Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Veterinary Medicine, China Agricultural University, Beijing, China.
College of Animal Science and Veterinary Medicine, Henan Agricultural University, Zhengzhou, China.
Environ Int. 2019 Jun;127:361-370. doi: 10.1016/j.envint.2019.03.061. Epub 2019 Apr 4.
The extensive use of colistin in swine production may have contributed to the recent emergence of corresponding mobile resistance gene mcr-1. The use of colistin as a feed additive was banned in China in April 2017.
To examine the occurrence of colistin and dissemination of mcr-1 in swine feedlots before and after the colistin ban and effects of different manure treatments.
Environmental samples were collected from swine feedlots before (December 2016) and after (December 2017) the colistin ban. Colistin concentrations were determined by ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The prevalence of mcr-1 were determined by quantitative PCR analysis, while bacterial community composition was investigated by 16S rRNA sequencing.
In 2016, colistin was detected in feed and fresh manure samples at 67 mg/kg and 17 mg/kg, respectively, but was absent from all samples in 2017. In 2016, the relative abundance of mcr-1 in fresh manure was lower than that in solid samples after natural drying, while a higher relative abundance was detected in fresh manure samples compared with biogas slurry samples. A strong correlation between colistin concentration and relative abundance of mcr-1 was observed in fresh manure. The samples collected in 2017 showed a lower relative abundance of mcr-1 compared with those collected in 2016. Bacterial community analysis showed that the abundance of Enterobacteriaceae, which act as a vehicle and reservoir of mcr-1, increased with natural dying but decreased with anaerobic digestion.
The presence of colistin exerts direct selection pressure for the accumulation of mcr-1 in manure, while the ban on colistin likely halted the dissemination of mcr-1 on pig farms. Anaerobic digestion is an effective waste treatment process for removing mcr-1, which might be mainly driven by the shift in bacterial community structure.
黏菌素在猪生产中的广泛应用可能导致了最近相应的移动耐药基因 mcr-1 的出现。中国已于 2017 年 4 月禁止将黏菌素用作饲料添加剂。
在黏菌素禁令实施前后，检测猪养殖场中黏菌素的使用情况和 mcr-1 的传播情况，并评估不同粪便处理方式的影响。
在黏菌素禁令实施前后（2016 年 12 月和 2017 年 12 月），从猪养殖场采集环境样本。采用超高效液相色谱-串联质谱法测定黏菌素浓度。通过定量 PCR 分析检测 mcr-1 的流行情况，通过 16S rRNA 测序分析细菌群落组成。
2016 年，饲料和新鲜粪便样本中分别检出 67mg/kg 和 17mg/kg 的黏菌素，但 2017 年所有样本中均未检出。2016 年，新鲜粪便中 mcr-1 的相对丰度低于自然干燥后的固体样本，但高于沼气渣样本。新鲜粪便中黏菌素浓度与 mcr-1 相对丰度之间存在较强的相关性。与 2016 年相比，2017 年采集的样本 mcr-1 相对丰度较低。细菌群落分析显示，作为 mcr-1 载体和储存库的肠杆菌科的丰度随着自然干燥而增加，随着厌氧消化而减少。
黏菌素的存在对粪便中 mcr-1 的积累施加了直接的选择压力，而黏菌素禁令可能阻止了 mcr-1 在猪场的传播。厌氧消化是一种有效的粪便处理工艺，可有效去除 mcr-1，其可能主要受到细菌群落结构变化的驱动。
