To investigate the mechanisms of multiple resistance and the horizontal transfer of resistance genes in animal pathogens, we characterized the molecular structures of the resistance gene-related sequences in a multidrug-resistant Klebsiella pneumoniae strain R46 isolated from a rabbit. Molecular cloning was performed to clone the resistance genes, and minimum inhibitory concentrations (MICs) were measured to determine the resistance characteristics of the cloned genes and related strains. A conjugation experiment was conducted to assess the transferability of the resistance plasmids. Sequencing and comparative genomic methods were used to analyze the structures of the resistance gene-related sequences. The K. pneumoniae R46 genome consisted of a chromosome and three resistance plasmids named pR46-27, pR46-42, and pR46-270, respectively. The whole genome encoded 34 antibiotic resistance genes including a newly identified chromosome-encoded florfenicol resistance gene named mdfA2. pR46-270, besides encoding 26 antibiotic resistance genes, carried four clusters of heavy metal resistance genes and several virulence-related genes or gene clusters. The plasmid-encoded resistance genes were mostly associated with mobile genetic elements. The plasmid with the most similarity to the floR gene-harboring plasmid pR46-27 was pCTXM-2271, a plasmid from Escherichia coli. The results of this work demonstrated that the plasmids with multidrug resistance genes were present in animal-derived bacteria and more florfenicol resistance genes such as mdfA2 could be present in bacterial populations. The resistance genes encoded on the plasmids may spread between the bacteria of different species or genera and cause the resistance dissemination.

中文翻译：

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分离自兔的耐多药肺炎克雷伯菌肺炎克雷伯菌R46的分子表征。

为了研究动物病原体中多重耐药和耐药基因水平转移的机制，我们对分离自兔的多药耐药肺炎克雷伯菌菌株R46的耐药基因相关序列的分子结构进行了表征。进行分子克隆以克隆抗性基因，并测量最小抑制浓度（MIC）以确定克隆的基因和相关菌株的抗性特征。进行缀合实验以评估抗性质粒的转移性。测序和比较基因组方法用于分析抗性基因相关序列的结构。的肺炎克雷伯菌R46基因组由一条染色体和三个抗性质粒组成，分别称为pR46-27，pR46-42和pR46-270。整个基因组编码了34种抗生素抗性基因，其中包括一个新近鉴定的染色体编码的氟苯尼考抗性基因mdfA2。pR46-270除了编码26种抗生素抗性基因外，还携带4个重金属抗性基因簇和几个与毒力相关的基因或基因簇。质粒编码的抗性基因主要与移动遗传元件有关。与携带floR基因的质粒pR46-27最相似的质粒是pCTXM-2271，这是一种来自大肠杆菌的质粒。这项工作的结果表明，具有多药抗性基因的质粒存在于动物来源的细菌中，而更多的氟苯尼考抗性基因（例如mdfA2）则可能存在于细菌种群中。质粒上编码的抗性基因可能在不同物种或属的细菌之间传播，并导致抗性传播。