Laboratory of Cellular and Molecular Biology, Biomedical Research Institute of Pontifical Catholic University of Rio Grande do Sul (PUCRS), Av. Ipiranga 6690, CEP 90610-000, Porto Alegre, RS, Brazil.
Int J Antimicrob Agents. 2013 Jul;42(1):76-9. doi: 10.1016/j.ijantimicag.2013.03.009. Epub 2013 May 10.
The emergence and spread of resistance mechanisms in Gram-negative bacilli has complicated the treatment of serious nosocomial infections. Current automated systems for detection of Klebsiella pneumoniae carbapenemase (KPC)-producing isolates are unreliable. One possible straightforward alternative method is evaluation of ertapenem resistance. However, the accuracy of this method is affected by other resistance mechanisms such as AmpC gene expression or extended-spectrum β-lactamase production associated with porin loss. This study included 128 samples of K. pneumoniae and Enterobacter spp. that were non-susceptible to ertapenem. The disk diffusion and Etest method were applied to determine susceptibility to imipenem, meropenem and ertapenem. Isolates exhibiting intermediate or complete resistance to ertapenem were evaluated for resistance mechanisms. bla(TEM), bla(SHV), bla(CTX-M), bla(CTX-M-2) and bla(KPC) genes were tested for by PCR, and the presence of outer membrane protein was investigated by dot-blot assay. bla(TEM) was detected in 52.9% and 10.3%, bla(SHV) in 29.4% and 0.94%, bla(CTX-M) in 41.4% and 1.9% and bla(CTX-M-2) in 23.5% and 1.9% of K. pneumoniae and Enterobacter cloacae isolates, respectively. The bla(KPC) gene was present in 12.6% of Enterobacter spp. isolates. OmpC and OmpF were present in 6.6% of E. cloacae isolates. These results indicate that several resistance mechanisms contribute to potential therapeutic failure of carbapenem therapy and point to the need for better detection methods and surveillance strategies.
革兰氏阴性杆菌耐药机制的出现和传播使严重医院获得性感染的治疗变得复杂。目前用于检测产碳青霉烯酶肺炎克雷伯菌（KPC）分离株的自动化系统不可靠。一种可能的直接替代方法是评估厄他培南耐药性。然而，这种方法的准确性受到其他耐药机制的影响，如与孔蛋白缺失相关的 AmpC 基因表达或广谱β-内酰胺酶的产生。本研究包括 128 株对厄他培南不敏感的肺炎克雷伯菌和肠杆菌属分离株。应用纸片扩散法和 Etest 法测定对亚胺培南、美罗培南和厄他培南的敏感性。对表现出对厄他培南中介或完全耐药的分离株进行耐药机制评估。通过 PCR 检测 bla(TEM)、bla(SHV)、bla(CTX-M)、bla(CTX-M-2) 和 bla(KPC)基因，并通过斑点印迹法检测外膜蛋白的存在。在肺炎克雷伯菌和阴沟肠杆菌分离株中，bla(TEM)分别检出 52.9%和 10.3%，bla(SHV)分别检出 29.4%和 0.94%，bla(CTX-M)分别检出 41.4%和 1.9%，bla(CTX-M-2)分别检出 23.5%和 1.9%。bla(KPC)基因存在于 12.6%的肠杆菌属分离株中。OmpC 和 OmpF 存在于 6.6%的阴沟肠杆菌分离株中。这些结果表明，几种耐药机制导致碳青霉烯类治疗的潜在治疗失败，并指出需要更好的检测方法和监测策略。
