Mutations of the ompK36 porin gene and promoter impact responses of sequence type 258, KPC-2-producing Klebsiella pneumoniae strains to doripenem and doripenem-colistin.
Doripenem-colistin exerts synergy against some, but not all, Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains in vitro. We determined if doripenem MICs and/or ompK36 porin gene mutations impacted the responses of 23 sequence type 258 (ST258), KPC-2-producing strains to the combination of doripenem (8 μg/ml) and colistin (2 μg/ml) during time-kill assays. The median doripenem and colistin MICs were 32 and 4 μg/ml. Doripenem MICs did not correlate with KPC-2 expression levels. Five and 18 strains had wild-type and mutant ompK36, respectively. The most common mutations were IS5 promoter insertions (n = 7) and insertions encoding glycine and aspartic acid at amino acid (aa) positions 134 and 135 (ins aa134-135 GD; n = 8), which were associated with higher doripenem MICs than other mutations or wild-type ompK36 (all P values ≤ 0.04). Bactericidal activity (24 h) was achieved by doripenem-colistin against 12%, 43%, and 75% of ins aa134-135 GD, IS5, and wild-type/other mutants, respectively (P = 0.04). Doripenem-colistin was more active in time-kill studies than colistin at 12 and 24 h if the doripenem MIC was ≤8 μg/ml (P = 0.0007 and 0.09, respectively), but not if the MIC was >8 μg/ml (P = 0.10 and 0.16). Likewise, doripenem-colistin was more active at 12 and 24 h against the wild type/other mutants than ins aa134-135 GD or IS5 mutants (P = 0.007 and 0.0007). By multivariate analysis, the absence of ins aa134-135 GD or IS5 mutations was the only independent predictor of doripenem-colistin responses at 24 h (P = 0.002). In conclusion, ompK36 genotypes identified ST258 KPC-K. pneumoniae strains that were most likely to respond to doripenem-colistin.
University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
Cornelius J
CJ
Clancy
Liang
L
Chen
Jae H
JH
Hong
Shaoji
S
Cheng
Binghua
B
Hao
Ryan K
RK
Shields
Annie N
AN
Farrell
Yohei
Y
Doi
Yanan
Y
Zhao
David S
DS
Perlin
Barry N
BN
Kreiswirth
M Hong
MH
Nguyen
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015780:Carbapenems / Q000494:pharmacology*; D003091:Colistin / Q000494:pharmacology*; D000077726:Doripenem; D004338:Drug Combinations; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects / Q000235:genetics*; D004357:Drug Synergism; D015870:Gene Expression; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D015999:Multivariate Analysis; D009154:Mutation; D018272:Porins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D004338:Drug Combinations; C092233:OmpK36 protein, Klebsiella pneumoniae; D018272:Porins; D000077726:Doripenem; D001618:beta-Lactamases; C547585:beta-lactamase KPC-2, Klebsiella pneumoniae; D003091:Colistin