Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada.
Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada.
J Dairy Sci. 2018 Apr;101(4):3271-3284. doi: 10.3168/jds.2017-13277. Epub 2018 Feb 7.
This study was carried out to determine the frequency of fecal carriage, antimicrobial susceptibility, and resistance genes in Salmonella enterica and Escherichia coli with reduced susceptibility to extended-spectrum cephalosporins (ESC) isolated from 488 dairy calves from 8 farms in New Brunswick, Canada. Both S. enterica and E. coli with reduced susceptibility to ESC were isolated using selective culture. Minimum inhibitory concentrations to a panel of antimicrobial drugs were determined for randomly selected E. coli isolates and all of the Salmonella isolates. Multiplex PCR were conducted on the selected ESC-resistant E. coli to assess the β-lactamase resistance genes (bla, bla, bla, and bla) and plasmid-mediated qnrB and qnrS resistant genes. Information on ceftiofur use and other farm management practices were collected by the use of a questionnaire to determine the risk factors for the fecal recovery of E. coli with reduced susceptibility to ESC. Salmonella enterica frequency in calves' fecal samples was 3.3%, and all were pansusceptible. Salmonella isolates belonged to 3 serovars namely Salmonella Senftenberg, Salmonella Typhimurium, and Salmonella Derby. The frequency of fecal carriage of E. coli with reduced susceptibility to ESC in calves was 81.2%. Of the selected isolates (n = 100), all were multi-drug resistant, whereas 88% were ESC resistant based on minimum inhibitory concentration testing. From the selected ESC-resistant E. coli isolates, bla was detected in 84.1%, bla was detected in 52.2%, bla groups were detected in 30.7%, and bla was detected in 1.1% of isolates. Plasmid-mediated quinolone resistance genes were identified in 7 of 9 isolates resistant to quinolones. Five isolates were positive for qnrB, whereas 2 isolates were positive for both qnrB and qnrS. Whereas neonatal calves [odds ratio (OR) = 2.42, 95% confidence interval (CI): 1.87-3.12], regular ceftiofur use on the farm (OR = 3.83, 95% CI: 2.29-6.39), feeding of unpasteurized nonsalable milk (OR = 1.6, 95% CI: 1.18-2.18), and use of florfenicol (OR = 2.02, 95% CI: 1.43-2.86) were statistically associated with fecal recovery of E. coli with reduced susceptibility to ESC, use of ceftiofur for the treatment of respiratory diseases (OR = 0.57, 95% CI: 0.41-0.79) was statistically associated with decreased recovery of E. coli with reduced susceptibility to ESC. This study has provided information on the resistance genes associated with the occurrence of ESC and fluoroquinolone resistance in dairy calves within this region.
本研究旨在确定加拿大新不伦瑞克省 8 个农场的 488 头奶牛粪便中携带、对扩展谱头孢菌素（ESC）敏感性降低的沙门氏菌和大肠埃希菌的频率，以及这些 ESC 耐药大肠埃希菌的抗生素药敏性、耐药基因和质粒介导的 qnrB 和 qnrS 耐药基因。使用选择性培养基分离对 ESC 敏感性降低的沙门氏菌和大肠埃希菌。随机选择的大肠埃希菌分离株和所有沙门氏菌分离株的最小抑菌浓度（MIC）用药敏试验确定。对选择的 ESC 耐药大肠埃希菌进行多重 PCR，以评估β-内酰胺酶耐药基因（bla、bla、bla 和 bla）和质粒介导的 qnrB 和 qnrS 耐药基因。通过使用问卷收集有关头孢噻呋使用和其他农场管理实践的信息，以确定对 ESC 敏感性降低的大肠埃希菌粪便恢复的危险因素。犊牛粪便中沙门氏菌的频率为 3.3%，且均为泛敏感型。沙门氏菌分离株属于 3 个血清型，即肠炎沙门氏菌、鼠伤寒沙门氏菌和德尔比沙门氏菌。对 ESC 敏感性降低的大肠埃希菌在犊牛粪便中的携带率为 81.2%。在所选择的分离株（n=100）中，所有分离株均为多药耐药株，而根据 MIC 检测，88%为 ESC 耐药株。从选择的 ESC 耐药大肠埃希菌分离株中，84.1%检测到 bla，52.2%检测到 bla，30.7%检测到 bla 组，1.1%检测到 bla。在对喹诺酮类药物耐药的 9 株分离株中，有 7 株检测到质粒介导的喹诺酮耐药基因。5 株分离株对 qnrB 阳性，2 株分离株对 qnrB 和 qnrS 均阳性。新生犊牛（比值比（OR）=2.42，95%置信区间（CI）：1.87-3.12）、农场常规使用头孢噻呋（OR=3.83，95%CI：2.29-6.39）、饲喂未经巴氏消毒的非销售牛奶（OR=1.6，95%CI：1.18-2.18）和使用氟苯尼考（OR=2.02，95%CI：1.43-2.86）与 ESC 敏感性降低的大肠埃希菌粪便恢复呈统计学相关，而头孢噻呋用于治疗呼吸道疾病（OR=0.57，95%CI：0.41-0.79）与 ESC 敏感性降低的大肠埃希菌粪便恢复呈统计学相关。本研究提供了有关该地区奶牛携带 ESC 和氟喹诺酮耐药相关耐药基因的信息。
