Carbapenem resistant Enterobacteriaceae (CRE) are a class of bacteria that are resistant to multiple
antibiotics, including carbapenems, which are considered last-resort
drugs when other antibiotics have failed.
CRE, which tend to spread in
hospitals and long-term care facilities, cause an estimated 9,300
infections and 600 deaths in the United States each year, according to the U.S.
Centers for Disease Control and Prevention (CDC) - and incidence is on
‘Carbapenem resistant Enterobacteriaceae (CRE) is more widespread than previously thought, and it may well be transmitting from person to person asymptomatically.’
This family of highly drug-resistant and potentially deadly bacteria may
be spreading more widely - and more stealthily - than previously
thought, revealed a new study from Harvard T.H. Chan School of
Public Health and the Broad Institute of MIT and Harvard.
Researchers examined carbapenem resistant Enterobacteriaceae (CRE)
causing disease in four U.S. hospitals. They found a wide variety of CRE
species. They also found a wide variety of genetic traits enabling CRE
to resist antibiotics, and found that these traits are transferring
easily among various CRE species.
The findings suggest that CRE is more
widespread than previously thought, that it may well be transmitting
from person to person asymptomatically, and that genomic surveillance of
these dangerous bacteria should be increased.
The study will appear online in PNAS
(Proceedings of the National Academy of Sciences
"While the typical focus has been on treating sick patients with
CRE-related infections, our new findings suggest that CRE is spreading
beyond the obvious cases of disease. We need to look harder for this
unobserved transmission within our communities and healthcare facilities
if we want to stamp it out," said William Hanage, associate professor
of epidemiology at Harvard Chan School and senior author of the study.
Tom Frieden, director of the CDC, has called these 'nightmare
bacteria' because they are resistant to some of the last-ditch
treatments available to doctors battling resistant infections.
The researchers looked at about 250 samples of CRE from hospitalized
patients from three Boston-area hospitals and from one California
hospital. Their goal was to obtain a snapshot of the genetic diversity
of CRE, to define the frequency and characteristics of outbreaks, to
find evidence of strains being transmitted within and between hospitals,
and to learn how resistance is being spread among species. Previous
studies have typically examined just one outbreak at a time.
Researchers found what Hanage termed a "riot of diversity," both
among CRE species and among carbapenem resistance genes. They also found
that resistance genes are moving easily from species to species,
contributing to a continually evolving threat from CRE.
In addition, the researchers found resistance mechanisms that hadn't
been seen before - implying that there are more to be discovered. The
finding highlights the need for vigilance in searching for as yet
unknown forms of resistance as they evolve and emerge.
"The best way to stop CRE making people sick is to prevent
transmission in the first place," said Hanage. "If it is right that we
are missing a lot of transmission, then only focusing on cases of
disease is like playing Whack-a-Mole; we can be sure the bacteria will
pop up again somewhere else."