Mostly, bla_CTX-M is found on transferable plasmids as a component of the bla_CTX-M transposition unit containing an insertion sequence, ISEcp1, which exists on the upstream region of bla_CTX-Ms. Several recent studies conducted in clinical and community settings have reported the presence of chromosomally located bla_CTX-M in extended spectrum β-lactamase (ESBL)-producing bacterial isolates. In this study, we observed the frequency and molecular nature of the ISEcp1-mediated transposition of bla_CTX-M-14 from a plasmid to a chromosome by using an experimental strain of Escherichia coli. We determined 102 different chromosomal transposition sites of bla_CTX-M-14 in 126 E. coli isolates following five independent screening procedures. The characterization of the 102 different chromosomal transposition sites of bla_CTX-M-14 observed in this study revealed the presence of 5-bp direct repeat (DR) sequences and identical left terminal inverted sequences in 80 E. coli isolates. However, 5′-flanking sequences of the right terminal DR sequences in the 80 E. coli isolates were highly diverse, and consensus sequences of the right terminal inverted repeat sequences were not observed. In case of our E. coli experimental strain, the frequency of the ISEcp1-mediated transposition of bla_CTX-M-14 from a plasmid to a chromosome was determined to be 0.51% (SD = 0.37). Collectively, the molecular nature of ISEcp1 could plausibly be a factor contributing to the high detection rates of E. coli possessing chromosomally located bla_CTX-M-14 in both clinical and community settings.

通常，在可转移质粒上发现bla _CTX-M作为bla _CTX-M转座单元的一个组成部分，该单元包含一个插入序列IS Ecp1，该序列位于bla _CTX-M s的上游区域。在临床和社区环境中进行的几项最新研究报告了在产生_超广谱β-内酰胺酶（ESBL）的细菌分离物中存在位于染色体上的bla _CTX-M。在这项研究中，我们观察了IS Ecp1介导的bla _CTX-M-14从质粒到染色体的bla _CTX-M-14转座的频率和分子特性。大肠杆菌。在五个独立的筛选程序后，我们确定了126个大肠杆菌分离物中bla _CTX-M-14的102个不同的染色体转座位点。在这项研究中观察到的bla _CTX-M-14的102个不同染色体转座位点的特征揭示了在80个大肠杆菌分离物中存在5-bp直接重复（DR）序列和相同的左末端反向序列。然而，在80个大肠杆菌分离物中，右末端DR序列的5'侧翼序列高度多样化，并且未观察到右末端反向重复序列的共有序列。如果是我们的大肠杆菌在实验菌株中，经IS Ecp1介导的bla _CTX-M-14从质粒到染色体的转座频率确定为0.51％（S​​D = 0.37）。总的来说，IS Ecp1的分子性质可能是导致在临床和社区环境中具有染色体上位于bla _CTX-M-14的大肠杆菌高检测率的一个因素。