Laboratoire des Microorganismes et Biomolécules Actives, Faculté des Sciences de Tunis, Université Tunis-El Manar, 2092, Tunis, Tunisia.
Eur J Clin Microbiol Infect Dis. 2012 Jul;31(7):1511-6. doi: 10.1007/s10096-011-1471-z. Epub 2011 Nov 8.
The objective of this investigation was to analyse the carriage rate of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in faecal samples of healthy humans in Tunisia and to characterise the recovered isolates. One hundred and fifty samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 μg/ml) for ESBL-positive E. coli recovery. The characterisation of ESBL genes and their genetic environments, detection of associated resistance genes, multilocus sequence typing (MLST) and phylogroup typing were performed by polymerase chain reaction (PCR) and sequencing. The presence and characterisation of integrons and virulence factors were studied by PCR and sequencing. ESBL-positive E. coli isolates were detected in 11 of 150 faecal samples (7.3%) and one isolate/sample was further characterised. These isolates contained the blaCTX-M-1 (ten isolates) and blaTEM-52c genes (one isolate). The ISEcp1 (truncated by IS10 in four strains) and orf477 sequences were found upstream and downstream, respectively, of all bla (CTX-M-1) genes. Seven different sequence types (STs) and three phylogroups were identified among CTX-M-1-producing isolates [ST/phylogroup (number of isolates)]: ST58/B1 (3), ST57/D (2), ST165/A (1), ST155/B1 (1), ST10/A (1), ST398/A (1) and ST48/B1 (1). The TEM-52-producing isolate was typed as ST219 and phylogroup B2. Six ESBL isolates contained class 1 integrons with the gene cassettes dfrA17-aadA5 (five isolates) and dfrA1-aadA1 (one). Healthy humans in the studied country could be a reservoir of CTX-M-1-producing E. coli.
本研究旨在分析突尼斯健康人群粪便样本中携带产超广谱β-内酰胺酶（ESBL）大肠杆菌的携带率，并对分离出的菌株进行特征描述。将 150 份样本接种于添加头孢噻肟（2μg/ml）的麦康凯琼脂平板，以分离 ESBL 阳性大肠杆菌。通过聚合酶链反应（PCR）和测序对 ESBL 基因及其遗传环境、相关耐药基因、多位点序列分型（MLST）和系统发育群分型进行了鉴定。通过 PCR 和测序研究了整合子和毒力因子的存在和特征。在 150 份粪便样本中检测到 11 份（7.3%）ESBL 阳性大肠杆菌分离株，其中一份样本进一步进行了特征描述。这些分离株包含 blaCTX-M-1（10 个分离株）和 blaTEM-52c 基因（1 个分离株）。所有 bla（CTX-M-1）基因上下游均发现 ISEcp1（4 株发生 IS10 截断）和 orf477 序列。CTX-M-1 产生产生菌中鉴定出 7 种不同的序列类型（ST）和 3 种系统发育群[CTX-M-1 产生产生菌的 ST/系统发育群（分离株数）]：ST58/B1（3）、ST57/D（2）、ST165/A（1）、ST155/B1（1）、ST10/A（1）、ST398/A（1）和 ST48/B1（1）。产 TEM-52 的分离株被鉴定为 ST219 和 B2 系统发育群。6 株 ESBL 分离株含有 1 类整合子，带有基因盒 dfrA17-aadA5（5 株）和 dfrA1-aadA1（1 株）。研究国家的健康人群可能是产 CTX-M-1 大肠杆菌的储库。
