Soufi Leila, Sáenz Yolanda, Vinué Laura, Abbassi Mohamed Salah, Hammami Salah, Torres Carmen
1 Institute of Veterinary Research of Tunisia , Tunis, Tunisia .
Foodborne Pathog Dis. 2013 Dec;10(12):1075-7. doi: 10.1089/fpd.2013.1542. Epub 2013 Aug 29.
Integrons are important genetic elements implicated in acquisition and expression of antimicrobial resistance genes. Gene cassettes of class 1 integrons may be differently expressed depending on the Pc promoter variant. Thirty-four Escherichia coli isolates (carrying 38 class 1 integrons), recovered from poultry meat in previous studies in Tunisia and selected by their specific traits, were further characterized in this study. Integron promoter variants and the pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) of isolates were determined. Three types of promoter variants were identified among the 38 class 1 integrons (PcW, PcH1, and PcS); the weak promoters were the most predominant. A high clonal diversity of the E. coli strains was demonstrated by PFGE or by MLST. Fifteen PFGE profiles were detected among 19 integron-positive isolates of phylogroup B2, and 12 different sequence types were identified by MLST among the remaining 15 isolates (ST48, ST88, ST101, ST117, ST155, ST189, ST351, ST359, ST410, ST641, ST665, and one new ST). These data reflect that the presence of integrons in these isolates is not due to the clonal dispersion but to dissemination of genetic structures carrying integrons in different clones. To the best of our knowledge, this is the first report examining the gene cassette promoter variants in class 1 integrons of E. coli isolates from poultry meat origin. The predominance of promoters implicated in weak expression/high excision activity of gene cassette arrays is of interest because they could theoretically enhance the capacity of integrons to adapt to antibiotic pressure.
整合子是与抗菌耐药基因的获得和表达相关的重要遗传元件。1类整合子的基因盒可能因Pc启动子变体而有不同表达。从突尼斯先前研究中的禽肉中分离出的34株大肠杆菌（携带38个1类整合子），根据其特定特征进行选择，并在本研究中进一步表征。测定了整合子启动子变体以及分离株的脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）。在38个1类整合子中鉴定出三种类型的启动子变体（PcW、PcH1和PcS）；弱启动子最为常见。PFGE或MLST显示大肠杆菌菌株具有高度的克隆多样性。在19株B2系统发育群的整合子阳性分离株中检测到15种PFGE图谱，在其余15株分离株（ST48、ST88、ST101、ST117、ST155、ST189、ST351、ST359、ST410、ST641、ST665和一个新的ST）中通过MLST鉴定出12种不同的序列类型。这些数据表明，这些分离株中整合子的存在不是由于克隆扩散，而是由于携带整合子的遗传结构在不同克隆中的传播。据我们所知，这是第一份研究源自禽肉的大肠杆菌分离株1类整合子中基因盒启动子变体的报告。与基因盒阵列弱表达/高切除活性相关的启动子占优势是令人感兴趣的，因为从理论上讲，它们可以增强整合子适应抗生素压力的能力。
