Characterization of porin expression in Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae identifies isolates most susceptible to the combination of colistin and carbapenems.
Antimicrob Agents Chemother. 2013 Mar 4;
Authors: Hong JH, Clancy CJ, Cheng S, Shields RK, Chen L, Doi Y, Zhao Y, Perlin DS, Kreiswirth BN, Nguyen MH
We characterized carbapenem resistance mechanisms among 12 Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) clinical isolates, and evaluated their effects on the activity of 2- and 3-drug combinations of colistin, doripenem and ertapenem. All isolates were resistant to ertapenem and doripenem; 75% (9/12) were resistant to colistin. Isolates belonged to ST258 clonal group, and harbored blaKPC-2, blaSHV-12, and blaTEM-1. By time-kills, doripenem (8 μg/ml) and ertapenem (2 μg/ml) were inactive against 92% (11/12) and 100% (12/12) of isolates, respectively. Colistin (2.5 μg/ml) exerted bactericidal effects (range: 0.39-2.5 log10) against 78% (7/9) of colistin-resistant isolates. Colistin-ertapenem, colistin-doripenem and colistin-doripenem-ertapenem exhibited synergy against 42% (5/12), 50% (6/12) and 67% (8/12) of isolates, respectively. Expression of ompK35 and ompK36 porins correlated with each other (R2 = 0.80). Levels of porin expression did not correlate with colistin-doripenem or colistin-ertapenem synergy. However, synergy with colistin-doripenem-ertapenem was more likely against isolates with high porin expression than low expression (100% (8/8) vs 0% (0/4); p=0.002). Moreover, bactericidal activity (area under the bacterial killing curve) against isolates with high porin expression was greater for colistin-doripenem-ertapenem than colistin-doripenem or colistin-ertapenem (p≤0.049). In conclusion, colistin-carbapenem combinations may provide optimal activity against KPC-Kp, including colistin-resistant isolates. Screening for porin expression may identify isolates that are most likely to respond to a triple combination of colistin-doripenem-ertapenem. In the future, molecular characterization of KPC-Kp isolates may be a practical tool for identifying effective combination regimens.
PMID: 23459476 [PubMed - as supplied by publisher]