Department of Population Medicine and Diagnostic Sciences. College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
J Dairy Sci. 2011 Sep;94(9):4556-65. doi: 10.3168/jds.2011-4337.
Diarrhea in calves has a significant effect on the dairy industry. A common management practice for preventing or decreasing the effects of such disease in preweaned calves is by the use of antimicrobials in milk or milk replacer. In this study, Escherichia coli antimicrobial resistance in fecal samples collected from calves 2 to 8 d of age that had or had not received antimicrobials in the milk and that had or had not signs of diarrhea by inspection of fecal consistency were investigated. Specifically, resistance of E. coli isolates to individual antimicrobials, multiresistance patterns, and presence of virulence factors were analyzed. Escherichia coli isolates were tested for susceptibility to 12 antimicrobials by use of a Kirby-Bauer disk diffusion assay. The study was conducted at 3 farms, 1 administering growth-promoting antimicrobials (GPA) in the milk and 2 not using GPA in the milk (NGPA). All isolates were susceptible to ciprofloxacin and cefepime. From the total isolates tested, 84% (n=251) were resistant to at least 2 antimicrobials and 81% (n=251) were resistant to 3 or more antimicrobials. When antimicrobial resistance was compared between GPA and NGPA, it was observed that the GPA group had higher odds of antimicrobial resistance for most of the individual antimicrobials tested. No significant correlation of virulence factors in GPA or NGPA and diarrheic or non-diarrheic (control) fecal samples was found. Of the 32 virulence factors evaluated, 21 were detected in the study population; the incidence of only 1 virulence factor was statistically significant in each of the diarrheic status (diarrheic or non-diarrheic) and treatment status (NGPA or GPA) groups. Phylogenetic analysis based on the nucleotide sequence of the DNA gyrase gene (gyrB) from 31 fecal E. coli isolates revealed 3 main clades.
犊牛腹泻对奶牛养殖业有重大影响。在哺乳期前预防或减少犊牛此类疾病影响的常见管理措施是在牛奶或代乳中使用抗生素。在这项研究中，研究了在哺乳期接受或未接受抗生素且粪便稠度检查无腹泻或有腹泻迹象的 2 至 8 日龄犊牛粪便样本中收集的大肠杆菌的抗菌药物耐药性。具体而言，分析了大肠杆菌分离株对单个抗菌药物的耐药性、多重耐药模式和毒力因子的存在。使用 Kirby-Bauer 纸片扩散法测定大肠杆菌分离株对 12 种抗菌药物的敏感性。该研究在 3 个农场进行，其中 1 个农场在牛奶中添加促生长抗生素（GPA），2 个农场不在牛奶中添加 GPA（NGPA）。所有分离株均对环丙沙星和头孢吡肟敏感。在测试的总分离株中，84%（n=251）至少对 2 种抗菌药物耐药，81%（n=251）对 3 种或更多种抗菌药物耐药。当比较 GPA 和 NGPA 之间的抗菌药物耐药性时，观察到 GPA 组对大多数测试的单个抗菌药物的耐药性几率更高。在 GPA 或 NGPA 中，未发现毒力因子与腹泻或非腹泻（对照）粪便样本之间存在显著相关性。在评估的 32 种毒力因子中，研究人群中检测到 21 种；在腹泻状态（腹泻或非腹泻）和治疗状态（NGPA 或 GPA）组中，每种毒力因子的发生率都有统计学意义。基于 31 株粪便大肠杆菌的 DNA 拓扑异构酶基因（gyrB）核苷酸序列的系统发育分析显示了 3 个主要分支。
