diarrhea may pose transmission risks for more than just diarrheal pathogens and may help disseminate clinically relevant ST131 strains and other MDR GNB within hospitals and the community.
Bibliographical noteFunding Information:
We thank the MVAMC clinical microbiology laboratory for assistance with sample collection. This material is based upon work supported by the Office of Research and Development, Medical Research Service, Department of Veterans Affairs, grants I01 CX000192 01 and I01 CX000920-01A1 (J.R.J.). The opinions expressed are strictly those of the authors and do not necessarily reflect those of the MVAMC or Department of Veterans Affairs. J.R.J. has received research grants or consultancies from Actavis, Crucell/Jannsen, ICET, Merck, Syntiron, and Tetraphase and has patent applications for tests to detect specific E. coli clones. The other authors report no financial conflicts of interest. This work, including the efforts of James R. Johnson, was funded by U.S. Department of Veterans Affairs (VA) (I01 CX000192 01 and I01 CX000920-01A1).