Use of Ancillary Carbapenemase Tests To Improve Specificity of Phenotypic Definitions for Carbapenemase-Producing Enterobacteriaceae

摘要

Carbapenem-resistant Enterobacteriaceae (CRE), particularly those that are resistant due to carbapenemase production, are a significant threat to public health. Infections caused by CRE are associated with a high attributable mortality (1), and U.S. surveillance data have demonstrated a steady increase in the burden of disease caused by CRE since 2000 (2). The U.S. CRE epidemic is driven, in part, by Klebsiella pneumoniae isolates of sequence type (ST) 258 that express the K. pneumoniae carbapenemase (KPC) (3). Transfer of patients colonized or infected with this organism between health care institutions is thought to have led to the dissemination of ST 258 K. pneumoniae across the country. One particularly well documented outbreak described by the Centers for Disease Control and Prevention Epicenter Program demonstrated that patient transfers between 26 health care facilities across four counties lead to the spread of KPC-producing CRE to 40 patients over a 1-year period (4). Subsequent studies in this region documented that nearly 1 in 3 residents of long-term acute care facilities were colonized with KPC-producing CRE (5). CRE harboring other carbapenem-hydrolyzing enzymes, such as NDM, VIM, IMP, or the OXA-48 type, common in other areas of the world (6), are also spreading in the United States (7–9). The introduction of isolates expressing these carbapenemases to a single institution by a patient traveling from an area of endemicity can lead to rapid spread, as occurred in our own institution when an OXA-232-producing K. pneumoniae strain was introduced to our facility by a colonized patient, leading to transmission of CRE to 14 patients via reprocessed duodenoscopes (10). A similar outbreak, caused by an NDM-producing K. pneumoniae strain in the Chicago area, was also recently documented as associated with the use of reprocessed duodenoscopes (11). In both outbreaks, rapid recognition of an unusual CRE type led to the epidemiological investigations that ultimately identified the source of the outbreak.