Carbapenem-resistant Enterobacteriaceae, 2012

Enterobacteriaceae are a large family of Gram-negative bacilli that are common causes community- and healthcareassociated infections. Carbapenem resistant Enterobacteriaceae (CRE) are resistant to most available antibiotics. Some CRE bacteria harbor resistance genes that produce enzymes known as carbapenemases. Certain carbapenemases, such as the Klebsiella pneumoniae carbapenemase (KPC), are particularly concerning because they can easily spread between bacteria of similar species.

KPC continues to be the most common carbapenemase found in the United States. Since 2009, several types of metallo-β-lactamase (MBL)-producing Enterobacteriaceae have been reported in the United States, including New Delhi MBL (NDM) and Verona Integronencoded MBL (VIM). MBL-producing bacteria are more common outside the United States.

CRE infections most commonly occur among patients with significant health care exposures, co-morbid conditions, invasive devices, and those who have received extended courses of antibiotics. Invasive infections with CRE are associated with higher morbidity and mortality than carbapenem susceptible organisms.

MDH first detected a KPC-producing CRE isolate in February 2009, and began statewide voluntary reporting of CRE. As part of this surveillance, laboratories submit isolates from CRE patients to the PHL for further characterization.

In 2012, we adopted a standardized CRE case definition developed by the CDC EIP Gram-negative Surveillance Initiative, and made CRE reportable in the two most populous counties, Hennepin and Ramsey Counties. This definition includes isolates that are nonsusceptible to a carbapenem (excluding ertapenem) and resistant to all tested third generation cephalosporins using current CLSI breakpoints.

During 2012, 77 isolates from 76 patients were reported and tested by PCR for the blaKPC gene; 29 (38%) isolates from 28 patients were blaKPC positive; 2 isolates of different species were detected in 1 patient. Of the 29 incident blaKPC positive isolates, the median age of patients was 58 years (range, 7 months to 81 years); 19 (66%) were male and 12 (41%) were residents of the active surveillance area. Urine (14) was the most common source followed by sputum (4), wound (5), blood (2), peritoneal fluid (1), bone (1) and other respiratory sites (1). The most common species were K. pneumoniae (15) and E. cloacae (12). Eighteen (62%) were hospitalized (7 hospitalized >3 days prior to culture); median length of stay (LOS) was 14.5 days (range, 1 to 83). Ten (56%) required ICU care; in-hospital mortality was 22%. Other cases were from outpatient settings (5), long-term acute care hospitals (3), or long-term care facilities (2).

The PHL tests all CRE isolates by PCR for the blaNDM gene; 3 isolates from two non-Minnesota residents were blaNDM positive (K. pneumoniae [2] and E. coli [1]) during 2012. Both patients had significant health care exposure outside the United States. No blaNDM positive isolates were detected in Minnesota residents. To date, 2 blaNDM positive isolates (E. coli [1] and K. pneumoniae [1] from a single patient) have been detected in Minnesota residents.

CRE bacteria can spread in health care facilities (e.g., on the hands of health care workers) and have been associated with outbreaks in health care facilities in other states and other countries. The spread of CRE can be halted with early detection and implementation of appropriate infection prevention measures, and proper communication of CRE status when a colonized or infected patient is transferred.

In summary, over one third of CRE isolates reported were blaKPC positive; one patient had 2 blaKPC positive isolates of different species. Active surveillance testing should be considered when a patient with previously unrecognized CRE or hospital-onset CRE infections is identified or when a patient has been hospitalized outside the United States within the last 6 months. No outbreaks or transmission of CRE were reported among facilities that conducted active surveillance testing during 2012.

• For up to date information see>> "Superbugs": Carbapenem-resistant Enterobacteriaceae (CRE)
  
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2012