Peeters L E J, De Mulder T, Van Coillie E, Huygens J, Smet A, Daeseleire E, Dewulf J, Imberechts H, Butaye P, Haesebrouck F, Croubels S, Heyndrickx M, Rasschaert G
Department of General Bacteriology, Veterinary and Agrochemical Research centre, Brussels, Belgium.
Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Merelbeke, Belgium.
J Appl Microbiol. 2017 Nov;123(5):1312-1320. doi: 10.1111/jam.13561. Epub 2017 Oct 9.
The aim of this study was to investigate the effect of subtherapeutic intestinal doxycycline (DOX) concentrations (4 and 1 mg l ), caused by cross-contamination of feed, on the enrichment of a DOX-resistant commensal Escherichia coli and its resistance plasmid in an ex vivo model of the porcine caecum.
A DOX-resistant, tet(A)-carrying, porcine commensal E. coli strain (EC 682) was cultivated for 6 days in the porcine caecum model under different conditions (0, 1 and 4 mg l DOX). EC 682, other coliforms and anaerobic bacteria were enumerated daily. A selection of isolated DOX-resistant coliforms (n = 454) was characterized by rep-PCR clustering, PCR assays (Inc1 and tet(A)) and micro broth dilution susceptibility tests (Sensititre). Both 1 and 4 mg l DOX-enriched medium had a significantly higher selective effect on EC 682 and other resistant coliforms than medium without DOX. Transconjugants of EC 682 were isolated more frequently in the presence of 1 and 4 mg l DOX compared to medium without DOX.
Subtherapeutic intestinal DOX concentrations have the potential to select for DOX-resistant E. coli, and promote the selection of transconjugants in a porcine caecum model.
Cross-contamination of feed with antimicrobials such as DOX likely promotes the spread of antimicrobial resistance. Therefore, it is important to develop or fine-tune guidelines for the safe use of antimicrobials in animal feed and its storage.
本研究旨在探讨饲料交叉污染导致的亚治疗浓度肠道强力霉素（DOX）（4和1毫克/升）对猪盲肠体外模型中耐DOX共生大肠杆菌及其耐药质粒富集的影响。
携带tet(A)的耐DOX猪共生大肠杆菌菌株（EC 682）在不同条件（0、1和4毫克/升DOX）下的猪盲肠模型中培养6天。每天对EC 682、其他大肠菌群和厌氧菌进行计数。通过rep-PCR聚类、PCR检测（Inc1和tet(A)）和微量肉汤稀释药敏试验（Sensititre）对选择的分离耐DOX大肠菌群（n = 454）进行表征。与不含DOX的培养基相比，1和4毫克/升DOX富集培养基对EC 682和其他耐药大肠菌群具有显著更高的选择作用。与不含DOX的培养基相比，在1和4毫克/升DOX存在的情况下，EC 682的接合子更频繁地被分离出来。
亚治疗浓度的肠道DOX有选择耐DOX大肠杆菌的潜力，并促进猪盲肠模型中接合子的选择。
饲料被DOX等抗菌药物交叉污染可能会促进抗菌药物耐药性的传播。因此，制定或微调动物饲料及其储存中抗菌药物安全使用的指南非常重要。
