Immunobiosensor - an alternative to enzyme immunoassay screening for residues of two sulfonamides in pigs

A rapid immunoassay using an optical biosensor (BIAcore) for determining th e presence of sulfamethazine (SMT) residues in pig bile was developed. The assay was used in a routine screening laboratory alongside a previously des cribed biosensor method for sulfadiazine (SDZ). Sulfonamide bile concentrat ions, determined by enzyme immunoassay (EIA), have already been shown suita ble for use in predicting the extent of sulfonamide accumulation in kidney. The ability of immunobiosensor based bile screening to predict violative t issue residues (greater than the maximum residue limit; MRL) was compared w ith results achieved using two conventional EIAs for two of these drug resi dues (SMT and SDZ). Analysis of 2081 samples for both sulphonamide residues , over an 8 month period, showed the false positive prediction rate of bios ensor analysis to be 0.14% and 0.34% for SMT and SDZ, respectively, compare d with false positive rates of 1.54% and 1.44% by EIA. Biosensor analysis s howed no false negative predictions for either SMT or SDZ while ELA showed a false negative prediction rate of 0.14% for SMT and 0.24% for SDZ. The pr esent study has clearly demonstrated that immunobiosensor assays can be dev eloped for veterinary drug residue screening programmes. These methods have the potential for generating faster and more reliable results than convent ional immunoassay methods.