Evaluation of the Swab Test on Premises, the Calf Antibiotic and Sulfa Test, and a Microbial Inhibitor Test with Standard Solutions of 22 Antibiotics

Abstract

The sensitivities of the Swab Test on Premises (STOP), the Calf Antibiotic and Sulfa Test (CAST) and a laboratory Microbial Inhibitor Test (MIT) previously used for confirmation of STOP results were compared. Different media were compared for the STOP and MIT. The CAST was more sensitive than the STOP for the 22 antibiotics tested. The sensitivity of the STOP procedure increased for 15 of the 22 antibiotics tested when the standard STOP medium, Antibiotic Medium No. 5 (AM-5), was replaced with Saskatoon Antibiotic Medium-3 (SAM-3), the medium used for thin-layer bioautography. When Antibiotic Medium No. 2 (AM-2) was used in the STOP procedure, the overall sensitivity was intermediate between that obtained using AM-5 and SAM-3. For the MIT, Micrococcus luteus ATCC 9341 provided greater sensitivity as a test organism than Bacillus cereus ATCC 11778 for 16 antibiotics and was less sensitive for 4 antibiotics, particularly chlortetracycline, oxytetracycline and tetracycline. M. luteus ATCC 9341 was notably more sensitive as a test organism for bacitracin and lincomycin than was B. cereus ATCC 11778.