Multi-site Gram-negative Surveillance Initiative

Some types of bacteria are becoming resistant to all or nearly all antibiotics. This means that patients with infections from these bacteria might have few or no treatment options.  Three types of these resistant bacteria are carbapenem-resistant Enterobacteriaceae (“CRE”), carbapenem-resistant Acinetobacter and carbapenem-resistant Pseudomonas aeruginosa. Infections due to these organisms occur among patients in healthcare settings, and have high death rates. Data from this tracking project will help scientists understand illness caused by these bacteria, and help shape prevention strategies to contain and prevent the spread of resistant organisms.

Specifically, the EIP MuGSI surveillance project will:

  • Determine the extent of CRE, carbapenem-resistant Acinetobacter  and carbapenem-resistant Pseudomonas aeruginosa disease in the United States
  • Identify people most at risk for illness from these organisms
  • Measure trends of disease over time

In addition, the project provides infrastructure that allows future research to be done on these organisms and other Gram-negative bacteria.


The Multi-site Gram-negative Surveillance Initiative or MuGSI is a part of the CDC’s Emerging Infections Program (EIP) Healthcare-Associated Infections Community Interface (HAIC) activity.  Through MuGSI, CDC is conducting active population- and laboratory-based surveillance in a defined surveillance catchment for seven carbapenem-resistant organisms: Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Klebsiella pneumoniae, Klebsiella oxytoca, Acinetobacter baumannii and Pseudomonas aeruginosa.

Pseudomonas aeruginosa was added to the list of organisms under surveillance for MuGSI in July 2016. This organism was added because it causes an estimated 51,000 healthcare-associated infections, including pneumonia and surgical site, urinary tract, and bloodstream infections, in the United States each year. According to a CDC report, more than 6,000 (13%) of these infections are multidrug-resistant, with roughly 400 deaths per year attributed to these infections.

Surveillance Objectives

  1. To evaluate the population-based incidence of carbapenem resistance among the following organisms: Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Klebsiella pneumoniae, Klebsiella oxytoca, Acinetobacter baumannii and Pseudomonas aeruginosa, and to describe changes in incidence over time.
  2. To better characterize carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-resistant Pseudomonas aeruginosa (CR-PA) cases to understand epidemiologic characteristics and risk factors in cases in the areas under surveillance.
  3. To describe known resistance mechanisms among a subset of CRE and CR-PA isolates.

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MuGSI Surveillance Population
EIP Site 2011 2012 2013 2014 2015 2016
CO 2,583,519 2,636,542 2,694,889 2,694,889
GA 3,753,452 3,821,534 3,864,091 3,925,130 3,991,607 3,991,607
MD 3,917,263 1,926,832 1,934,018 1,934,018
MN 1,683,127 1,704,728 1,725,492 1,744,719 1,761,282 1,761,282
NM 674,221 675,551 676,685 676,685
NY 749,606 749,857 749,600 749,600
OR 1,668,648 1,690,785 1,709,394 1,734,682 1,766,135 1,766,135
TN 1,618,979 1,653,871 1,653,871
Total 7,105,227 7,217,047 13,223,586 15,012,292 15,228,087 15,228,087

U.S. Census web siteExternal was accessed on 6/27/2016.


Case Definition

For CRE and CR-PA surveillance, carbapenem resistance is defined as resistance to at least one of the carbapenem antibiotics (doripenem, imipenem, meropenem, or ertapenem (only CRE)). For CRAB surveillance, a case must have an isolate that is nonsusceptible (intermediate or resistant) to at least one carbapenem (excluding ertapenem).  The results of the primary antibiotic susceptibility testing methods (e.g. minimum inhibitory concentration (MIC), zone diameter interpretive criteria) used by participating local clinical laboratories are used to classify isolates as susceptible or nonsusceptible/resistant.

The CRE and CRAB case definition requires that the organism is isolated from a normally sterile body site or urine from residents of the surveillance area. For CR-PA surveillance, the case definition requires that CR-PA be isolated from a normally sterile body site, urine, lower respiratory tract specimen (i.e., sputum, bronchoalveolar lavage, tracheal aspirate), or wound.

Case-patient infections are described based on the information obtained through medical record review, and are categorized based on the patient’s location at the time of incident culture collection and/or where the patient was physically located at a defined time point prior to culture collection.

Recurrent and Persistent Cases

If a new culture meeting the case definition is collected more than 30 days after the patient’s initial case-defining positive culture, it will be reported as an incident case and a case report form will be completed. If a culture was collected less than 30 days after the initial positive culture, the case will be considered as having persistent infection and a case report form will not be completed. This occurrence will be considered a “non-incident” case for the MuGSI surveillance program.

Case Ascertainment

Cases are identified based on the local clinical laboratory’s antibiotic susceptibility testing data. Most local clinical laboratories conduct antibiotic testing using an Automated Testing Instrument (ATI). In many clinical laboratories within the surveillance catchment area, culture results meeting the MuGSI case definitions are identified directly from these ATI systems.

Data Collection

Data collection is performed by trained surveillance epidemiologists in each EIP site. For each incident case, medical record review is performed to gather patient demographic characteristics, location of culture collection, types of infections associated with the positive culture, underlying conditions, and healthcare exposures.

Laboratory Characterization

Isolates from incident cases are sent to CDC for molecular characterization. Additionally, CDC contributes some MuGSI isolates to the AR Isolate Bank.

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