Background: Long-term acute care hospitals (LTACHs) are important in regional dissemination of KPC, with LTACH patients acting as vectors of transmission during transfer between healthcare facilities.
Methods: We previously conducted a social network analysis (SNA) of a 2008 regional outbreak of KPC in metropolitan Chicago, and demonstrated a central role of one LTACH. Here, we performed whole-genome sequencing (WGS) on 35 isolates from 26 patients in 8 index healthcare facilities from that outbreak to assess whether WGS supported the SNA, and to determine if WGS could reduce residual uncertainty about origin and direction of transmissions within the network. We also sequenced 5 contemporary KPC isolates from an unrelated Chicago LTACH to test the hypothesis that the 2008 outbreak was the single origin of KPC in the region. Genomes were sequenced on Illumina MiSeq and single-nucleotide variants were identified by alignment to the finished KPNIH1 genome. Variants were filtered to remove low quality and horizontally acquired sequence, and these high-confidence variants were used to reconstruct the regional KPC phylogeny using RAxML.
Results: Phylogenetic analysis supports the hypothesis that regional spread of KPC in 2008 progressed by way of multiple independent exportation events from one LTACH (FIGURE, facility B). Closer inspection of the phylogenetic relationship among isolates from different facilities reveals instances where genomic similarities suggest a single importation of KPC into a facility, followed by transmission between patients (e.g., genomes 37 and 12, facility D). In other instances, genomic diversity suggests multiple independent importations (e.g., genomes 20 and 34, facility H). Placement of contemporary strains on the phylogeny indicates that while isolates derived from the original outbreak are still present in the region (C1 genome), there have since been additional importations of KPC (genomes C2, C18, C19, and C29).
Conclusion : WGS supports conclusions of previous SNA that one LTACH was the epicenter of regional KPC dissemination during an early, multi-facility outbreak. Comparison of original outbreak and contemporary KPC genomes suggests multiple subsequent introductions of KPC into the Chicago area.
E. S. Snitkin,
K. Lolans, None
S. Whitefield, None
R. A. Weinstein, None
K. Popovich, None
L. S. Munoz-Price, None
M. Y. Lin, None
M. K. Hayden, None
F. T. CDC Prevention Epicenters Program, None
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