Identification and antibiotic sensitivity of pathogenic bacterium Pseudomonas aeruginosa isolated from diseased grass carp
CUI Lai-bin,YE Xing,DENG Guo-cheng,JIANG Xiao-yan,TIAN Yuan-yuan,BAI Jun-jie,LI Jian-ping
1.Pearl River Fisheries Research Institute,Chinese Academy of Fishery Sciences;Key Laboratory of Tropical ＆ Subtropical Fish Breeding ＆ Cultivation,Guangzhou 510380,China;2.College of Fisheries and Aquatic Life Science,Shanghai Ocean University,Shanghai 201306,China;3.The Aquaculture Technique Promotion Station of Guangdong Province,Guangzhou 510380,China
Abstract: A pathogenic bacterium was isolated from skin of diseased grass carp Ctenophyaryngodon idellus showing pathological signs similar to those observed on fish suffered from ＂red skin disease＂,including significant external lesions of inflammation,and haemorrhagic and exfoliation scales as well as rot or decay fins.Artificial infection experiment by intraperitoneal injection of the bacterium（0.2 mL of bacterium,3×109 cfu/mL） or immersion of the injured fish with the bacterium（3×108cfu/mL） showed that 100% mortality of the tested grass carp,with similar symptoms found in those natural infection and that the isolated bacteria possessed strong virulence.The bacterial morphology observation,physiology and biochemistry assays suggested that the isolated bacterium was found to be Pseudomonas aeruginosa.The three genes,16S rRNA,rpoB（RNA polymerase beta subunit） and gyrB（DNA gyrase beta subunit） were cloned,sequenced and analyzed in the bacterium by a molecular method.BLAST showed that all the three genes shared high similarities with their counterparts of P.aeruginosa found in GenBank.Similarities of the genes of the isolated bacterium with those in GenBank were found to be above 99% for 16S rRNA,98% for rpoB and 93% for gyrB genes.Both physiological and biochemical assays and molecular identification suggested that the bacterium isolated was a strain of P.aeruginosa.The drug sensitivity test show that the isolated bacterium was highly sensitive to eleven kinds of antibiotics such as Amikacin,Rocephin,Fupaisuan and Tobramycin,intermediately sensitive to Streptomycin and Gentamicin,and resistant to sixteen kinds of antibiotics including Roxithromycin,Erythromycin,Tetracycline,Oxazocilline,Neomycin and Cephalexin.
2010, Vol. 25 
