Studies On The Main Pathogenic Bacteria From Cultivated Anguilla Marmorata And A. Bicotor Pacifica

In this paper, the main pathogenic bacteria isolated from diseased cultivated Anguillamarmorata and A. bicolor pacifica were studied. By using the serum kit made by our laboratoryto30strains of pathogenic bacteria, the strains isolated from gills and liver of diseased eels indifferent seasons were tested. The undetected strains were identified based on the morphologicalcharacters of bacteria, traditional physiological and biochemical identification, and the BiologAutomic Identification System. The new isolated strains were used for artificial infection test andthe inhibitory effects of10kinds of Chinese herbs in vitro, including Rhus Chinensis Mill(RCM),Rheum Palmatum Linn(RPL), Punica Granatum Linn(PGL) etc. The main results are asfollowing:1. After primary test by the serum kit, the undetected strains were further identified bybiochemical identification. Results showed that15pathogens（B06、B08、B09、B10、B11、B16、B18、B19、B20、B21、B26、B27、B30、B32、B43）could be detected by the serumkit in120diseased Anguilla marmorata.29pathogens were isolated and purified from other52diseased Anguilla marmorata could not be detected by serum kit.9pathogens were accuratelyidentified as Aeromonas hydrophila (1), Acinetobacter baumannii (1), Aeromonas hydrophilaDNA1type (1), Citrobacter freundii (1), Edwardsiella tarda (1), Aeromonas bestiarum (2),Pseudomonas mendocina (2). Meanwhile,15pathogens（B04、B05、B06、B08、B10、B11、B12、B14、B18、B19、B21、B26、B27、B31、B32）could be detected by the serum kit in86diseased A. bicolor pacifica.12pathogens were isolated and purified from other34diseased A.bicolor pacifica could not be detected by the serum kit.4pathogens were accurately identified asAeromonas hydrophila, Edwardsiella tarda1group, Plesimonas shigelloides, Aeromonas caviae.2. Based on the artificial infection test, strains with strong toxicity were selected to test itsmedian lethal concentration (LD50) in eels. The results indicated that5strains (Aeromonashydrophila, Aeromonas hydrophila DNA1type, Aeromonas bestiarum, Pseudomonas mendocina,Citrobacter freundii) had obvious pathogenicity to healthy Anguilla marmorata, and the LD50respectively were3.16×106CFU/mL、2.15×106CFU/mL、2.15×106CFU/mL、4.64×106CFU/mLand3.2×107CFU/mL.4strains (Aeromonas hydrophila, Edwardsiella tarda1group，Plesimonasshigelloides, Aeromonas caviae) had obvious pathogenicity to healthy A. bicolor pacifica, andthe LD50respectively were1.47×107CFU/mL、1.78×106CFU/mL、3.52×107CFU/mL and3.98×106CFU/mL. 3. Combined the results of the serum kit and artificial infection test, the species ofpathogens and regularty of epidemic of Anguilla marmorata and A. bicolor pacifica wereinvesgated in the breeding process regarding eel sizes and seasons. Results showed that161fishof Anguilla marmorata were tested and20strains were detected. The strain B26could bedetected in five sizes of Anguilla marmorata, and the6strains including B19、B21could bedetected in three reasons. Also,112fish of A. bicolor pacifica were tested and19strains weredetected. The strain B26could be detected in five sizes of A. bicolor pacifica, and the5strainsincluding B18、B32were also detected in three reasons.4.10kinds of traditional Chinese medicines, such as Rhus Chinensis Mill(RCM), RheumPalmatum Linn(RPL), Punica Granatum Linn(PGL),ect.were selected to test the MIC (minimuminhibitory concentration) and MBC (minimum bactericidal concentration) against mainpathogens isolated from eels either by single herb, or the compound of two herbs or three herbsin vitro. The result showed that: all above10kinds of traditional Chinese medicines had betterantibacterial effects against the8sorts of main pathogenic bacteria and the average MIC werebetween1.6875mg/mL and13.14mg/mL. five single herbs with better effects were choosed todesign10double-compound prescriptions, which were used to examine the bacteriostatic effectsin vitro by ultrafine powder agar dilution method. Results showed that the inhibitory effects ofdouble-compound prescription were enhanced and all presented synergistic effect. According tothe above results, four single herbs were used to compose triple-compound prescriptions. Resultsindicated that the triple-compound prescriptions all presented synergistic effect against eightpathogenic bacteria, which can greatly reduce the dose of herbs.The results in this study indicated that15strains of pathogenic bacteria from diseased eels(Anguilla marmorata) were dectected by the serum kit and five strains were newly isolated.15strains of pathogenic bacteria from diseased eels (A. bicolor pacifica) were dectected by theserum kit and four strains were newly isolated. The artificial infection test proved the strainsvirulence had significant difference. The major pathogens of Anguilla marmorata and A. bicolorpacifica had specificity among different species sizes and seasons. The compounds of Chineseherbals could enhance the efficacy of inhibition on the pathogenic bacteria. The results from thisstudy had important application and reference values for diagnosis and treatment of bacterialpathogens of cultivated Anguilla marmorata and A. bicolor pacifica.