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. 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.

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. 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.