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首页> 外文期刊>Applied Microbiology >Occurrence of the Transferable Copper Resistance Gene tcrB among Fecal Enterococci of U.S. Feedlot Cattle Fed Copper-Supplemented Diets
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Occurrence of the Transferable Copper Resistance Gene tcrB among Fecal Enterococci of U.S. Feedlot Cattle Fed Copper-Supplemented Diets

机译：在美国饲喂牛饲喂铜的日粮中粪便肠球菌中存在可转移的铜抗性基因tcrB

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Copper, an essential micronutrient, is supplemented in the diet at elevated levels to reduce morbidity and mortality and to promote growth in feedlot cattle. Gut bacteria exposed to copper can acquire resistance, which among enterococci is conferred by a transferable copper resistance gene ( tcrB ) borne on a plasmid. The present study was undertaken to investigate whether the feeding of copper at levels sufficient to promote growth increases the prevalence of the tcrB gene among the fecal enterococci of feedlot cattle. The study was performed with 261 crossbred yearling heifers housed in 24 pens, with pens assigned randomly to a 2×2 factorial arrangement of treatments consisting of dietary copper and a commercial linseed meal-based energy protein supplement. A total of 22 isolates, each identified as Enterococcus faecium , were positive for tcrB with an overall prevalence of 3.8% (22/576). The prevalence was higher among the cattle fed diets supplemented with copper (6.9%) compared to normal copper levels (0.7%). The tcrB -positive isolates always contained both erm (B) and tet (M) genes. Median copper MICs for tcrB -positive and tcrB -negative enterococci were 22 and 4 mM, respectively. The transferability of the tcrB gene was demonstrated via a filter-mating assay. Multilocus variable number tandem repeat analysis revealed a genetically diverse population of enterococci. The finding of a strong association between the copper resistance gene and other antibiotic (tetracycline and tylosin) resistance determinants is significant because enterococci remain potential pathogens and have the propensity to transfer resistance genes to other bacteria in the gut.
机译：铜是必需的微量营养素，在日粮中补充了高水平的铜，以降低发病率和死亡率，并促进饲养场牛的生长。暴露于铜的肠细菌可以获得抗性，肠球菌中的这种细菌是由质粒上携带的可转移的铜抗性基因（tcrB）赋予的。进行本研究以调查以足以促进生长的水平饲喂铜是否会提高饲养场牛粪肠球菌中tcrB基因的患病率。这项研究是用261只杂交一岁小母牛组成的，这些小母牛放在24支笔中，笔随机分配给2×2因果排列的处理，包括膳食铜和基于亚麻籽粉的能量蛋白补充剂。总共22株分离株，每个被鉴定为粪肠球菌，tcrB呈阳性，总患病率为3.8％（22/576）。与铜水平正常（0.7％）相比，补充铜的牛饲喂日粮（6.9％）的患病率更高。 tcrB阳性分离株始终同时包含erm（B）和tet（M）基因。 tcrB阳性和tcrB阴性肠球菌的平均铜MIC分别为22和4 mM。 tcrB基因的可转移性已通过过滤器交配实验证明。多基因座可变数目串联重复分析揭示了肠球菌的遗传多样性。在铜抗性基因与其他抗生素（四环素和泰乐菌素）抗性决定簇之间发现有很强的联系，这很重要，因为肠球菌仍然是潜在的病原体，并且倾向于将抗性基因转移到肠道中的其他细菌。

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