CDC Guidance For Control Of CRE
# 6937
Today’s MMWR has the details on an outbreak of NDM-Producing CRKP, or Carbapenem-Resistant Klebsiella pneumoniae, at an acute-care hospital in Denver during first 10 months of 2012. Klebsiella pneumoniae is a Gram negative, rod shaped bacterium commonly found in the flora of the human intestinal tract.
Most of the time, it resides harmlessly in the intestines.
But when K. pneumoniae moves beyond the intestinal tract – particularly in people with weakened immune systems – it can cause cause severe pneumonia, urinary tract infections (UTI), septicemia, and soft tissue infections.
Complicating matters, over the past decade doctors have seen the emergence of antibiotic resistant forms of K. pneumoniae – known as CRKP or KPC (K. pneumoniae carbapenemase).
Bacteria resistant to the Carbapenem class of antibiotics (a class that includes imipenem, meropenem, doripenem, and ertapenem) – are called carbapenemases – are of particular concern since Carbapenems are often the drug of last resort for treating difficult bacterial infections.
The reference to NDM-Producing is the detection of an emerging enzyme – called NDM or New Delhi metallo-beta-lactamase – that confers resistance to a number of different bacteria. The NDM enzyme was first detected in Sweden in 2008 from a patient with travel history to India.
Two and a half years ago The Lancet published a study (see NDM-1: A New Acronym To Memorize) by Walsh, Toleman, Livermore, et al. that sounded the alarm on the emergence and growing prevalence of the NDM-1 enzyme on the Indian sub-continent.
Of particular concern, this NDM enzyme is carried by a plasmid – a snippet of portable DNA - that can be easily transferred to other types of bacteria (see Study: Adaptation Of Plasmids To New Bacterial Species).
Since the discovery of NMD-1 5 years ago, scattered variants have begun to emerge; NDM-2, NDM-4, and NDM-5.
Up until now, the primary risk for contracting an NMD producing bacterial infection has been receiving medical care in those regions of the globe where these resistant strains have become endemic – notably South Asia.
But increasingly, these resistant organisms are making their way around the globe (presumably spread by asymptomatic carriers), and as the following report indicates, how it gets into a medical facility isn’t always known.
But once introduced, it can be very difficult to contain.
Notes from the Field: Hospital Outbreak of Carbapenem-Resistant Klebsiella pneumoniae Producing New Delhi Metallo-Beta-Lactamase — Denver, Colorado, 2012
Weekly
February 15, 2013 / 62(06);108-108On August 16, 2012, the Colorado Department of Public Health and Environment was notified of two patients at an acute-care hospital in Denver with carbapenem-resistant Enterobacteriaceae (CRE), specifically Klebsiella pneumoniae (CRKP), isolated from respiratory specimens during July–August. Both isolates produced New Delhi metallo-beta-lactamase (NDM). A review of microbiology records identified a third patient with NDM-producing CRKP isolated from a respiratory specimen, admitted in May. Active surveillance cultures in September identified an additional five patients colonized with NDM-producing CRKP. An investigation was launched by the hospital and the Colorado Department of Public Health and Environment to guide infection control measures and limit transmission.
A case was defined as NDM-producing CRE isolated from clinical or active surveillance cultures collected from a patient while hospitalized during January 1–October 30, 2012. Medical records were reviewed for clinical and epidemiologic characteristics. Relatedness of isolates was evaluated by pulsed-field gel electrophoresis (PFGE).
The eight patients were aged 23–75 years and had been hospitalized at one or more of 11 different units in the hospital for a median of 18 days (range: 12–83 days) before CRKP identification. Three were treated for CRKP infection, and five were found to be asymptomatically colonized; none died. Initial isolates were resistant to all antimicrobials except tigecycline, to which all were susceptible. Colistin minimum inhibitory concentrations for six isolates were low (≤2 µg/mL), suggesting this agent might be a treatment option. All isolates were highly related by PFGE. Epidemiologic tracing to determine temporal overlap of patients on units in the hospital indicated multiple transmission events had occurred, and three units were likely transmission sites. Acquisition of NDM-producing CRE by some patients was not explained by direct overlap and suggested that undetected, asymptomatically colonized patients were involved in some transmission routes. How NDM-producing CRE was introduced to the facility is unclear.
NDM, a carbapenemase enzyme first described in 2009 in a patient who had received medical care in India (1), has since been detected and reported worldwide (2). In the United States, before this outbreak, only 16 isolates in clusters with two or fewer cases had been identified since 2009; 14 isolates were from patients who had received medical care in endemic (South Asian) regions. The cases described here represent the largest U.S. outbreak of NDM-producing CRE to date, highlighting the risk for spread of these organisms among persons receiving medical care inside the United States. Evidence that undetected, asymptomatically colonized patients likely contributed to the size of the outbreak highlights the importance of timely active surveillance cultures when CRE is identified to direct infection control measures and limit further transmission (3).
Reported by
Larissa Pisney, MD, Michelle Barron MD, Div of Infectious Diseases, Univ of Colorado; Sarah Jackson Janelle, MPH, Wendy Bamberg, MD, Colorado Dept of Public Health and Environment. Duncan MacCannell, PhD, Antimicrobial Resistance and Characterization Laboratory; Alexander Kallen, MD, Carolyn Gould, MD, Brandi Limbago, PhD, Div of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases; Erin Epson, MD, Joyanna Wendt, MD, EIS officers, CDC. Corresponding contributor: Erin Epson, erin.epson@state.co.us, 303-692-2745.
While some of the warnings issued over the past couple of years regarding the growth and spread of antibiotic resistant organisms may have seemed a bit hyperbolic to the general public, I firmly believe that modern medicine will face no greater challenge over the next couple of decades.
Few, if any, new classes of antibiotics are in the pipeline, and with each passing day bacteria get better at evading our dwindling antibiotic arsenal.
The rise of antibiotic resistance - including these emerging NDM enzymes - has long been linked to the overuse and misuse of antibiotics. A practice that is still widespread in many parts of the world, but is particularly rampant on the Indian sub-continent.
Citing a lack of doctors and low family incomes, the Indian government (see India: Still Looking For A Policy On Antibiotics) has been slow to stop the sale of antibiotics to the public without a doctor’s prescription.
For more on the importance of proper antibiotic stewardship, you may wish to revisit these earlier blogs.
Chan: World Faces A `Post-Antibiotic Era’
And for a far more complete discussion of antimicrobial resistance issues, I can think of no better primer than Maryn McKenna’s book SUPERBUG: The Fatal Menace of MRSA.
Superbug (MRSA) Book
Meanwhile, Maryn’s SUPERBUG Blog, continues to provide the best day-to-day coverage of these issues.
