Mathew Alan G, Arnett Debbie B, Cullen Patricia, Ebner Paul D
Department of Animal Science, University of Tennessee, 2505 River Drive, Knoxville, TN 37996, USA.
Int J Food Microbiol. 2003 Dec 15;89(1):11-20. doi: 10.1016/s0168-1605(03)00124-7.
Weaned pigs were separated into eight treatments including a control without exposure to apramycin; a control with exposure to apramycin; and apramycin plus either cold stress, heat stress, overcrowding, intermingling, poor sanitation, or intervention with oxytetracycline, to determine the effects of management and environmental conditions on antibiotic resistance among indigenous Escherichia coli. Pigs exposed to apramycin sulfate received that antibiotic in the feed at a concentration of 150 g/ton for 14 days. Environmental treatments were applied 5 days following initial antibiotic administration and maintained throughout the study. Fecal samples were obtained on day 0 (prior to antibiotic treatment) and on days 2, 7, 14, 28, 64, 148, and 149. E. coli were isolated and tested for resistance to apramycin using a minimum inhibitory concentration (MIC) broth microdilution method. Macrorestriction profiling, arbitrarily primed PCR, PCR targeting a gene coding for apramycin resistance, and DNA hybridization were used to characterize genetic elements of resistance. Increased (P<0.0001) resistance to apramycin was noted in E. coli from all treatment groups administered apramycin. MICs of isolates from control pigs receiving apramycin returned to pretreatment levels following removal of the antibiotic, whereas isolates from cold stress, overcrowding, and oxytetracycline groups expressed greater (P<0.05) MICs through day 64, before returning to pretreatment levels. Genetic analysis indicated that all resistant isolates carried the aac(3)IV gene sequence and this sequence was found in a variety of E. coli isotypes. Our data indicate that E. coli resistance to apramycin is increased upon exposure to various stressors.
断奶仔猪被分为八个处理组，包括一个未接触阿普拉霉素的对照组；一个接触阿普拉霉素的对照组；以及阿普拉霉素分别与冷应激、热应激、过度拥挤、混群、卫生条件差或土霉素干预相结合的处理组，以确定管理和环境条件对本地大肠杆菌抗生素耐药性的影响。接触硫酸阿普拉霉素的仔猪在饲料中以150克/吨的浓度接受该抗生素，持续14天。在首次给予抗生素5天后施加环境处理，并在整个研究过程中维持。在第0天（抗生素处理前）以及第2、7、14、28、64、148和149天采集粪便样本。分离大肠杆菌，并使用最低抑菌浓度（MIC）肉汤微量稀释法检测其对阿普拉霉素的耐药性。采用宏观限制性酶切图谱分析、随机引物PCR、靶向编码阿普拉霉素耐药性基因的PCR以及DNA杂交来表征耐药性的遗传元件。在所有给予阿普拉霉素的处理组的大肠杆菌中均观察到对阿普拉霉素的耐药性增加（P<0.0001）。接受阿普拉霉素的对照猪分离株的MIC在去除抗生素后恢复到预处理水平，而冷应激、过度拥挤和土霉素组的分离株在第64天前表现出更高（P<0.05）的MIC，之后才恢复到预处理水平。遗传分析表明，所有耐药分离株均携带aac(3)IV基因序列，并且该序列存在于多种大肠杆菌血清型中。我们的数据表明，大肠杆菌在接触各种应激源后对阿普拉霉素的耐药性会增加。
