An Investigation Of The Effective Content And Bactericidal Efficacy In Common Fishery Drugs And The Antibiotics Resistance Of Common Aquaculture Pathogens

Nowadays, medical treatment has proved to be one of the most important approachesin prevention and control of aquaculture diseases. However, the fishery drugs’ markettoday is full of drugs with greatly varied content and quality, mainly due to a lack ofmarket supervision, thus make it harder for the fish men to determine the correct drug dose.Long-term drug abuse has on one hand increased pathogens’ resistance to chemicals, andon the other hand, threatened the safety of the environment as well as the quality of aquaticproducts. In this study, we examined the qualified rate and bactericidal efficacy of thecommon fishery drugs. Besides, the author searched32kinds of pathogenic bacteria fortolerant genes that might be carried. To know the effective contents,34kinds of halogendisinfectants,8kinds of quinolones and5kinds of fluorfenicol drugs were detected byIodimetry, HPLC and UPLC-ESI-MS/MS, respectively. To know the bactericidal efficacy,the minimum inhibitory concentration (MIC) and minimum bactericidal concentration(MBC) of11kinds of disinfectants and13kinds of antibiotics were studied on Aeromonashydrophila and Vibrio alginolyticus. To investigate the drug resistance of pathogenicbacteria in aquaculture,32strains of pathogenic were detected for14kinds of resistancegenes. The results were as follows:(1) Effective content detection: Among the34kinds of disinfectants detected, therewere6whose measured content reached labeled standard, which accounted for19.35%.The number of the measured content between80%and100%of labeled standard was10,accounting for29.41%. The number of the measured content between50%and80%oflabeled standard was11, accounting for32.35%.4kinds of the measured content ofresidual were less than50%that of labeled, accounting for11.76%. Bactericidal efficacydetection: Among the10kinds of quinolones, only4kinds remained coincident with thecontent labeled on package, with the lowest measured content of quinolones to be only59.2%of labeled; among the5kinds of florfenicol drugs,3kinds reached the labeledstandard basically, while the remained two kinds reach only about25%of anticipatedpackage content. Conclusions: Fishery drugs sold on the market had the phenomenon that actual contents did not match the contents labeled on the package. The less effectivecontent of disinfectants is particularly prominent.(2) The MBC/MIC value of different fishery drugs against tested bacterium wasbetween1and2. The MIC and MBC of halogen disinfectants to Aeromonas hydrophilaand Vibrio alginolyticus were0.11~5.29mg/L and1.06~40.3mg/L respectively; MICand MBC of quinolones and florfenicol drugs to Vibrio alginolyticus were2.28～18.94mg/L and0.022～4.48mg/L respectively. Conclusions: Among the testeddisinfectants, quinolones and florfenicol drugs exhibited excellent inhibitory andbactericidal efficacy. Quinolones and florfenicol drugs had a much better bactericidalefficacy on Aeromonas hydrophila than on Vibrio alginolyticus; soluble florfenicol tend tobe more effective than powder type.(3) The test for the possible resistant genes of32pathogenic bacterium strainswere done:(a) fluoroquinolone-resistant genes carried: Among the total32strains,PMQR gene were detected in12strains, accounting for37.5%, with the dominantresistant gene of qnrA (3strains), qnrD (5strains) and qnrS (1strains), which accounts for9.4%,15.6%, and3.1%of the total respectively; resistant gene qnrB, qnrC, and aac(6’)-Ⅰ b-Cr were not detected; fflux pump-related genes oqxA (3strains) accounted for9.4%; resistant gene qepA and mdfA were not detected; enzyme structure-related resistant genes gyrA (15strains) and parC (1strains) accounted for46.9%and3.125%of the total respectively. Conclusions: the results showed that mariculture pathogenic bacteria in Zhejiang region had presented resistance to drugs ongene level.(b) florfenico-resistant genes carried: Among the32pathogenic bacteriastrains, the dominant resistant genes were floR (4strains) and fexA (13strains), accounting for12.5%and40.6%of the total respectively. Resistant genes fexB andcfrR were not detected. Conclusions: the results showed that more than a half of the tested pathogenic bacterium had carried florfenicol-resistant genes.