Thursday, August 12, 2010

Escherichia coli sequence type ST131 as the major cause of serious multidrug-resistant E. coli infections in the United States

Clin Infect Dis. 2010 Aug 1;51(3):286-94.

Escherichia coli sequence type ST131 as the major cause of serious multidrug-resistant E. coli infections in the United States.

Johnson JR, Johnston B, Clabots C, Kuskowski MA, Castanheira M.

Infectious Diseases,VA Medical Center, Minneapolis, MN 55417, USA.

Comment on:

Clin Infect Dis. 2010 Aug 1;51(3):280-5.


BACKGROUND: Escherichia coli sequence type ST131 (O25:H4), associated with the CTX-M-15 extended-spectrum beta-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 bla(CTX-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 bla(CTX-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.

PMID: 20572763 [PubMed - in process]


For Release: Friday, July 30, 2010

Contact Information Contact Name: John Heys Contact E-mail: Contact Phone: 703-299-0412

Emerging E. coli Strain Causes Many Antimicrobial-Resistant Infections in U.S.

A new, drug-resistant strain of E. coli is causing serious disease, according to a new study, now available online, in the August 1, 2010 issue of Clinical Infectious Diseases.

The new strain, ST131, was a major cause of serious antimicrobial-resistant E. coli infections in the United States in 2007, researchers found. This strain has been reported in multiple countries and encountered all over the United States. In the study, researchers analyzed resistant E. coli isolates collected during 2007 from hospitalized patients across the country. They identified 54 ST131 isolates, which accounted for 67 percent to 69 percent of E. coli isolates exhibiting fluoroquinolone or extended-spectrum cephalosporin resistance.

“If we could discover the sources of this strain, the transmission pathways that allow it to spread so effectively, and the factors that have led to its rapid emergence, we could find ways to intervene and possibly slow or halt this strain’s emergence,” said study author James Johnson, MD, of the VA Medical Center in Minneapolis.

In the past, highly virulent E. coli strains usually have been susceptible to antibiotics, while highly resistant strains have been fairly weak in terms of their ability to cause disease. The susceptible strains were easily treated even though they caused serious infections, while the resistant ones tended mostly to affect only weakened or vulnerable individuals. Now, the study’s findings suggest, the ST131 strain has appeared with a high level of virulence and antimicrobial resistance.

“If this strain gains one additional resistance gene,” Dr. Johnson added, “it will become almost untreatable and will be a true superbug, which is a very concerning scenario.”


Founded in 1979, Clinical Infectious Diseases publishes clinical articles twice monthly in a variety of areas of infectious disease, and is one of the most highly regarded journals in this specialty. It is published under the auspices of the Infectious Diseases Society of America (IDSA). Based in Arlington, Va., IDSA is a professional society representing more than 9,000 physicians and scientists who specialize in infectious diseases. For more information, visit

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