Carbapenem-resistant Enterobacteriaceae, 2010

Enterobacteriaceae are a large family of Gram-negative bacilli (GNB) that cause community- and healthcare-associated infections. Commonly encountered species include Klebsiella pneumoniae, Escherichia coli, and Enterobacter cloacae. Carbapenem-resistant Enterobacteriaceae (CRE) are resistant to almost all available antibiotics including penicillins, cephalosporins and carbapenems. Genes encoding for carbapenemases, which confer resistance, may be either chromosomally- or plasmid-mediated, and can easily spread among bacteria of similar species. The most common plasmid-mediated carbapenemase found in the United States is the K. pneumoniae carbapenemase (KPC). In 2010, CDC reported the occurrence of two additional plasmid-mediated carbapenemases in the U.S.: 1) New Delhi Metallo-β-lactamase (NDM-1), and 2) Verona Integron-Encoded Metallo-β-lactamase (VIM). With few treatment options available, CRE represent an emerging public health threat in the United States and worldwide.

KPC-producing Enterobacteriaceae were first detected in North Carolina in 1999. MDH first detected a KPC-producing Enterobacteriaceae isolate in February 2009, and began statewide passive CRE surveillance in March 2009. MDH sent an alert to laboratory and healthcare personnel requesting submission of possible carbapenemase-producing isolates to the PHL for further characterization (e.g., PCR for the blaKPC gene).
During 2010, MDH tested 57 CRE isolates for presence of the blaKPC gene. Eighteen (32%) were blaKPC positive. Of these, 6 (33%) were cultured from the respiratory tract, 3 (17%) urine, 4 (22%) wound, 3 (17%) blood, and 2 (11%) drainage from an indwelling GI tract device. These isolates were K. pneumoniae (9), E. cloacae (7) and K. oxytoca (2).

The median age for cases with blaKPC positive isolates was 58 years (range, 1 year to 90 years); 10 (56%) were male. Of the 18 cases, 2 were known to be previously positive for blaKPC. Fifteen (83%) cases were hospitalized in an acute care or long-term acute care hospital at the time of culture, 1 (6.5%) was a long-term care facility (LTCF) resident, and 1 (6.5%) an outpatient. The LTCF resident and outpatient had histories of frequent exposure to multiple healthcare facilities. Three (17%) cases died though it was unclear whether the presence of a KPC-producing organism contributed to their deaths.

While the blaKPC gene was first detected in a K. pneumoniae isolate and is most frequently found in K. pneumoniae bacteria, we identified a cluster of 7 KPC-producing E. cloacae isolates in northwestern Minnesota. All 7 of these isolates were cultured from patients who had been hospitalized in one of two related healthcare facilities. Sites of culture included blood (1), sputum (2), urine (2) and GI tract device drainage (2). The PHL performed PFGE subtyping on available (6 of 7) isolates. PFGE results demonstrated that 4 of 6 isolates were genetically indistinguishable from one another and 2 were highly similar with 2 and 3 band differences, respectively; 5 control isolates had unrelated PFGE band patterns. Five cases were discharged to another healthcare facility, demonstrating the need for strict infection prevention measures and inter-facility communication of a patient’s CRE status to the receiving healthcare facility.

MDH is developing recommendations for the prevention and control of CRE in healthcare facilities across the continuum of care based on the CDC Guidance for Control of Infections with Carbapenem-Resistant or Carbapenemase-Producing Enterobacteriaceae in Acute Care Facilities and advice from local infection prevention experts. MDH has also recently established laboratory-based surveillance for CRE in Hennepin and Ramsey counties using the 2011 Clinical and Laboratory Standards Institute carbapenem breakpoints for Enterobacteriaceae. With sporadic reports of metallo-β-lactamases (e.g. NDM-1) in other parts of the United States and Canada, MDH will soon begin performing PCR for additional plasmid-mediated carbapenemase-producing genes (e.g., blaNDM-1).

Updated Monday, November 28, 2011 at 02:10PM