Quantification of the BlaCMY-2 in Feces from Beef Feedlot Cattle Administered Three Different Doses of Ceftiofur in a Longitudinal Controlled Field Trial
Quantification of the BlaCMY-2 in Feces from Beef Feedlot Cattle Administered Three Different Doses of Ceftiofur in a Longitudinal Controlled Field Trial
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DOI：
10.1089/fpd.2009.0271
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发表时间：
2009-10-01
影响因子：
2.8
通讯作者：
Loneragan, G. H.
中科院分区：
文献类型：
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作者：
Alali, W. Q.;Scott, H. M.;Loneragan, G. H.
本纵向对照试验的目的是定量比较从接受三种不同剂量方案头孢噻呋结晶游离酸（CCFA）治疗的牛与未接受治疗的牛（对照）采集的粪便样本中提取的总群落DNA中编码头孢噻呋耐药基因（bla（CMY-2））的携带情况，标准化为参考基因（16 SrRNA）。将61头阉牛分配至3种治疗方案，并圈养在6个畜栏中。在每个畜栏中，5头阉牛接受治疗，5头为对照（其中一个畜栏有6头对照）。CCFA给药如下：三分之二剂量给药（4.4 mg/kg，第0天）、单次给药（6.6 mg/kg，第0天）和三次给药（6.6 mg/kg，第0、6和13天）。在第0、3、7、10、14、18、21和28天收集粪便样品。使用定量实时PCR在总群落DNA样品中测定bla（CMY-2）和16 SrRNA的基因拷贝数/克粪便。使用重复测量混合模型评估标准化bla（CMY-2）、非标准化bla（CMY-2）和非标准化16 SrRNA的数量与解释变量（治疗、时间和治疗x时间）之间的关系。有显着差异，在每一个三个模型就每个解释变量。总体而言，虽然给予三个剂量和三分之二剂量的CCFA的阉牛的非标准化bla（CMY-2）量显著高于对照组，但标准化值较低。在饲养场牛中给予CCFA可能提供有利于较高bla（CMY-2）携带水平的选择压力，但这也可能导致给药期间总细菌种群同时减少（如16 SrRNA降低所反映）。
The objective of this longitudinal controlled trial was to quantitatively compare carriage of a gene encoding for ceftiofur-resistance (bla(CMY-2)), standardized to a reference gene (16SrRNA), among total community DNA extracted from fecal samples collected from cattle treated with three different dose regimens of ceftiofur crystalline-free acid (CCFA) versus those untreated (controls). Sixty-one steers were assigned to three treatment regimens and housed in six pens. In each pen, five steers were treated and five were controls (one of the pens had six controls). CCFA administration was as follows: two-thirds dose treatment (4.4 mg/kg, on day 0), single-dose treatment (6.6 mg/kg, on day 0), and three-dose treatment (6.6 mg/kg, on days 0, 6, and 13). Fecal samples were collected on days 0, 3, 7, 10, 14, 18, 21, and 28. The gene copy numbers/gram of feces for bla(CMY-2) and 16SrRNA were determined in total community DNA samples using quantitative real-time PCR. The relationships between the quantities of standardized bla(CMY-2), nonstandardized bla(CMY-2), and nonstandardized 16SrRNA, and the explanatory variables (treatment, time, and treatment x time) were assessed using repeated measures mixed models. There were significant differences in each of the three models with respect to each explanatory variable. Overall, while steers administered three doses and two-thirds dose of CCFA had significantly higher quantities of nonstandardized bla(CMY-2) than controls, the standardized values were lower. The administration of CCFA in feedlot cattle may provide selection pressure favoring higher levels of bla(CMY-2) carriage, but this may also lead to concurrent reductions in the total bacterial population (as reflected by lowered 16SrRNA) during the treatment period.