Centre for Infectious Diseases and Microbiology, The Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia.
Division of Infectious Disease and International Health, Department of Medicine, University of Virginiagrid.27755.32 Health System, Charlottesville, Virginia, USA.
Antimicrob Agents Chemother. 2022 Mar 15;66(3):e0232221. doi: 10.1128/aac.02322-21. Epub 2022 Jan 10.
Conjugative plasmids are the principal mediator in the emergence and spread of antibiotic resistance genes in Enterobacterales. Plasmid entry exclusion (EEX) systems can restrict their transfer into the recipient bacteria carrying closely related plasmids. In this study, we identified and characterized a novel plasmid entry exclusion system in a carbapenem resistance plasmid pKPC_UVA01, which is responsible for widespread dissemination of the carbapenemase gene among Enterobacterales in the United States. The identified gene in the recipient strain of different Enterobacterales species inhibited the conjugation transfer of pKPC_UVA01 plasmids at a range of 200- to 400-fold, and this inhibition was found to be a dose-dependent function of the EEX protein in recipient cells. The C terminus truncated version of or with an early termination codon at the C terminus region alleviated the inhibition of conjugative transfer. Unlike the strict specificity of plasmid exclusion by the known EEX protein, the newly identified EEX in the recipient strain could inhibit the transfer of IncP and IncN plasmids. The gene from the plasmid pKPC_UVA01 was not required for conjugative transfer but was essential in the donor bacteria for entry exclusion of this plasmid. This was a novel function of a single protein that is essential in both donor and recipient bacteria for the entry exclusion of a plasmid. This gene is found to be distributed in multidrug resistance plasmids similar to pKPC_UVA01 in different Enterobacterales species and may contribute to the stability of this plasmid type by controlling its transfer.
结合性质粒是肠杆菌目中抗生素耐药基因出现和传播的主要介质。质粒进入排除 (EEX) 系统可以限制它们转移到携带密切相关质粒的受体细菌中。在这项研究中，我们鉴定并表征了一种新型质粒进入排除系统，该系统存在于一种碳青霉烯类耐药质粒 pKPC_UVA01 中，该系统负责在美国肠杆菌目中广泛传播碳青霉烯酶基因。在不同肠杆菌目受体菌株中鉴定出的基因在 200-400 倍的范围内抑制了 pKPC_UVA01 质粒的接合转移，并且这种抑制被发现是受体细胞中 EEX 蛋白的剂量依赖性功能。C 端截断的 或 与 C 端区域的提前终止密码子减轻了对接合转移的抑制。与已知 EEX 蛋白对质粒排除的严格特异性不同，在受体菌株中鉴定出的新型 EEX 可以抑制 IncP 和 IncN 质粒的转移。质粒 pKPC_UVA01 中的 基因不是接合转移所必需的，但对于该质粒在供体细菌中的进入排除是必需的。这是一种单个蛋白的新功能，对于供体和受体细菌来说，该蛋白对于质粒的进入排除都是必需的。该 基因存在于与质粒 pKPC_UVA01 相似的不同肠杆菌目多药耐药质粒中，并且可能通过控制其转移来有助于这种质粒类型的稳定性。
