ABSTRACT Intensive livestock production uses antibiotics to treat and prevent infectious diseases. Antibiotics are expelled unaltered in animal manure, which is often used as a fertilizer. This practice spreads antibiotic residues and antibiotic-resistant bacteria and their genes into the soil. These resistance determinants affect soil microbial communities, raising concerns about the potential environmental and public health risks. This study aims to characterize soil contaminated with antibiotic resistant bacteria and the putative role played by manure as a vector for these resistance determinants. Six poultry and dairy cattle farms in the central region of Portugal were sampled. Ampicillin-resistant Enterobacteriaceae isolates from manure and manured-soil samples were tested for their resistance profile to 13 antibiotics and the presence of tetracycline and sulfonamide resistance genes. High multidrug resistance rates (>70%) were observed in both manure and soil samples. This resistance was higher in the poultry samples; manured-soil isolates were more resistant to cefoxitin (91.7%), sulfamethoxazole/trimethoprim (79.2%), chloramphenicol (79.2%), and to a lesser extent tetracycline (12.5%). Manure isolates have high resistance frequency to tetracycline (73.9%), amoxicillin with clavulanic acid (66.0%), chloramphenicol (65.3%), and sulfamethoxazole with trimethoprim (36.5%). Manure isolates revealed high frequency of tet(A), sul1, and sul3 genes. The multiple antibiotic resistance index reveals a putative risk of soil contamination due to antibiotic exposure. The results obtained are important for soil management regarding resistance determinants spread through agricultural practices. To our knowledge, this is the first study of tetracycline and sulfonamide resistance in Portuguese manure and soil.

中文翻译：

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葡萄牙农业粪便和土壤中肠杆菌科细菌耐药性的表征

摘要 集约化畜牧生产使用抗生素来治疗和预防传染病。抗生素在动物粪便中原封不动地排出，动物粪便通常用作肥料。这种做法会将抗生素残留物和抗生素抗性细菌及其基因传播到土壤中。这些耐药性决定因素会影响土壤微生物群落，引起人们对潜在环境和公共健康风险的担忧。本研究旨在表征被抗生素抗性细菌污染的土壤，以及粪便作为这些抗性决定因素的载体所发挥的假定作用。对葡萄牙中部地区的六个家禽和奶牛养殖场进行了抽样。对来自粪便和粪肥土壤样品的耐氨苄青霉素肠杆菌科细菌进行了测试，以确定它们对 13 种抗生素的耐药性以及四环素和磺胺类耐药基因的存在。在粪便和土壤样品中均观察到高多药耐药率 (>70%)。在家禽样本中这种抵抗力更高；粪便分离株对头孢西丁 (91.7%)、磺胺甲恶唑/甲氧苄啶 (79.2%)、氯霉素 (79.2%) 和四环素 (12.5%) 的耐药性更强。粪便分离株对四环素 (73.9%)、阿莫西林和克拉维酸 (66.0%)、氯霉素 (65.3%) 和磺胺甲恶唑和甲氧苄啶 (36.5%) 的耐药率很高。粪便分离物显示出高频率的 tet(A)、sul1 和 sul3 基因。多重抗生素抗性指数揭示了由于接触抗生素而导致土壤污染的推定风险。获得的结果对于通过农业实践传播的抗性决定因素的土壤管理很重要。据我们所知，这是对葡萄牙粪便和土壤中四环素和磺胺耐药性的首次研究。