Background: Enterobacteriaceae that produce KPC often carry multiple β-lactamase genes, some conferring broad spectrum β-lactam resistance. Distinct β-lactamase resistome types may serve as markers of strain relatedness to identify potential outbreaks.
Methods: We studied 363 KPC-producing Enterobacteriaceae recovered from 81 distinct hospital point prevalence rectal culture surveys (Chicago region, 2010 - 2014). We characterized the β-lactamase resistome using a multiplex PCR targeting 49 gene families (including carbapenemase, extended spectrum β-lactamase [ESBL], plasmid-mediated AmpC [pAmpC], and narrow spectrum β-lactamase gene families; Acuitas® Resistome Test, OpGen). We identified distinct combinations of β-lactamase genes as ‘resistome types'. For minority resistome types, we assessed temporal-spatial clusters (2 or more KPC-producing Enterobacteriaceae of identical species and resistome type recovered from the same facility/survey date) suggesting intra-facility transmission. We tested cluster significance using binomial methods.
Results: Of the 363 KPC-producing Enterobacteriaceae, 86% were K. pneumoniae, 7% E. coli, and 6% Enterobacter spp. Including blaKPC, isolates carried a median of 5 β-lactamase genes (range, 1 to 8). SHV-type ESBL genes were detected in 167 isolates (46%); TEM-type ESBL, 17 (5%); CTX-M-type ESBL, 12 (3%); and pAmpC-type, 48 (13%).
Using 23 resistance genes detected, we identified 38 unique β-lactamase resistome types; the 2 most frequent types accounted for 71% of all isolates, and 10 types had ≥1% prevalence (Table).
Of the 69 isolates belonging to minority resistome types, 39 (57%) could be grouped into clusters. For example, for resistome type 6 (n=7), 5 K. pneumoniae isolates were recovered on a single day from one facility (P=0.002).
Conclusion: KPC-producing Enterobactericeae carry multiple β-lactamases, including ESBLs (SHV, TEM, CTX-M) and pAmpC. In our region, most isolates were associated with 2 dominant resistome types that would require whole genome sequencing to resolve transmission linkages. However, facility clustering of minority resistome types suggests that a resistome-based surveillance system can identify potential outbreaks to improve infection control.
M. Y. Lin,
R. D. Lyles, Chlorox: Employee , Salary
T. K. Wagner, OpGen: Employee , Salary
G. T. Walker, Opgen, Inc.: Employee , Salary
R. A. Weinstein, None
M. K. Hayden, None
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