Contribution of OmpK36 to carbapenem susceptibility in KPC-producing Klebsiella pneumoniae
Contribution of OmpK36 to carbapenem susceptibility in KPC-producing Klebsiella pneumoniae
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DOI：
10.1099/jmm.0.012575-0
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发表时间：
2009-10-01
影响因子：
3
通讯作者：
Quale, John
中科院分区：
文献类型：
--
作者：
Landman, David;Bratu, Simona;Quale, John
携带碳青霉烯酶 KPC 的肺炎克雷伯菌分离株的碳青霉烯类 MIC 仍处于敏感范围内，因此可能未被识别。为了了解碳青霉烯类 MIC 变异的机制，对 20 个临床分离株进行了检查，这些分离株均属于纽约市流行的 KPC 肺炎克雷伯菌的两个克隆组。通过实时 RT-PCR 检查编码 KPC、孔蛋白 OmpK35 和 OmpK36 以及外排泵 AcrAB 的基因的表达。通过 SDS-PAGE 检查所选 KPC 生产分离株的外膜特征，并通过基质辅助激光解吸/电离质谱法鉴定蛋白质。分别通过 PCR 和 DNA 测序确定 SHV 和 TEM β-内酰胺酶的鉴定以及 ompK35 和 ompK36 的基因组序列。对于一个克隆组，碳青霉烯类 MIC 随着 ompK36 表达的减少而增加，第二个克隆组也具有与 ompK36 表达相关的碳青霉烯类 MIC。然而，后一组中的所有分离株继续产生 OmpK36，表明孔蛋白构型可能影响碳青霉烯类的进入。对于 ompK36 表达最高的分离株，通过肉汤微量稀释技术测定时，碳青霉烯类 MIC 往往较低，并且在 Etest 抑制区周围可见分散的菌落。无论 ompK36 表达如何，所有产生 KPC 的分离株都对厄他培南高度耐药。总之，表达 ompK36 的 KPC 肺炎克雷伯菌分离株往往对碳青霉烯类具有较低的 MIC，因此可能更难以被临床实验室检测到。无论 ompK36 表达如何，所有 KPC 生产者始终对厄他培南具有耐药性。
Isolates of Klebsiella pneumoniae harbouring the carbapenemase KPC may have carbapenem MICs that remain in the susceptible range, and may therefore go unrecognized. To understand the mechanisms contributing to the variability in carbapenem MICs, 20 clinical isolates, all belonging to either of two clonal groups of KPC-possessing K pneumoniae endemic to New York City, were examined. Expression of genes encoding KPC, the porins OmpK35 and OmpK36, and the efflux pump AcrAB was examined by real-time RT-PCR. Outer-membrane profiles of selected KPC;producing isolates were examined by SDS-PAGE, and proteins were identified by matrix-assisted laser desorption/ionization mass spectrometry. The identification of SHV and TEM beta-lactamases and the genomic sequences of ompK35 and ompK36 were determined by PCR and DNA sequencing, respectively. For one clonal group, carbapenem MICs increased with decreasing expression of ompK36, A second clonal group also had carbapenem MICs that correlated with ompK36 expression. However, all of the isolates in this latter group continued to produce OmpK36, suggesting that porin configuration may affect entry of carbapenems. For isolates that had the greatest expression of ompK36, carbapenem MICs tended to be lower when determined by the broth microdilution technique, and scattered colonies were seen around the Etest zones of inhibition. All of the KPC-producing isolates were highly resistant to ertapenem, regardless of ompK36 expression. In conclusion, isolates of KPC-possessing K pneumoniae that express ompK36 tend to have lower MICs to carbapenems and therefore may be more difficult to detect by clinical laboratories. Regardless of ompK36 expression, all of the KPC producers were consistently resistant to ertapenem.