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BACKGROUND: Carbapenem-Resistant Enterobacteriaceae (CRE) has been a reportable condition in Tennessee since 2011. The Tennessee Department of Health recognizes CRE as a public health priority, and is utilizing the surveillance data in the NEDSS Base System (NBS) to describe patterns of resistance across the state.
METHODS: The case definition currently being recommended in the proposed 2015 position statement for the CSTE annual conference was applied to the 2014 Tennessee cases reported in NBS. Persons were counted as a case for a specimen of Enterobacter sp., Escherichia coli, or Klebsiella sp. resistant to a single carbapenem antibiotic (doripenem, ertapenem, imipenem, or meropenem) using the 2012 Clinical and Laboratory Standards Institute breakpoints. For this summary, each individual person was counted only once per organism for the year. Data were exported to Excel using an NBS template report, and then cleaned and analyzed in SAS 9.3. Cases were summarized according to the antimicrobial susceptibilities by organism and supplementary testing results. Additional summary statistics by source, region, and facility, and further analysis using ArcGIS 10.2 are pending.
RESULTS: Of the 133 cases identified with the above definition, 66 were due to Enterobacter sp., 23 were due to Escherichia coli, and 44 were due to Klebsiella sp. There was major geographic variation in the number of isolates and distribution of genera across the state. For 22 isolates, ertapenem was the only carbapenem tested. Sixty-four isolates were tested against ertapenem and another carbapenem, 42 isolates were not tested against ertapenem, and five isolates were missing MIC values. Among the 91 isolates tested against ertapenem, a total of 83 were resistant. For those 61 isolates resistant to ertapenem and tested against another carbapenem, 37 were susceptible, 2 were intermediate, and 22 were resistant to at least one other carbapenem tested. Of the 13 isolates with Modified Hodge Test results, 10 were positive. Fifteen isolates were tested using PCR for the bla(KPC) gene, which was detected in 10 isolates. Additionally, 15 of 37 isolates tested were positive for extended-spectrum beta lactamase.
CONCLUSIONS: The 2014 CRE antimicrobial susceptibility data were extracted from NBS and applied to the proposed CSTE definition. Availability of Modified Hodge test and bla(KPC) gene results was rare, emphasizing the importance of a phenotypic definition. Inclusion of ertapenem in susceptibility panels will be important to capture all cases meeting the new case definition.