| Affiliation: | 1. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, 50011 USA Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642 China;2. Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642 China;3. State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, 150069 China;4. Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, 50011 USA |
| Abstract: | 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. |
