The objective of this study was to isolate and characterize ESBL-producing Escherichia coli (ESBL-EC) from raw bovine and caprine milk samples, as well as from bovine faeces in Tunisia. Therefore, 120 bovine faecal samples and 9 caprine raw milk samples were collected from 2 extensive dairy-cow-farms and 5 ovine farms, respectively. In addition, 94 raw bovine milk samples, from containers and holding tanks from 50 small public-markets in the North of Tunisia, were processed for the isolation of cefotaxime-resistant E. coli (CTXR). Antimicrobial susceptibility testing was carried out by disc-diffusion/broth-microdilution methods. The presence of genes encoding ESBL, as well as those encoding colistin (mcr-1 to 5 genes)- sulfonamide-, tetracycline-, gentamicin-, quinolone and chloramphenicol-resistance and class 1 integrons were tested by PCR (and sequencing in some cases). ESBL-EC isolates were further characterized by phylogrouping and MLST/PFGE typing. Eight samples (3.6%) contained ESBL-EC isolates (3/2 from raw bovine/goat milk and 3 from cattle faeces) and one isolate/sample was characterized. Four ESBL-EC isolates, all of bovine origin (3 faeces/1 milk), were resistant to colistin (MIC: 8-16 μg/ml), harboured the mcr-1 gene and carried IncP- and IncFIB-type plasmids. The 8 ESBL-EC strains had the following characteristics: a) bovine faeces: mcr-1/CTX-M-1/D-ST1642 (3 strains); b) raw milk: mcr-1/CTX-M-1/A-ST10 (1 strain); CTX-M-15/B1-ST394 (3 strains), and CTX-M-15/A-ST46 (1 strain). Most of bovine ESBL-EC isolates were multidrug-resistant (4/5). Our results showed that ESBL-EC were detected in bovine and caprine samples (CTX-M-1/CTX-M-15 producers), being some of them colistin-resistant (associated with mcr-1 gene), and they belonged to international clonal lineages.

中文翻译：

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mcr-1编码突尼斯产牛和山羊的产CTX-M-1 / CTX-M-15的大肠杆菌分离物中大肠菌素抗性。山羊CTX-M-15-ST394 / D大肠杆菌的首次报道。

本研究的目的是从突尼斯的原始牛乳和山羊乳样品以及牛粪中分离和鉴定生产ESBL的大肠杆菌（ESBL-EC）。因此，分别从2个大型奶牛场和5个养羊场中收集了120份牛粪便样品和9份山羊奶原料样品。此外，还对突尼斯北部50个小型公共市场的容器和储罐中的94份原始牛乳样品进行了处理，以分离出耐头孢噻肟的大肠杆菌（CTXR）。通过圆盘扩散/肉汤微稀释法进行了药敏试验。存在编码ESBL的基因，以及编码粘菌素（mcr-1至5个基因）的基因-磺酰胺类，四环素类，庆大霉素类，通过PCR（在某些情况下进行测序）测试了对喹诺酮和氯霉素的抵抗力以及1类整合素。通过系统分组和MLST / PFGE分型进一步鉴定ESBL-EC分离株。八个样品（3.6％）包含ESBL-EC分离株（来自生牛/山羊奶的3/2和来自牛粪的3个），并鉴定了一个分离株/样品。四个来源于牛的ESBL-EC分离株（3粪便/ 1牛奶）均对大肠菌素具有抗性（MIC：8-16μg/ ml），具有mcr-1基因并带有IncP-和IncFIB型质粒。8个ESBL-EC菌株具有以下特征：a）牛粪：mcr-1 / CTX-M-1 / D-ST1642（3个菌株）；b）生乳：mcr-1 / CTX-M-1 / A-ST10（1株）；CTX-M-15 / B1-ST394（3株）和CTX-M-15 / A-ST46（1株）。大多数牛ESBL-EC分离株具有多重耐药性（4/5）。