Published Date: 2010-08-03 16:00:05
Subject: PRO/AH/EDR> E. coli ST131 - USA: emerging drug-resistant pathogen worldwide
Archive Number: 20100803.2607
E. COLI ST131 - USA: EMERGING DRUG-RESISTANT PATHOGEN WORLDWIDE
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Fri 30 Jul 2010
Source: Infectious Diseases Society of America [edited]
A new, drug-resistant strain of _E. coli_ is causing serious disease,
according to a new study, now available online, in the 1 Aug 2010
issue of Clinical Infectious Diseases.
The new strain, ST131, was a major cause of serious
antimicrobial-resistant _E. coli_ infections in the USA in 2007,
researchers found. This strain has been reported in multiple
countries and encountered all over the USA. 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 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."
[ProMED-mail has not served, in the past, as a major site for posting
information regarding Gram-negative resistant bacteria. The citation
for the study above is Johnson JR, Johnston B, Clabots C, Kuskowski
MA, Castanheira M: _Escherichia coli_ sequence type ST131 as the
major cause of serious multidrug-resistant _E. coli_ infections in
the United States. Clin Infect Dis 2010; 51(3): 286-94; abstract
available at <http://www.ncbi.nlm.nih.gov/pubmed/20572763>.
This clone is increasingly reported worldwide as a significant
pathogen causing community-associated infections such as urinary
tract infections and bacteremias as an extended-spectrum
beta-lactamase (ESBL) producing bacterium. This isolate ST (sequence
type) 131 is an O25:H4 (O is the somatic antigen and H is the
flagellar antigen) produces CTX-M-15 and a variety of other
resistance products and is resistant to fluoroquinolone and most
other antimicrobial groups . The isolates, to date, have retained
susceptibility to the carbapenem group of beta-lactams such as
ertapenem, imipenem, and kerosene.
The following discussion is extracted from the reference below:
CTX-M beta-lactamases (which stands for active against CefoTaXime)
were first isolated in Munich. Since 2000, CTX-M producing bacteria
have emerged worldwide as significant causes of community-onset
urinary tract infections and now are the most common type of ESBL
found in most of the world. CTX-M beta-lactamases are encoded by
genes that have been captured by mobile elements from the chromosomes
of environmental bacteria.
Risk factors for acquisition include repeated urinary tracts
infections, underlying kidney disease, previous antimicrobial usage,
previous hospital stays, nursing home residents, diabetes, liver
disease, and international travel.
Peirano G, Pitout JDD: Molecular epidemiology of _Escherichia coli_
producing CTX-M beta-lactamases: the worldwide emergence of clone
ST131 O25:H4. Int J Antimicrob Agents 2010; 35(4): 316-21. - Mod.LL]