Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.
Guelph Research and Development Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada N1G 5C9.
J Food Prot. 2021 Aug 1;84(8):1385-1399. doi: 10.4315/JFP-21-033.
This study was conducted to investigate the effects of in-feed encapsulated cinnamaldehyde (CIN) and citral (CIT) alone or in combination on antimicrobial resistance (AMR) phenotypes and genotypes of Escherichia coli isolates recovered from feces of 6-, 16-, 23-, and 27-day-old broiler chickens. The five dietary treatments including the basal diet (negative control [NC]) and the basal diet supplemented with 55 ppm of bacitracin (BAC), 100 ppm of encapsulated CIN, 100 ppm of encapsulated CIT, or 100 ppm each of encapsulated CIN and encapsulated CIT (CIN+CIT). Antimicrobial susceptibility testing of 240 E. coli isolates revealed that the most common resistance was to β-lactams, aminoglycosides, sulfonamides, and tetracycline; however, the prevalence of AMR decreased (P < 0.05) as birds aged. The prevalence of resistance to amoxicillin-clavulanic acid, ceftiofur, ceftriaxone, cefoxitin, gentamicin, and sulfonamide was lower (P < 0.05) in isolates from the CIN or CIN+CIT groups than in isolates from the NC or BAC groups. Whole genome sequencing of 227 of the 240 isolates revealed 26 AMR genes and 19 plasmids, but the prevalence of some AMR genes and the number of plasmids were lower (P < 0.05) in E. coli isolated from CIN or CIN+CIT birds than in isolates from NC or BAC birds. The most prevalent resistance genes were tet(A) (108 isolates), aac(3)-VIa (91 isolates), aadA1 (86 isolates), blaCMY-2 (78 isolates), sul1 (77 isolates), aph(3)-Ib (58 isolates), aph(6)-Id (58 isolates), and sul2 (24 isolates). The numbers of most virulence genes carried by isolates increased (P < 0.05) in chickens from 6 to 27 days of age. The prevalence of E. coli O21:H16 isolates was lower (P < 0.05) in CIN and CIN+CIT, and the colibacillosis-associated multilocus sequence type (ST117) was most prevalent in isolates from 23-day-old chickens. A phylogenetic tree of whole genome sequences revealed a close relationship between 25 of the 227 isolates and human or broiler extraintestinal pathogenic E. coli strains. These findings indicate that AMR and virulence genotypes of E. coli could be modulated by providing encapsulated CIN or CIN+CIT feed supplements, but further investigation is needed to determine the mechanisms of the effects of these supplements.
本研究旨在调查饲料中添加包被肉桂醛（CIN）和柠檬醛（CIT）单独或联合对 6、16、23 和 27 日龄肉鸡粪便中分离的大肠杆菌的抗菌药物耐药性表型和基因型的影响。五种日粮处理包括基础日粮（阴性对照[NC]）和基础日粮添加 55ppm 杆菌肽（BAC）、100ppm 包被肉桂醛、100ppm 包被柠檬醛或 100ppm 包被肉桂醛和包被柠檬醛（CIN+CIT）。对 240 株大肠杆菌的药敏试验表明，最常见的耐药性是β-内酰胺类、氨基糖苷类、磺胺类和四环素类；然而，随着禽类年龄的增长，抗菌药物耐药性的流行率降低（P<0.05）。来自 CIN 或 CIN+CIT 组的分离株对阿莫西林-克拉维酸、头孢噻呋、头孢曲松、头孢西丁、庆大霉素和磺胺类药物的耐药率较低（P<0.05），而来自 NC 或 BAC 组的分离株则较高。对 240 株分离株中的 227 株进行全基因组测序显示，存在 26 种抗菌药物耐药基因和 19 种质粒，但来自 CIN 或 CIN+CIT 组的大肠杆菌分离株中某些抗菌药物耐药基因和质粒的流行率较低（P<0.05），而来自 NC 或 BAC 组的分离株则较高。最常见的耐药基因是 tet(A)（108 株）、aac(3)-VIa（91 株）、aadA1（86 株）、blaCMY-2（78 株）、sul1（77 株）、aph(3)-Ib（58 株）、aph(6)-Id（58 株）和 sul2（24 株）。6 至 27 日龄鸡分离株携带的大多数毒力基因数量增加（P<0.05）。CIN 和 CIN+CIT 组中 O21:H16 分离株的流行率较低（P<0.05），而与大肠杆菌病相关的多位点序列型（ST117）在 23 日龄鸡分离株中最为流行。全基因组序列系统发育树显示，227 株分离株中有 25 株与人类或肉鸡肠外致病性大肠杆菌菌株密切相关。这些发现表明，提供包被肉桂醛或 CIN+CIT 饲料补充剂可以调节大肠杆菌的抗菌药物耐药性和毒力基因型，但需要进一步研究以确定这些补充剂的作用机制。
