Journal Article

<i>Escherichia coli</i> Sequence Type ST131 as the Major Cause of Serious Multidrug-Resistant <i>E. coli</i> Infections in the United States

James R. Johnson, Brian Johnston, Connie Clabots, Michael A. Kuskowski and Mariana Castanheira

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 51, issue 3, pages 286-294
Published in print August 2010 | ISSN: 1058-4838
Published online August 2010 | e-ISSN: 1537-6591 | DOI: http://dx.doi.org/10.1086/653932
Escherichia coli Sequence Type ST131 as the Major Cause of Serious Multidrug-Resistant E. coli Infections in the United States

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Background. Escherichia coli sequence type ST131 (O25:H4), associated with the CTX-M-15 extended-spectrum β-lactamase, has emerged internationally as a multidrug-resistant pathogen but has received little attention in the United States.

Methods. From the SENTRY and Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) surveillance programs, 127 E. coli clinical isolates from hospitalized patients across the United States in 2007, stratified by extended-spectrum cephalosporin and fluoroquinolone phenotype and blaCTX-M-15 genotype, were assessed for phylogenetic group, ST131 status, susceptibility profile, virulence genotype, gyrA and parC sequence, and pulsed-field gel electrophoresis profile.

Results. The 54 identified ST131 isolates (all fluoroquinolone resistant) accounted for an estimated 17% of the source populations, including 67%–69% of isolates resistant to extended-spectrum cephalosporins or fluoroquinolones, 55% of those resistant to both fluoroquinolones and trimethoprim-sulfamethoxazole, and 52% of multidrug-resistant isolates. Their distinctive virulence profiles were more extensive compared with other antimicrobial-resistant isolates but similarly extensive compared with antimicrobial-susceptible isolates. Pulsed-field profiling suggested ongoing dissemination among locales, with concentration of blaCTX-M-15 within specific ST131 lineages. A historical ST131 isolate lacked the 2007 ST131 isolates' conserved fluoroquinolone resistance—associated single-nucleotide polymorphisms in gyrA and parC.

Conclusions. A single E. coli clonal group, ST131, probably caused the most significantly antimicrobial-resistant E. coli infections in the United States in 2007, thereby constituting an important new public health threat. Enhanced virulence and/or antimicrobial resistance compared with other E. coli, plus ongoing dissemination among locales, may underlie ST131's success. Urgent investigation of the sources and transmission pathways of ST131 is needed to inform mitigation efforts.

Journal Article.  4353 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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