Granados-Chinchilla Fabio, Alfaro Margarita, Chavarría Guadalupe, Rodríguez César
a Centro de Investigación en Nutrición Animal (CINA) , Universidad de Costa Rica, Ciudad Universitaria Rodrigo Facio , San José , Costa Rica.
Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2014;31(6):1017-25. doi: 10.1080/19440049.2014.907504. Epub 2014 Apr 29.
Diverse tetracyclines are used to prevent and control bacterial infections in livestock and farmed fish. These drugs are administered through the diet, but farmers seldom check whether feed contains antibiotic-resistant bacteria that may colonise their crops or transfer their resistance traits to species of veterinary relevance. To examine whether antibiotic dosage defines the abundance of antibiotic-resistant bacteria in animal feed, we determined the concentration of parental compounds and epimers of oxytetracycline (OTC), doxycycline, tetracycline and chlortetracycline, as well as the abundance and resistance level of OTC-resistant bacteria in samples of fish (n = 21), poultry (n = 21), swine (n = 21), and shrimp feed (n = 21) marketed in Costa Rica. Fish feed contained the highest amounts of tetracyclines (119-8365 mg kg(-1)) and the largest proportion of bacteria resistant to 10 μg ml(-1) (1.8-92.4%) or 100 μg ml(-1) of OTC (12.5-63.8%). Poultry (78-438 mg kg(-1)) and swine (41-1076 mg kg(-1)) feed had intermediate concentrations of tetracyclines and OTC-resistant bacteria (0.2-66% and 0.3-49%, respectively), whereas shrimp feed showed the lowest amounts of tetracyclines (21.5-50.3 mg kg(-1)), no OTC and no culturable OTC-resistant bacteria. In line with these results, the MIC50 of OTC for 150 isolates from fish and poultry feed was > 256 µg ml(-1), while that of 150 bacteria isolated from swine feed was 192 µg ml(-1). Phenotypic tests, fatty acid profiles and proteotypic analyses by matrix-assisted laser desorption/ionisation-time of flight mass-spectroscopy revealed that most OTC-resistant isolates were Gram-positive bacteria of low G+C% content from the genera Staphylococcus and Bacillus. Clear correlations between OTC dosage and feed colonisation with OTC-resistant bacteria were seen in medicated feed for fish (r = 0.179-0.651). Nonetheless, some unmedicated feed for fish, swine and poultry contained large populations of OTC-resistant bacteria, suggesting that raw materials and manufacturing processes may also influence carriage of OTC-resistant bacteria in animal feed.
多种四环素类药物被用于预防和控制家畜及养殖鱼类的细菌感染。这些药物通过饲料投喂，但养殖户很少检查饲料中是否含有可能定殖于其养殖对象或向具有兽医相关性的物种转移耐药性状的抗生素抗性细菌。为了研究抗生素剂量是否决定动物饲料中抗生素抗性细菌的丰度，我们测定了土霉素（OTC）、强力霉素、四环素和金霉素的母体化合物和差向异构体的浓度，以及在哥斯达黎加市场上销售的鱼类（n = 21）、家禽（n = 21）、猪（n = 21）和虾饲料（n = 21）样本中耐OTC细菌的丰度和抗性水平。鱼饲料中四环素含量最高（119 - 8365 mg kg⁻¹），对10 μg ml⁻¹（1.8 - 92.4%）或100 μg ml⁻¹ OTC耐药的细菌比例最大（12.5 - 63.8%）。家禽（78 - 438 mg kg⁻¹）和猪（41 - 1076 mg kg⁻¹）饲料中四环素和耐OTC细菌的浓度处于中等水平（分别为0.2 - 66%和0.3 - 49%），而虾饲料中四环素含量最低（21.5 - 50.3 mg kg⁻¹），不含OTC且无可培养的耐OTC细菌。与这些结果一致，从鱼和家禽饲料中分离出的150株菌株对OTC的MIC50 > 256 µg ml⁻¹，而从猪饲料中分离出的150株细菌的MIC50为192 µg ml⁻¹。表型测试、脂肪酸谱分析和基质辅助激光解吸/电离飞行时间质谱的蛋白型分析表明，大多数耐OTC菌株是葡萄球菌属和芽孢杆菌属中G + C%含量低的革兰氏阳性细菌。在鱼类药饵中，OTC剂量与耐OTC细菌在饲料中的定殖之间存在明显的相关性（r = 0.179 - 0.651）。尽管如此，一些鱼类、猪和家禽的非药饵中含有大量耐OTC细菌，这表明原材料和生产工艺也可能影响动物饲料中耐OTC细菌的携带情况。
