Identification and drug sensitive test of the pathogen in Acinetobacter disease from hybrid crucian carp (Carassius auratus gibelio ♀ × Cyprinus carpio ♂).

Five bacteria were isolated from the visceral samples of moribund hybridized crucian carp(Carassius auratus gibelio♀×Cyprinus carpio♂).The ID% and T value of the strain YCS07-04 identified as Acinetobacter baumannii was 99.5% and 0.9 by API 20NE.The artificial infection with three different concentrations showed that the high dosage group with 5.0×106 cfu/ml performed high infectivity and caused 100% mortality by injecting in 14 days.Three fish was dead of the bacterium immersing while the healthy fish without clinic disorder was observed in the control group.The isolated bacterium grew well in Nutrient Agar,cloudy with pellicle in nutrient broth,and showed gray white non-hemolytic colonies in rabbit blood agar and colorless transparent colonies on MacConkey agars,but did not live on SS agars.Negative staining under electron microscope revealed that the isolated bacterium was short straight rods with rounded ends in shape and(1.0～1.5)μm×(1.5～2.5)μm in size,becoming spherical in the stationary phase of growth,and to be big irregular filament when gathering.It has rough surface without flagellum,gemma and capsule.The isolated bacterium strain YCS07-04 was sensitive to streptomycin,tobramycin,gentamicin,levofloxacin,lomefloxacin and sulfamethoxazole compounds,and intermediate to tetracycline,while resistant to carbenicillin,ceftazidime,aztreonam and etc.