College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, 210095, P. R. China.
Key lab of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing, 210095, P. R. China.
J Microbiol. 2017 Sep;55(9):703-710. doi: 10.1007/s12275-017-6241-x. Epub 2017 Sep 2.
In China, antimicrobials and copper are used extensively as growth-promoting agents for piglets. This study aimed to characterize the role of in-feed copper in the emergence of copper-tolerant and antibiotic-resistant Enterococcus and Lactobacillus isolates in Chinese pig farms. Feces of the same eight piglets from four litters at 7 and 55 days old and their mothers were traced in order to isolate Enterococcus spp. and Lactobacillus spp.. The minimum inhibitory concentrations of 10 antimicrobials and copper sulfate were determined using an agar dilution method. The feed levels of Cu for lactating sows, suckling piglets, and weaned piglets were 6, 177, and 18 mg/kg, respectively. All the 136 Enterococcus isolates were sensitive to vancomycin; and the resistance rates to penicillin, enrofloxacin, and high level streptomycin resistance increased significantly after weaning. For the 155 Lactobacillus isolates, the resistance rates to ampicillin, chloramphenicol, tetracycline, and enrofloxacin were significantly higher in weaned piglets. The ratios of copper tolerant Enterococcus and Lactobacillus isolates both increased significantly after weaning (P < 0.05). A phenotypic correlation was observed after classifying the isolates into two groups (CuSO MIC < 16 or ≧16 for enterococci; CuSO MIC < 12 or ≧12 for lactobacilli) and comparing the antimicrobial-resistant percentage of two groups. On species level, a significant increase of E. faecalis to enrofloxacin was observed in line with the increase of copper MIC (P < 0.05). The findings revealed the changes of the antibiotic resistance and copper tolerance level of enterococci and lactobacilli between suckling and weaned piglets and demonstrated that there might be a strong association between in-feed copper and increased antibiotic resistance in enterococci and lactobacilli in Chinese intensive swine farms.
在中国，抗生素和铜被广泛用作仔猪的促生长剂。本研究旨在描述饲料中添加铜对中国猪场出现耐铜和耐抗生素粪肠球菌和乳酸杆菌的作用。对来自四个窝的同一 8 头仔猪及其母畜的粪便进行追踪，以分离粪肠球菌和乳酸杆菌。采用琼脂稀释法测定 10 种抗生素和硫酸铜的最小抑菌浓度。哺乳期母猪、哺乳仔猪和断奶仔猪的饲料铜水平分别为 6、177 和 18mg/kg。所有 136 株肠球菌分离株均对万古霉素敏感；断奶后，对青霉素、恩诺沙星和高水平链霉素的耐药率显著增加。对于 155 株乳酸杆菌分离株，在断奶仔猪中，对氨苄西林、氯霉素、四环素和恩诺沙星的耐药率显著升高。耐铜粪肠球菌和乳酸杆菌分离株的比例在断奶后均显著增加（P<0.05）。将分离株分为两组（铜硫酸盐 MIC<16 或≧16 用于肠球菌；铜硫酸盐 MIC<12 或≧12 用于乳酸杆菌），并比较两组的抗生素耐药百分比，观察到表型相关性。在种水平上，随着铜 MIC 的增加，粪肠球菌对恩诺沙星的耐药性显著增加（P<0.05）。研究结果揭示了哺乳仔猪和断奶仔猪之间肠球菌和乳酸杆菌的抗生素耐药性和铜耐受性水平的变化，并表明中国集约化猪场饲料中添加铜与肠球菌和乳酸杆菌的抗生素耐药性增加之间可能存在很强的关联。
