AmpC is a type of β-lactamase enzyme produced by bacteria; these enzymes are classified in Class C and Group 1, and these confer resistance to cephamycin. Enterobacterales producing AmpC are reported worldwide and have great clinical importance due to therapeutic restriction and epidemiological importance once the easy dissemination by plasmidic genes to other bacteria is a real threat. These genes are naturally found in some enterobacteria as Enterobacter cloacae, Morganella morganii, and Citrobacter freundii, but other species have demonstrated similar resistance phenotype of AmpC production. Genes carried in plasmids have been described in these species conferring resistance to cefoxitin and causing therapeutic failure in some bacterial infections. This work detected and described five clinical strains of Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae that presented plasmid ampC (pAmpC) isolated from the north of Portugal collected in 2009. AmpC production was confirmed by inhibition of the enzyme by cloxacillin and boronic acid in agar diffusion tests. Also, PCR (polymerase chain reaction) was performed for the detection of gene universal to AmpC, blaampC, and others to AmpC group: blaACC, blaCIT, blaCMY, blaDHA, and blaEBC. The conjugation in liquid medium for 24 h was realized to determine if gene is localized in chromosome or plasmid. The isolates and their conjugants showed phenotypic characteristics and blaCMY and blaCIT were detected by PCR corroborating the AmpC characteristics observed in these bacteria. Confirmation of transfer of plasmid containing genes encoding AmpC is of high epidemiological relevance to the hospital studied and demonstrated the importance of AmpC surveillance and studies in hospital and community environments in order to choose the appropriate therapy for bacterial infections.

中文翻译：

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在来自葡萄牙的大肠杆菌、奇异变形杆菌和肺炎克雷伯菌人临床分离株中检测到共轭质粒 AmpC

AmpC是一种由细菌产生的β-内酰胺酶；这些酶被归类为 C 类和 1 组，它们赋予对头霉素的抗性。产生 AmpC 的肠杆菌在世界范围内都有报道，并且一旦质粒基因容易传播到其他细菌成为真正的威胁，由于治疗限制和流行病学重要性，它们具有重要的临床意义。这些基因天然存在于某些肠杆菌中，如阴沟肠杆菌、摩根氏菌和弗氏柠檬酸杆菌，但其他物种已表现出类似的 AmpC 产生抗性表型。质粒中携带的基因在这些物种中被描述为赋予对头孢西丁的抗性并导致某些细菌感染的治疗失败。这项工作检测并描述了五种临床大肠杆菌菌株、奇异变形杆菌、2009 年收集的从葡萄牙北部分离的质粒 ampC (pAmpC) 和肺炎克雷伯菌。在琼脂扩散试验中，通过氯唑西林和硼酸对酶的抑制证实了 AmpC 的产生。此外，为了检测 AmpC、blaampC 和其他 AmpC 组的通用基因：blaACC、blaCIT、blaCMY、blaDHA 和 blaEBC，进行了 PCR（聚合酶链反应）。实现在液体培养基中结合24小时以确定基因是否定位于染色体或质粒中。分离物及其接合物显示出表型特征，通过 PCR 检测到 blaCMY 和 blaCIT，证实了在这些细菌中观察到的 AmpC 特征。