Exposure network analysis and molecular epidemiologic methods were used to analyze the emergence and regional spread of Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae over a 1-year period. Although 40 patients and 26 health care facilities were affected, 1 long-term acute care hospital played a critical role in the convergence of patients at high risk, amplification by cross-infection, and dissemination of these multidrug-resistant bacteria.
Background: Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae are an emerging antibiotic resistance threat with demonstrated epidemic potential.
Methods: We conducted an outbreak investigation of KPC-producing Enterobacteriaceae among patients of acute and long-term acute care hospitals (LTACHs) in 4 adjacent counties in Indiana and Illinois from 1 January 2008 through 31 December 2008 (cases). The study used traditional and molecular epidemiologic methods and an adaptation of social network analysis ("exposure network analysis").
Results: Clinical records for 40 (95%) of 42 patients were available. Patients were mostly older with multiple comorbid conditions. Eleven patients (27.5%) died during the index hospitalization or were discharged to hospice; 23 (57.5%) were discharged to a nursing home, and 4 (10.0%) were discharged to home. One LTACH (LTACH-A) was central to the regional outbreak: 24 (60%) of 40 cases were linked to LTACH-A, and at least 10 patients (25%) acquired KPC there. Of 16 cases not linked to LTACH-A, 12 (75%) were linked to 3 nursing homes. Only 4 patients (10%) definitely acquired KPC during an acute care hospital stay. Molecular typing revealed the 31 available KPC-positive K. pneumoniae isolates to be similar and to cluster with epidemic multilocus sequence type 258; 2 KPC-positive Escherichia coli isolates were unique.
Conclusions: We observed extensive transfer of KPC-positive patients throughout the exposure network of 14 acute care hospitals, 2 LTACHs, and 10 nursing homes. Although few cases were identified at most institutions, many facilities were affected. Successful control of KPC-producing Enterobacteriaceae will require a coordinated, regional effort among acute and long-term health care facilities and public health departments.