[Residues of inhibitory agents in the tissues of slaughter-house animals--comparison of microbiological methods of agar diffusion].

Three microbiological methods of agar diffusion were compared which are used to detect the residues of inhibitory substances: method using the strain Bacillus subtilis ATCC 6633 (B.s. 6633), method using the strain Bacillus stearothermophilus v. calidolactis C 953 (B. s. v. c. 953), and four-plate method. Using the compared methods, minimum inhibitory concentrations were determined for standard solutions of antibiotics and sulphadimidine. Inhibitory substances were detected parallely in the samples of the tissues of medicated and emergency-slaughtered animals, applying the three compared methods. In indicated cases inhibitory substances were identified by electrophoresis and chemical methods. The results indicate the following: 1) The B.s. 6633 method is the least sensitive of all to the residues of inhibitory substances. 2) For the purposes of detection of most antibiotics under investigation, the B.s.v.c. 953 method and the four-plate method are replaceable. The B.s.v.c. 953 method is more suitable for the detection of penicillin residues, in the case of tetracycline antibiotics it is the four-plate method. 3) Sulphadimidine residues can be detected only by the four-plate method. 4) The four-plate method enables to make the preliminary group identification of antibiotics and sulphonamides. 5) The detection limit of microbiological methods is not sufficiently sensitive to determine chloramphenicol residues; that is why the physico-chemical methods must be used.