Introduction. The bla CTX-M-3 gene has rarely been reported in Morganella morganii strains and its genetic environment has not yet been investigated. Aim. To identify the bla CTX-M-3 gene in M. morganii isolated from swine and characterize its genetic environment. Methodology. A M. morganii isolate (named MM1L5) from a deceased swine was identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and subjected to antimicrobial susceptibility testing. The bla genes were detected and then the genetic location and environment of bla CTX-M-3 were investigated by Southern blot and PCR mapping, respectively. The M. morganii bla CTX-M-3 gene was cloned and expressed in Escherichia coli . Results. Isolate MM1L5 harboured the bla CTX-M-3 and bla TEM-1 genes. The bla CTX-M-3 gene, located on the chromosome, was co-carried with an IS26 and bla TEM-1 gene by a novel 6361 bp IS26-flanked composite transposon, designated Tn6741. This transposon consisted of a novel bla CTX-M-3-containing module, IS26-ΔISEcp1-bla CTX-M-3-Δorf477-IS26 (named Tn6710), and a bla TEM-1-containing module, IS26-Δorf477-bla TEM-1-tnpR-IS26, differing from previous reports. Phylogenetic analysis showed a significant variation based on the sequence of Tn6741, as compared to those of other related transposons. Interestingly, although the cloned bla CTX-M-3 gene could confer resistance to ceftiofur, cefquinome, ceftriaxone and cefotaxime, one amino acid substitution (Ile-142-Thr) resulted in a significant reduction of resistance to these antimicrobials. Conclusion. This is the first time that bla CTX-M-3 has been identified on a chromosome from a M. morganii isolate. Furthermore, the bla CTX-M-3 gene was located with an IS26 element and bla TEM-1 gene on a novel IS26-flanked composite transposon, Tn6741, suggesting that Tn6741 might act as a reservoir for the bla CTX-M-3 and bla TEM-1 genes and may become an important vehicle for their dissemination among M. morganii .

中文翻译：

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从猪分离出的摩根氏摩根氏菌中新型bla CTX-M-3携带Tn6741转座子的分子表征。

介绍。该BLA CTX-M-3基因很少被报道，摩氏摩根菌及其遗传环境尚未调查。目标。为了鉴定分离自猪的摩根氏菌中的bla CTX-M-3基因，并表征其遗传环境。方法。甲M.摩根分离物（命名为MM1L5）已故猪使用时间飞行基质辅助激光解吸/电离质谱法（MALDI-TOF MS）来识别，并进行药敏试验。的BLA被检测到的基因，然后的遗传位置和环境 通过Southern印迹和PCR作图分别研究了bla CTX-M-3。所述M.氏摩根BLA CTX-M-3基因的克隆和表达在大肠杆菌中。结果。分离株MM1L5带有bla CTX-M-3和bla TEM-1基因。所述BLA CTX-M-3基因，位于染色体上，与被共进行IS 26和BLA TEM-1基因的一种新的6361 bp的IS 26 -flanked复合转座子，指定Tn的6741。该转座子由新型bla CTX-M-3组成 含模块，IS 26 -ΔIS ECP1-BLA CTX-M-3 -Δ orf477 -IS 26（名为Tn的6710），和一个BLA TEM-1含模块，IS 26 -Δ orf477-BLA TEM-1 -tnpR -IS 26，与以前的报告不同。系统发育分析表明，与其他相关转座子相比，基于Tn 6741的序列发生了显着变化。有趣的是，尽管克隆了bla CTX-M-3该基因可以赋予对头孢噻呋，头孢喹诺酮，头孢曲松和头孢噻肟的抗性，一个氨基酸取代（Ile-142-Thr）导致对这些抗微生物剂的抗性显着降低。结论。这是首次在摩根氏分离株的染色体上鉴定出bla CTX-M-3。此外，bla CTX-M-3基因与IS 26元件和bla TEM-1基因位于新型IS 26侧翼复合转座子Tn 6741上，表明Tn 6741可能充当bla CTX- M-3和 bla TEM-1基因，并可能成为其在摩根氏菌中传播的重要载体。