Laboratoire de recherche Gestion des Ressources Animales Locales, Ecole Nationale Supérieure Vétérinaire, Oued Smar, 16000 Alger, Algérie.
Université Saad Dahlab de Blida, BP 270, Route de Soumâa, 09000 Blida, Algérie.
J Food Prot. 2020 Dec 1;83(12):2173-2178. doi: 10.4315/JFP-20-198.
The objective of this study was to investigate the occurrence of multidrug-resistant Escherichia coli in cows with clinical mastitis in 42 different dairy farms located in the Bordj Bou Arreridj region of Algeria. Milk samples were cultured on Columbia blood agar, and isolates were then identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. In total, 200 samples were screened and 52 E. coli strains confirmed as causative agents were obtained. The antimicrobial susceptibility testing was performed by disk diffusion method. Antibiotic resistance genes, including those conferring resistance to extended-spectrum β-lactamases (i.e., blaTEM, blaSHV, and blaCTX-M), tetracyclines (tetA, tetB, tetC, and tetJ), aminoglycosides [aph(3'), aac(3'), aac(6'), ant, aad, and armA], and quinolones (qnrA and qnrB) were amplified by standard PCR and sequenced when positive. Transferability of resistance genes has been investigated by conjugation experiments and multilocus sequence typing. The most frequently observed resistance was to amoxicillin (86.5%), followed by tetracycline (75%), amoxicillin-clavulanic acid (59.6%), trimethoprim-sulfamethoxazole (36.5%), doxycycline (13.5%), and ciprofloxacin (13.5%). Multidrug resistance was observed in 38.4% of isolates. Genotypic characterization showed that tetA (44.2%) and blaTEM-1 (30.7%) genes were the most prevalent. Screening for plasmid-mediated quinolone resistance genes demonstrated that seven isolates (13.5%) expressed qnrB and one isolate (1.9%) harbored qnrA. In addition, aminoglycoside resistance determinants including aadA1 and aac(3)-Id were detected in seven and two isolates, respectively. Moreover, blaTEM, tetA, tetB, qnrB, and aadA1 were successfully transferred horizontally to transconjugant strains. The multilocus sequence typing revealed the presence of three different sequence types (ST162, ST371, and ST 949).
本研究的目的是调查在阿尔及利亚博尔杰布阿尔雷德里区的 42 个不同奶牛场中患有临床乳腺炎的奶牛中多药耐药大肠杆菌的发生情况。将牛奶样本在哥伦比亚血琼脂上培养，然后通过基质辅助激光解吸电离飞行时间质谱对分离株进行鉴定。总共筛选了 200 个样本，获得了 52 株确定为病原体的大肠杆菌菌株。采用纸片扩散法进行抗菌药物敏感性试验。通过标准 PCR 扩增并测序，检测了包括对扩展谱β-内酰胺类抗生素（即 blaTEM、blaSHV 和 blaCTX-M）、四环素（tetA、tetB、tetC 和 tetJ）、氨基糖苷类[aph(3')、aac(3')、aac(6')、ant、aad 和 armA]和喹诺酮类（qnrA 和 qnrB）耐药的抗生素耐药基因。通过接合实验和多位点序列分型研究了耐药基因的可转移性。最常见的耐药现象是对阿莫西林（86.5%），其次是四环素（75%）、阿莫西林-克拉维酸（59.6%）、甲氧苄啶-磺胺甲恶唑（36.5%）、强力霉素（13.5%）和环丙沙星（13.5%）。38.4%的分离株表现出多药耐药性。基因分型表明，tetA（44.2%）和 blaTEM-1（30.7%）基因最为常见。对质粒介导的喹诺酮耐药基因的筛选表明，有 7 株（13.5%）表达 qnrB，1 株（1.9%）携带 qnrA。此外，还在 7 株和 2 株分离株中检测到了氨基糖苷类耐药决定因子 aadA1 和 aac(3)-Id。此外，blaTEM、tetA、tetB、qnrB 和 aadA1 成功地在转导子菌株中水平转移。多位点序列分型显示存在 3 种不同的序列类型（ST162、ST371 和 ST949）。
