Isolation and identification of pathogenic bacteria associated with"rot disease"of hybrid yellow catfish(Pelteobagrus fulvidraco,♀×P.vachell,♂)
In order to recognize the pathogenic bacterial characteristics of hybrid yellow catfish(Pelteobagrus ful-vidraco,♀×P.vachell,♂)"Huangyou No.1"with"rot disease",a dominant strain from the skin of diseased cat-fish was isolated and cultured,and the pathogenicity and the species pathogen were determined in healthy"Hwan-gyou No.1"with body weight of 45.3-55.2 g and glossy yellow catfish(P.nitidus)with body weight of 31.9-41.7 g)by artificial infection test,and confirm by comprehensive morphological observation,physiological and bio-chemical identification,as well as16SrRNA gene sequence analysis.The virulence gene and drug sensitivity of the strain were detected by PCR method,and antibiotic drug sensitivity tests.The results showed that the strain was a Gram-negative bacterium,with 15 days LD50 of 2.11×108 CFU/mL for the hybrid yellow catfish and 4.27×108 CFU/mL for P.nitidus,by artificial regression infection.The physiological and biochemical identifica-tion,and the sequencing analysis confirmed that the strain was Pseudomonas fluorescens.Virulence gene testing showed that it carried virulence genes including fur,hly,hem0,fha,pspb and tfeR.The strain was a multi-drug re-sistant strain,highly sensitive to 4 antibiotics including doxycycline,gentamicin,benznidazole and tetracycline,and resistant to 14 antibiotics including penicillin in drug sensitivity tests.The P.fluorescens is first reported a poten-tial pathogen causing"rotten disease"in hybrid yellow catfish,and that also cause similar disease in P.nitidus.The findings provide scientific basis for the prevention and treatment of rotten disease in yellow catfish.
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