The Screening Of Controlling Medicines On Streptococcus Agalactiate From Tilapia

Streptococcus agalactiate?S.agalactiate?,a kind of zoonotic pathogen,poses a serious threat to aquaculture,animal production and human health.In order to find out new safe drugs which have antimicrobial effect against S.agalactiate,the research is aimed to investigate the antimicrobial activity of 36 natural compoundsand 14antibiotics against 3 pathogenic S.agalactiate strains 333,319,PBSA0903 isolated from diseased tilapia by disc agar diffusion and broth micro-dilution method to screen the best antibacterial agents against S.agalactiate.The result showed that all tested stains were extremely sensitive to sanguinarine,chelerythrine,magnolol,honokiol and rhein,and sensitive to enrofloxacin,florfenicol,cefotaxime,cefradine,doxycycline,sarafloxacin.The minimum inhibitory concentration?MIC?of sanguinarine against 3 S.agalactiae strains of were 8,8,16?g/mL,the MIC of ssarafloxacin against 3 S.agalactiae strains of were 1,1,0.5?g/mL,both of the drugs have effective antimicrobial activities.Further growth curve and biofilm test implied different of concentration sanguinarine had antimicrobial effect on the growth and the biofilm formation of S.agalactiate,the biofilm formation of S.agalactiate was less than 2.76%once sanguinarine concentration reached 16?g/ml.Which showed sanguinarine may bring antibacterial effect to the strains through acting on biofilm.Furthermore,a HPLC methord was developed for the determination of sarafloxacin in tilapia plasma and tissues.sarafloxacin in the samples was extracted by the acetonitrile,water,hydrochloric acid with fixed proportion.Mobile phase consisted of triethylamine,acetonitrile and water.The lower limit of quantification of sarafloxacin in the plasma,muscle,liver,kidney,brain was 0.03?g/mL or?g/g,the levels of absolute recoveries of sarafloxacin were above 70%.The results indicated that the detection method of sarafloxacin was rapid,simple and sensitive,which could satisfy the following study.a method to detect sarafloxacin in plasma and tissues of tilapia using phase high performance liquid chromatography?HPLC?.Plasma,muscle,liver,kidney and brain were sampled at different intervals after oral administration of sarafloxacin at single dose of 20mg/kg under 26±2?.The pharmacokinetic parameters were analyzed by non-compartmental method based on statistical moment theory.The minimum inhibitory concentrations?MIC?and postantibiotic effect?PAE?of sarafloxacin on the pathogenic S.agalactiate were detected.The pharmacokinetics/pharmacodynamics?PK/PD? parameters were calculated.The peak drug concentrations(C_max) and the peak drug concentration(T_max) in plasma were estimated to be 8.36?g/mL and 12 h,the AUC and AUC_0-24-24 were 193.10,127.23 mg/L·h.The MIC of sarafloxacin on the pathogenic S.agalactiate 333,319 and PBSA0903 from Tilipia were1,1,0.5?g/ml,the C_max/MIC and AUC_0-24/MIC of the strains on tilapia were 8.36,8.36,16.72 and 127.14,127.14,254.28.The drug concentrations in plasma maintained above the effective concentrations?MIC? beyond 40 h,the drug level of muscle was below 0.03?g/g?MRL? after administration of 72 h,which indicated sarafloxacin was effective against pathogens and can be rapidly eliminated.The treatment test on tilapia infected S.agalactiate was carried out with sanguinarine and sarafloxacin.The results showed 6h after intraperitoneal injection of S.agalactiate into tilapia with 0.2mL/tail,with the dosage of 20 mg/kg by oral administration of sanguinarine can effectively against the infections combat bacterial diseases caused by S.agalactiate at a 60%survival rate,and the dosage of 20 mg/kg by oral administration of sarafloxacin can effectively combat bacterial diseases caused by S.agalactiate at a 50%survival rate.That is,two drugs can effectively prevent bacterial diseases caused by S.agalactiate.