Twenty-six strains of Aeromonas hydrophila isolated in cultured fish and soft-shelled turtles were collected from various areas of China. Their susceptibilities to 21 antibacterial agents were studied by disc diffusion method. It was showed that all strains tcsted were resistant to pcnieillin and cephalosporins. Most of the strains were sensitive to norfloxacin, chloramphenicol and furazolidone, but up to 73.1%, 70. 1% and 50. 0% of strains tested showed resistance to sulfonamides, aminogylcosides and tetracyclines respectively. Meanwhile, their susceptibilities were examined by micro-dilution procedure against 8 commonly used antibacterials including ampicillin, furazolidone, teltracycline, oxytetracyeline ,steptomycin, chloramphenicol, sulfonamides and ciprofloxacin. Only two of 26 strains of A. hydrophila were sensitive to all drugs tested except ampicillin. The remaining 24 strains were resistant to various combinations of 8 drugs. Majority of the strains carried a marker of resistance to 2～3 drugs and highly sensitive to ciprofloxacin and chloramphenicol.rn The results indicated that A. hydrophila was highly resistant to most of common antibioties in China and more new antibacterials should be introduced into aquaculture to control ever-increasing fish diseases. The criterion for drug resistant bacteria was also discussed in this paper.%采用琼脂扩散法和稀释法研究26株嗜水气单胞菌对21种抗菌药物的敏感性，分析了其耐药状况。结果表明：从不同地区分离收集到的26株嗜水气单胞菌(Aeromonas hydrophila)对青霉素类和头孢菌素类药物全部具耐药性，对万古霉素多数不敏感。21种药物中最敏感的是氟哌酸、氯霉素、呋喃唑酮，总体耐药率分别为7.7％、7.7％和11.5％。氨基糖甙类药物和四环素类药物的耐药频率介于其间。对磺胺药的耐药菌比例也很高，高达73.1％的A.hydrophila对磺胺及复方磺胺其有耐药性，但耐磺胺比耐复方磺胺的现象更为普遍。对3种常用药物具有耐药性的菌株比例最高。同时对鱼类病原菌耐药性的判定标准以及两种试验方法在鱼类病原菌耐药性研究中的适用性问题进行了讨论。
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