Study On The Phenotype And Virulence Of Aeromonas Hydrophila ZHYYZ-1and The Screening Of Antibacterial Chinese Herb Formula

The pathogen Aeromonas hydrophilia ZHYYZ-1was isolated from the moribundChinese Softshell Turtle (Trionyx sinensis) with typical white abdominal shell disease. Thecharacteristics of ZHYYZ-1were that:(1) elliptic and rod shaped bacterium withperiplasmic flagella, which colony is uplift in centre. In the blood agar plate, had βtypehemolysis.(2) The suitable bread worm is25.0～35.0℃, the suitable pH for propagationis6.0～8.0, the suitable mass concentration of NaCl for breeding is0.5%～1.5%.(3) Itwas sensitive with Aminoglycoside antibiotics (Amikacin, Gentamicin, Tobramycin),Quinolones (Norfloxacin, Levofloxacin) and sulfonamides (Compound sulfamethoxazole),and was resistant to Tetracycline antibiotics (doxycycline, tetracycline), Streptomycin andNeomycin.(4) It had virulence gene including that aerolysin (AerA), hemolysin (AHH),Adhesin (Aha) and outer membrane protein (OMP).To study the pathogenicity of Aeromonas hydrophilia ZHYYZ-1, Chinese SoftshellTurtle juvenile which were born for20days was challenged with ZHYYZ-1byintraperitoneal injection. Post infection the Chinese Softshell Turtle juvenile were put inthe standing water without feeding. The results showed that:(1) the clinical symptoms ofChinese Softshell Turtle post infection was abnormal evacuation.(2) Most of themappeared the symptoms of disease in2hours, and died in48hours.(3) Among them, thegroup which was injected ZHYYZ-1with1.0×10~5CFU/mL showed no clinical symptoms,and no died. The group which was injected ZHYYZ-1with1.0×10~6CFU/mL showedapparent clinical symptoms, still no died. However, the group which was injectedZHYYZ-1with1.0×10~7CFU/mL showed evident lethal effect, and the mortality up to80%.(4) The variation characteristics of ZHYYZ-1in the body of moribund Chinese SoftshellTurtle juvenile indicated that the lowest limit of ZHYYZ-1were3.3×10~6CFU/g. The saferange concentration of ZHYYZ-1in juvenile was (1.2～8.8)×10~3CFU/g.Using Agar dilution method，antibacterial effect in vitro of ten common Chinese herbswere observed. And screened out the optimum formulas which have the effective ofanti-Aeromonas hydrophila ZHYYZ-1. The results showed that (1) Gallnut、Scutellariabaicalensis Georgi、 Honeysuckle、 Dandelion have better bacteriostatic efficacy onZHYYZ-1, and the minimum inhibition concentration (MIC) were:0.78mg/mL forGallnut,3.12mg/mL for Scutellaria baicalensis Georgi,6.25mg/mL for Honeysuckle, 12.50mg/mL for Dandelion, as bacterial suspension concentration is1.0×10~7CFU/mL.（2）Dandelion-Galla chinensis, Honeysuckle-Dandelion had antagonistic effect inantibacterial； Dandelion-Scutellaria baicalensis Georgi, Scutellaria baicalensisGeorgi-Honeysuckle had synergistic effect, and when the mass concentration ofconscutellaria baicalensis Georgi was0.67times of Gallnut’s the mixture of themappeared effect synergistic effect in antibacterial. The MICs for inhibiting the bacterialsuspension (1.0×10~7CFU/mL) were that:2.92mg/mL for A, and2.19mg/mL for B.