The dissemination of extended-spectrum β-lactamases encoding genes in Escherichia coli, especially in the uropathogenic O25b-ST131 E. coli clone, constitutes a real concern. We aimed to identify the molecular mechanisms of resistance to cephalosporins among E. coli clinical isolates and to estimate the prevalence of the uropathogenic O25b-ST131 clone in our study. Forty-two cephalosporin-resistant E. coli implicated in urinary tract infections were collected from the Regional Hospital of a southeastern Tunisian Island from April 2015 to August 2016. Molecular screening of β-lactamases encoding genes by PCR and sequencing showed that the majority of our isolates harbored bla_CTX-M gene (bla_CTX-M-15 [n = 36], bla_CTX-M-14 [n = 2]). Nevertheless, the bla_SHV, bla_TEM, and bla_OXA-1 genes were not detected. Various class C β-lactamases encoding genes were observed in association or not with bla_CTX-M genes and were as follows: bla_ampC (n = 14), bla_CMY-42 (n = 7), bla_CMY-2 (n = 1), and bla_DHA-4 (n = 1). The research of O25b-ST131 clone was carried out by duplex PCR (pabB and trpA genes) and revealed that most of our isolates (n = 30) belonged to this clone. We also noted that the majority of our isolates belonged to the B2 phylogenetic group (n = 32), five isolates to the B1 phylogenetic group, three isolates to the D phylogenetic group, and only two isolates belonged to the A phylogenetic group. Our study provides new epidemiological information about E. coli clinical isolates in this area. Indeed, this is the first report of CTX-M-14 producing O25b-ST131 E. coli in our country and the first report of DHA-4 and CMY-42 producing E. coli in Tunisia.

中文翻译：

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突尼斯岛尿路感染中产生CTX-M-15，DHA-4和CMY-42的O25b-ST131大肠杆菌克隆的特征。

在大肠杆菌中，特别是在尿致病性O25b-ST131大肠杆菌克隆中，广谱β-内酰胺酶编码基因的传播引起了人们的实际关注。我们旨在确定大肠杆菌临床分离株中对头孢菌素耐药的分子机制，并评估我们研究中尿路致病性O25b-ST131克隆的患病率。2015年4月至2016年8月，从突尼斯东南部地区医院收集了42例涉及尿路感染的头孢菌素耐药性大肠杆菌。通过PCR和测序对β-内酰胺酶编码基因的分子筛查表明，我们大多数人分离株带有bla _CTX-M基因（bla _CTX-M-15 [ n  = 36]，bla _CTX-M-14 [ n  = 2]）。但是，未检测到bla _SHV，bla _TEM和bla _OXA-1基因。观察到各种C类β-内酰胺酶编码基因是否与bla _CTX-M基因相关联，如下所示：bla _ampC（n  = 14），bla _CMY-42（n  = 7），bla _CMY-2（n  = 1）和bla _DHA-4（n = 1）。通过双链PCR（pab B和trp A基因）进行了O25b-ST131克隆的研究，结果表明我们分离出的大多数菌株（n  = 30）都属于该克隆。我们还注意到，我们的大多数菌株都属于B2系统发育组（n  = 32），五个菌株属于B1系统发育组，三个菌株属于D系统发育组，只有两个菌株属于A系统发育组。我们的研究为该地区的大肠杆菌临床分离株提供了新的流行病学信息。的确，这是在突尼斯首次产生CTX-M-14的O25b-ST131大肠杆菌的报道，也是首次产生DHA-4和CMY-42的大肠杆菌的报道。