The true prevalence of tet(A), which codes for a tetracycline efflux pump, in thermophilic Camplyobacter spp. requires clarification after reports emerged in Iran (2014) and Kenya (2016) of the novel detection of tet(A) in Campylobacter. During our investigation of antibiotic resistance mechanisms in a sample of Irish thermophilic Campylobacter broiler isolates, it was determined that 100% of tetracycline-resistant isolates (n = 119) harboured tet(O). Accessory tetracycline-resistance mechanisms were considered as tetracycline minimum inhibitory concentrations ranged from 4 to ≥ 64 mg/L. Primers previously reported for the detection of tet(A) in Campylobacter failed to produce an amplicon using a positive control strain (Escherichia coli K12 SK1592 containing the pBR322 plasmid) and a selection of Campylobacter isolates. Accordingly, we designed new tet(A)-targeting primers on SnapGene2.3.2 that successfully generated a 407 bp product from the positive control strain only. Further in silico analysis using BLASTn and SnapGene2.3.2 revealed that previously reported Campylobacter tet(A) sequences deposited on GenBank shared 100% homology with Campylobacter tet(O). We postulate that this gave rise to the erroneous report of a high tet(A) prevalence among a pool of Kenyan broiler Campylobacter isolates that were tested using primers designed based on these apparent tet(A) sequences. In conclusion, further work would be required to determine whether the homology between tet(A) potentially present in Campylobacter and known tet(A) genes would be sufficient to allow amplification using the primers designed in our study. Finally, the existence of tet(A) in thermophilic Campylobacter spp. remains to be demonstrated.

中文翻译：

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嗜热弯曲杆菌属中四环素抗性的分子机制研究。提示先前关于这些细菌中tet（A）介导的抗性的报道为时过早。

tet（A）在嗜热弯曲杆菌属中的真实流行，其编码四环素外排泵。在伊朗（2014年）和肯尼亚（2016年）出现关于弯曲杆菌中新型tet（A）检测的报道后，需要澄清。在我们对爱尔兰嗜热弯曲杆菌肉鸡分离株样品的抗生素抗性机制进行调查期间，确定100％的四环素抗性分离株（n = 119）带有tet（O）。辅助四环素抗性机制被认为是四环素的最低抑菌浓度范围为4至≥64 mg / L。先前报道的用于检测弯曲杆菌中tet（A）的引物无法使用阳性对照菌株（含有pBR322质粒的大肠杆菌K12 SK1592）和选择弯曲杆菌分离株来产生扩增子。因此，我们在SnapGene2.3.2上设计了新的靶向tet（A）的引物，仅从阳性对照菌株成功产生了407 bp的产物。使用BLASTn和SnapGene2.3.2进行的进一步计算机分析表明，先前报道的保存在GenBank中的弯曲杆菌tet（A）序列与弯曲杆菌tet（O）具有100％的同源性。我们假设这引起了错误的报道，即使用基于这些明显的tet（A）序列设计的引物测试了肯尼亚肉鸡弯曲杆菌分离株中的高tet（A）患病率。总之，将需要进一步的工作来确定弯曲杆菌中可能存在的tet（A）与已知tet（A）基因之间的同源性是否足以使用本研究设计的引物进行扩增。最后，嗜热弯曲杆菌属中tet（A）的存在。有待证明。