ASHOK, VASILI (Major)ESWAR PRASAD, PKrishnaiah, NSAMPATH KUMAR, B2017-06-102017-06-102012-08http://krishikosh.egranth.ac.in/handle/1/5810019318THESESABSTRACT : Antibiotics are the drugs used to kill or inhibit the growth of bacteria. Presence of antibiotic residues in milk has significant public health importance as they have adverse side effects on the health. The present study was undertaken to produce polyclonal antibodies against the most commonly used antibiotics in large animal practice so that a diagnostic test can be developed to screen milk samples for the presence of antibiotic residues. Ampicillin, ceftiofur, enrofloxacin and gentamycin were conjugated with carrier protein BSA by carbodiimide method in which EDC was used as a crosslinking agent. Successful conjugation was confirmed by SDS PAGE in which antibiotic conjugates revealed high molecular weight protein bands of 90kDa, 85kDa, 78kDa, 74kDa for gentamycin, ampicillin, ceftiofur and enrofloxacin respectively in contrast to 68kDa band of BSA. Sprague Dawley rats aged 7-8 weeks were immunized with the antibiotic-BSA conjugates by subcutaneous route according to the standard immunization schedule. A total of four blood samplings were done from each group (3 animals) as follows: first three samples serially at 15 days time interval after 1st immunization plus 1st booster, 2nd booster, 3rd booster and the 4th sampling one and half month after the third booster. The mean total protein content in the antisera of ampicillin, ceftiofur, enrofloxacin and gentamycin groups were 12±1.15 g/dL, 30±1.20 g/dL, 24±1.73 g/dL and 8.25±0.20 g/dL respectively and in the control group serum it was 6.66±0.01 g/dL. The mean albumin concentrations were 3.44±0.020 g/dL, 3.36±0.173 g/dL, 3.21±0.003 g/dL & 2.93±0.014 g/dL for ceftiofur, ampicillin, enrofloxacin and gentamycin groups respectively compared to 3.36±0.173 g/dL in the control group. The mean globulin content in the antisera of ampicillin, ceftiofur, enrofloxacin and gentamycin groups were 8.64±0.10 g/dL, 26.56±1.18 g/dL, 20.79±0.08 g/dL and 5.32±0.05 g/dL respectively and it was 3.30±0.04 g/dL in the control group. A/G ratios were less than the normal value (>1) in antisera of ampicillin, ceftiofur, enrofloxacin and gentamycin groups. Indirect ELISA was standardized with antibiotic-casein conjugate as coating antigen to detect antibody titres. The optimum antigen concentration was chosen as 20ng/ml (which was in the range of Maximum residue limits) and optimum antiserum dilution was chosen as 1/100 by checker board titration. The antibody titres in the test samples of 4 immunization cycles for each antibiotic were determined by indirect ELISA at various serum dilutions ranging from 1/100 to 1/6400. Cut off value of 0.3 was calculated from PNT base line constructed with M+3SD values of control serum samples. All the four antibiotic-BSA conjugates elicited positive immune response in rats. The immune response in BSA-ampicillin conjugate immunized rats was maximum with the highest antibody titre of 2.577 (OD450) followed by BSA-ceftiofur conjugate immunized rats, BSA-enrofloxacin conjugate immunized rats and BSA-gentamycin immunized rats with OD450 values of 2.072, 1.723, and 0.928 respectively at the antiserum dilution of 1/00. These polyclonal antibodies are the efficient tools for developing immunoassays to detect specific antibiotic residues in biological fluids like milk and urineenThesis