Bacterial resistance to oxytetracycline in Chilean salmon farming
Bacterial resistance to oxytetracycline in Chilean salmon farming
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DOI：
10.1016/s0044-8486(02)00124-2
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发表时间：
2002-09-23
期刊：
影响因子：
4.5
通讯作者：
Zemelman, R
中科院分区：
文献类型：
--
作者：
Miranda, CD;Zemelman, R
在智利，使用土霉素预防和控制鲑鱼养殖中的细菌病原体是经常的，但尚未进行研究，以评估其密集和长期使用的生态影响。在这项工作中，土霉素耐药细菌的频率从水，颗粒饲料和鱼种从四个智利淡水大西洋鲑鱼养殖场，以及选定的菌株的耐药性水平进行了调查。通过涂布平板法进行活菌计数，并在补充有所选抗生素的培养基中对耐药菌进行计数。使用琼脂平板稀释法测定在含有抗生素的培养基中分离的选定菌株的抗性水平。高比例的低水平和高水平的土霉素耐药菌（分别在含有30和100 μ g/ml的琼脂平板中选择），主要来自颗粒饲料和养鱼场的废水样品。在废水样品中发现的耐药菌比例最高，并且显著高于（P < 0.05，Tukey检验）来自其他研究样品的耐药菌。相反，进水样品表现出最低比例的耐药细菌。在含有30或100 μ g/ml土霉素的TSA上从鲑鱼养殖场和颗粒样品中随机选择103株代表土霉素耐药细菌群体的耐药革兰氏阴性分离株，并在不含土霉素的TSA平板上划线纯化。大量的非发酵菌（77.7%）被鉴定出来。其中以荧光假单胞菌（28.2%）、嗜麦芽窄食单胞菌（5.8%）、少动鞘氨醇单胞菌（5.8%）、鲁氏不动杆菌（4.8%）和恶臭假单胞菌（4.8%）最为常见。另外，还发现了大量的嗜水气单胞菌（9.7%）、洋葱伯克霍尔德菌（3.9%）、泡囊短单胞菌（3.9%）、约氏不动杆菌（2.9%）、泛菌属（2.9%）和莫拉氏菌属（2.9%）。在鲑鱼鱼种中，A. lwoffii和S.嗜麦芽窄食单胞菌在颗粒样品中占优势。所选菌株表现出高水平的土霉素耐药性，最低抑菌浓度（MIC）范围为64至2048 μ g/ml，而土霉素的MIC 90在1024至2048 μ g/ml之间变化。这项研究表明，在智利鲑鱼养殖场的微生物群落中存在一个重要的土霉素耐药菌群。因此，这些农场的环境可能作为携带hi遗传决定因子的细菌的储存库发挥重要作用。h级四环素耐药性，对从事鱼类养殖和加工的工人的公共卫生构成重大风险。(C)2002 Elsevier Science B. V.保留所有权利。
The use of oxytetracycline for preventing and controlling bacterial pathogens in salmon farming is frequent in Chile, yet no studies have been performed to evaluate the ecological impact of its intensive and prolonged use. In this work, the frequency of oxytetracycline-resistant bacteria from water, pelletized feed and fingerlings from four Chilean freshwater Atlantic salmon farms, as well as the level of resistance of selected strains was investigated. Viable bacterial counts were performed by a spread plate method and antibiotic-resistant bacteria were counted in culture media supplemented with the selected antibiotic. Resistance levels of selected strains isolated in media containing antibiotic were determined using an agar plate dilution method. High proportions of low- and high-level oxytetracycline-resistant bacteria (selected in agar plates containing 30 and 100 mug/ml, respectively), mainly from pelletized feed and effluent samples of the fish farms were found. The highest proportions of resistant bacteria were found in the effluent samples, and were significantly higher ( P < 0.05, Tukey's test) than those from the other samples studied. On the contrary, influent samples exhibited the lowest proportions of resistant bacteria. One hundred and three resistant Gram-negative isolates, which represented the oxytetracycline-resistant bacterial population, were randomly selected on TSA containing 30 or 100 mug/ml of oxytetracycline, from salmon farms and pellet samples, and streaked for purification on TSA plates without oxytetracycline. A large number of non-fermenting bacteria (77.7%) were identified. Among these, Pseudomonas fluorescens (28.2%), Stenotrophomonas maltophilia (5.8%), Sphingomonas paucimobilis (5.8%), Acinetobacter lwoffii (4.8%), and Pseudomonas putida (4.8%) were the most frequent. Also, an important number of strains of Aeromonas hydrophila (9.7%), Burkholderia cepacia (3.9%), Brevundimonas vesicularis (3.9%), Acinetobacter johnsonii (2.9%), Pantoea sp. (2.9%) and Moraxella sp. (2.9%) were found. P fluorescens and A. hydrophila predominated in salmon fingerlings, whereas A. lwoffii and S. maltophilia were predominant in pellet samples. Selected strains exhibited high levels of oxytetracycline resistance, with minimum inhibitory concentrations (MICs) ranging from 64 to 2048 mug/ml, whereas MIC90 of oxytetracycline varied between 1024 and 2048 mug/ml. This study shows the presence of an important population of oxytetracycline-resistant bacteria in the microflora of Chilean salmon farms. Therefore, die environment of these farms might play important roles as reservoirs of bacteria carrying genetic determinants for hi.-h-level tetracycline resistance, prompting an important risk to public health for workers involved in fish culturing and processing. (C) 2002 Elsevier Science B.V. All rights reserved.