Food and Feed Safety Research Unit, Southern Plains Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, College Station, Texas 77845, USA.
Foodborne Pathog Dis. 2011 Mar;8(3):395-401. doi: 10.1089/fpd.2010.0686.
The objectives of the current research were to determine the effect of weaning on fecal shedding of Salmonella and Escherichia coli O157:H7 in dairy calves and to examine cultured isolates (to include Enterococcus) for antimicrobial susceptibility. This research was conducted on one large commercial dairy (>3000 head) in the southwestern United States. Two collections were made, during the winter (January 2009) and summer (July 2009) seasons. For the winter collection, two groups of calves were sampled (group 1: n = 18 pens, 69 head, ∼12 weeks of age; group 2: n = 19 pens, 75 head, ∼10 weeks of age). Fecal samples were collected from all calves via rectal palpation 2 days pre- and again 2 days postweaning. For the summer collection, one group of calves housed in 40 pens were utilized and 79 and 76 calves sampled 7 days pre- and 5 days postweaning, respectively. Fecal samples were collected into sterile palpation sleeves, placed on ice, and shipped to our laboratory for bacterial culture of E. coli O157:H7, Salmonella, and Enterococcus. Antimicrobial susceptibility was determined on select isolates. No differences (p > 0.10) in prevalence of Salmonella or E. coli O157:H7 were observed due to weaning in the winter collection. In the summer collection, more (p < 0.01) fecal samples were Salmonella positive preweaning (15.2%) as compared to postweaning (2.6%). No differences were observed for antimicrobial susceptibility in isolates collected pre- as compared to postweaning in either winter or summer collections, with the exception that multidrug-resistant Enterococcus faecium isolates preweaning were resistant to six antibiotics compared to seven or eight antibiotics postweaning (summer collection). Results of the current research indicate that the weaning of dairy calves does not increase the prevalence of pathogenic bacteria or substantially modify antimicrobial susceptibility profiles of these bacteria.
本研究的目的是确定断奶对犊牛粪便中沙门氏菌和大肠杆菌 O157:H7 脱落的影响，并检测培养分离物（包括肠球菌）的抗菌敏感性。这项研究是在美国西南部的一个大型商业奶牛场（超过 3000 头）进行的。在冬季（2009 年 1 月）和夏季（2009 年 7 月）进行了两次采集。对于冬季采集，对两组犊牛进行了采样（第 1 组：n = 18 个栏，69 头，约 12 周龄；第 2 组：n = 19 个栏，75 头，约 10 周龄）。在断奶前 2 天和断奶后 2 天，通过直肠触诊从所有犊牛中采集粪便样本。对于夏季采集，利用 40 个栏中的一组犊牛，分别在断奶前 7 天和 5 天对 79 头和 76 头犊牛进行采样。采集粪便样本放入无菌触诊套管中，置于冰上，然后运往我们的实验室进行大肠杆菌 O157:H7、沙门氏菌和肠球菌的细菌培养。选择分离株进行抗菌敏感性测定。冬季采集时，断奶对沙门氏菌或大肠杆菌 O157:H7 的流行率没有差异（p > 0.10）。在夏季采集时，断奶前（15.2%）粪便样本中沙门氏菌阳性的比例高于断奶后（2.6%）（p < 0.01）。无论是在冬季还是夏季采集，断奶前后采集的分离物在抗菌敏感性方面没有差异，除了冬季采集的多药耐药屎肠球菌分离物断奶前对六种抗生素耐药，而断奶后对七种或八种抗生素耐药（夏季采集）。本研究结果表明，犊牛断奶不会增加致病菌的流行率，也不会显著改变这些细菌的抗菌敏感性谱。
