The Effect Of Commonly Used Antibiotics On Immune Functions Of Mub Crab

In this paper,17antibiotics and antibacterial medicines, including quinolones, aminoglycosides, tetracyclines,macrolides, etc., which commonly used in aquaculture disease prevention and control, were used for evaluationthe potential effects on the immune functions of mud crab. The phenol oxidase (PO) was used as the index byantibiotics and antibacterial medicines with different drugs at series of concentrations in vitro. On thepreliminary results by PO,3quinolones were selected to study the effects of these antibiotics on the immuneresponses in mud crab, by injected into mud crab. And phenol oxidase (PO), superoxide dismutase (SOD),peroxidase (POD), alkaline phosphatase(ALP), lysozyme(LSZ), glutamic-oxalacetic transaminease(AST),glutamic-pyruvic transaminase(ALT) were tested by the commercial kits.The effects of of PO by17common used antibiotics on the immune functions of mud crab. The resultsshowed that all the antibiotics gave apparent inhibition on PO at a concentration of500μg.mL-1. The inhibitionrate (HI) of gentamicin, kanamycin, amikliin etc was10%～25%at the usage dose of5～10μg.mL-1.Norfloxacin, ciprofloxacin, ofloxacin and other three antibiotics showed weak inhibition, with HI of5%～10%at usage dose, while HI of erythromycin, enrofloxacin and other two antibiotics was below5%; avilamycin andflorfenicol showed enhancing effects on PO of mud crab.Norfloxacin, ofloxacin and enorfloxacin, the most common used quinolones in aquaculture, were evaluatedfor the effects on hemolymph enzymes of mud crab, Scylla serrata. All three quinolones showed obviousinhibition on hemolymph phenoloxidase (PO) in vitro when concentration of quinolones was higher than100μg.mL-1, with correlation between PO inhibition and quinolones concentration. The relative inhibition ofofloxacin, norfloxacin and enorfloxacin on PO was80.21%、59.87%and18.79%respectively at the concentrationof500μg.mL-1. Quinolones showed no inhibition on PO at5μg.mL-1, and enorfloxacin even showedenhancement on PO activity. The hemolymph was collected at regular time for detection of phenoloxidase,peroxidase(POD), superoxide dismutase(SOD), alkaline phosphatase(ALP), lysozyme(LSZ),glutamic-oxaloacetic transaminase(GOT) and glutamic-pyruvic transaminase(GPT) after mud crabs were injectedintramuscularly with quinolones at concentration of5μg.kg-1. The results showed that activity of PO, POD andSOD increased by40%,24%and14%respectively at6-12h after injection, and decreased to the normal level asthe control group at96h. The activity of ALP and LSZ was increased by26%and47%at48h and24h, comparedwith the control group, and decreased to normal level at96h. No significant difference was observed in GOT/GPTafter quinolones injection, and quinolones injection group showed lower transaminase activity at96h. Theseresults indicated that quinolones did not result in inhibition on hemolymph immunol enzyme and damage onvisceral organs. Moreover, quinolones showed immunol enhancement on mud crab at low concentration.