意图
本研究的目的是研究阿莫西林（β-内酰胺）和氯霉素（氯霉素）给药对鸡肠道中抗微生物耐药性基因（ARGs）丰度的选择性压力。
方法和材料
将18只肉鸡分为三组，在5日龄时不经处理或用阿莫西林或硫酚处理连续饲养三天。从所有1日龄的鸟身上采集泄殖腔拭子作为参考，然后在第8、19和28天采集。在饲养周期结束时，对鸟类进行屠宰，并无菌收集盲肠内容物。拭子（n = 72）和盲肠内容物（n = 13） 通过定量PCR测定进行分析，以产生关于对β-内酰胺产生耐药性的14个ARG的丰度的数据（n = 8） 和酚类化合物（n = 6). 使用Friedmann检验和Dunn检验进行多重比较，评估同一组内ARGs丰度随时间点的差异，而Spearmann秩相关用于评估β-内酰胺和氯霉素ARGs的共存。
后果
在用阿莫西林或噻mphenicol治疗的组中观察到赋予对氯霉素抗性的ARGs的丰度增加（p＜0.05），两种抗菌药物治疗后21天，floR和cmlA基因的丰度显著增加（p＜0.05）。阿莫西林治疗后1天，blaSHV的丰度增加（p＞0.05） = 0.245）和cmlA（p＜0.0001；r = 0.325）。
结论
研究结果似乎表明，在阿莫西林和氯霉素施加的选择性压力下，赋予β-内酰胺耐药性的blaTEM-1以及赋予氯霉素耐药性的cmlA和floR的丰度呈增加趋势。
Purpose
the aim of the study was to investigate the selective pressure exerted by amoxicillin (beta-lactam) and thiamphenicol (phenicol) administration on the abundance of antimicrobial resistance genes (ARGs) in the chicken gut.

Methods & Materials
eighteen broiler chicks were allocated in three groups and reared without treatment or treated with either amoxicillin or thiamphenicol at 5 days of age for three consecutive days. Cloacal swabs were taken from all birds at 1 day of age, as reference, and then on days 8, 19, and 28. At the end of the rearing cycle, birds were slaughtered and the caecal content was aseptically collected. Swabs (n = 72) and caecal contents (n = 13) were analysed by quantitative PCR assays to generate data on the abundance of fourteen ARGs conferring resistance to beta-lactams (n = 8) and phenicols (n = 6). Difference in ARGs abundance over time points within the same group was assessed using Friedmann test with Dunn's test for multiple comparisons, while Spearmann's rank correlation was used to assess the co-occurrence of beta-lactam and phenicol ARGs.

Results
increased abundance of ARGs conferring resistance to phenicols was observed in the groups treated with either amoxicillin or thiamphenicol (p < 0.05). In detail, the abundance of floR and cmlA genes was significantly increased (p < 0.05) after treatment with either of the two antimicrobials up to 21 days post-treatment (d.p.t.). Amoxicillin treatment enhanced the abundance of blaSHV at 1 d.p.t. (p < 0.05). Positive correlations between blaTEM-1 and floR (p < 0.05; r = 0.245) and cmlA (p < 0.0001; r = 0.325) were also observed.

Conclusion
the results of the study seem to suggest an increasing trend of abundance of blaTEM-1, conferring resistance to beta-lactams, and cmlA and floR, conferring resistance to phenicols, under the selective pressure exerted by amoxicillin and phenicols.

https://www.sciencedirect.com/science/article/pii/S1201971221009073