Study On The Residue Elimination Of Bacitracin Methylene Disalicylate Soluble Powder In Rabbits

Bacitracin methylene disalicylate is a methylene salicylate of bacitracin.It has good biological activity against gram-positive bacteria and clostridium perfringens.BMD indications approved include to improved weight gain and feed utilization,increased egg production in laying hens,prevention of necrotizing enteritis in chickens,treatment of contagious enteritis in turkeys,prevention of ulcerative enteritis in quail and prevention of diarrhea in pigs.BMD is also recommended in the European Union for the treatment of rabbit necrotizing enteritis caused by clostridium perfringens.The purpose of this study was to establish a HPLC-MS/MS method for detecting the residual markers of bacitracin in eible tissues(muscle,fat,kidney and liver)of rabbit,and to study the residual elimination of BMD in rabbit tissues,so as to provide evidence for the establishment of withdrawal time for BMD in rabbits.1.The HPLC-MS/MS method for detection of bacitracin A and bacitracin B residues in rabbit tissuesThe rabbit tissue samples(muscle,fat,liver and kidney)were precipitated with acetonitrile trichloroacetate,extracted with 0.5%trifluoroacetic acid water,hexane removed fat,and purified with SPE.Gradient elution was conducted with 0.1%formic acid water and acetonitrile(0-0.5 min 15%acetonitrile,7.5-8.0 min 85%acetonitrile,8.1-10.0 min 15%acetonitrile)as the gradient elution.Electrospray ion source(ESI),positive ion mode and MRM mode were used in mass spectrometry.The results showed that the linear relationship between the concentration and response value of bacitracin was good in the concentration range of 50?1000 ng/g(calculated by bacitracin),and the correlation coefficient was greater than 0.99.The detection limit of the method was 30 ng/g,and the quantitative limit was 50 ng/g.The average recovery rate of bacitracin was 74.7%?83.8%.The method developed in this study can meet the requirements of detection of residual bacitracin in rabbit tissue.2.Study on the residual elimination of bacitracin methylene disalicylate Soluble Powder in rabbitsTwenty healthy rabbits were given by 6 mg/kg·bw/d(bacitracin)dose through drinking water for 10 consecutive days,and four rabbits were slaughtered at 12 h,1 d,2 d,3 d and 5 d respectively after drug withdrawal.Edible tissues such as muscle,fat,liver and kidney were collected for detection of bacitracin residue markers.The results showed that no residual markers of BMD--bacitracin A and bacitracin B--were detected at the above time points.In view of this,the withdrawal time of bacitracin methylene disalicylate soluble powder used in the prevention and treatment of necrotizing enteritis in rabbits can be set as 0 days.The results of residue elimination studies also confirmed that bacitracin methylene disalicylate soluble powder was almost not absorbed by rabbits after oral administration.