Applicability of various microbial inhibitor tests as screening tests for the presence of antimicrobials in goat and ewe milk

摘要

The applicability (specificity, sensitivity) of commercial and non-commercial inhibitor tests with B. stearothermophilus var. calidolactis (Delvotest SP, BR-Test "AS-Special", BRT-lnhibitorTest without prediffusion, BRT MRL-Screening Test, conventional disk assay, disk assay modified with a dialysis membrane) for goat (n = 181) and ewe milk (n-242) was determined. For the evaluation only samples producing no inhibition zones or showing a complete colour change were interpreted as negative. Under thiscondition the disk assay with dialysis membrane (MWCO 12,000-14,000) showed the highest specificity but a slightly inferior sensitivity than the Delvotest SP and the BR-Test "AS-Special". If cow milk was used as negative control the rate of "false positives" was 3,15,96 and 100% for goat milk, and 52,6, and 92% for ewe milk using the Deivotest SP, BR-Test "AS-Special", the BRT-lnhibitor Test without prediffusion and the BRT MRL-Screening Test, respectively. The percentage of false-positive reactions could, however, be decreased by prolongation of the incubation time. A prolongation of 30 min resulted In a rate of "false positives" less than 2% for milk from both species using the Delvotest SP and BR-Test "AS-Special", respectively.