摘要

  产肠毒素大肠杆菌（ETEC）引起猪急性分泌性腹泻，给养猪业造成巨大经济损失。本研究分析了来自有症状猪的 132 株 ETEC 分离株的原噬菌体的流行率和遗传特征，以确定它们传播抗生素耐药性的潜力。共鉴定出 1105 个潜在的原噬菌体，基因组大小的分布显示出三种“重叠”趋势。相似矩阵比较表明原噬菌体与 ETEC 谱系分布相关，进一步鉴定这些原噬菌体证实了谱系特异性。总共在132个ETEC菌株中鉴定了52个不同类别的1206个抗生素抗性基因（ARG）；其中，2.65% (32/1206) 的 ARG 被发现由原噬菌体携带。对侧翼序列的分析表明，几乎所有的 ARG 都可以分为两种类型：“blaTEM-1B”和“经典 1 类整合子（IntI1）”。它们与严格保守的重组酶和转座子 Tn3 家族共同发生，但有区别：“blaTEM-1B 型”原噬菌体表现出具有 100% 序列同一性的经典 Tn2 转座子结构，而“IntI1 型”与 TnAs2 共同发生仅具有 84% 序列同一性的转座子。这些结果意味着 ARGs 可能通过转座噬菌体的传播在天然细菌种群中普遍存在。

   Enterotoxigenic Escherichia coli (ETEC) cause acute secretory diarrhoea in pigs, posing a great economic loss to the swine industry. This study analysed the prevalence and genetic characteristics of prophages from 132 ETEC isolates from symptomatic pigs to determine their potential for spreading antibiotic resistance. A total of 1105 potential prophages were identified, and the distribution of the genome size showed three ‘overlapping’ trends. Similarity matrix comparison showed that prophages correlated with the ETEC lineage distribution, and further identification of these prophages corroborated the lineage specificity. In total, 1206 antibiotic resistance genes (ARGs) of 52 different categories were identified in 132 ETEC strains; among these, 2.65% (32/1206) of ARGs were found to be carried by prophages. Analysis of flanking sequences showed that almost all the ARGs could be grouped into two types: ‘blaTEM-1B’ and ‘classic class 1 integron (IntI1)’. They co-occurred with a strictly conserved recombinase and transposon Tn3 family but with a difference: the ‘blaTEM-1B type’ prophages exhibited a classic Tn2 transposon structure with 100% sequence identity, whereas the ‘IntI1 type’ co-occurred with the TnAs2 transposon with only 84% sequence identity. These results imply that ARGs might be pervasive in natural bacterial populations through transmission by transposable bacteriophages.

   https://sfamjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1462-2920.15084