Use of sensitivity discs as primary antibiotic standards in MIC determination.

A method for the determination of minimum inhibitory concentration (MICs) is described, in which commercially prepared antibiotic sensitivity testing discs are used as primary antibiotic standards from which the necessary dilutions are prepared in WHO Perspex haemagglutination plates. The materials required are readily available in most laboratories at a cost in time and reagents that compares favourably with most traditional methods of MIC testing. The same techniques may also be used to demonstrate combined antibiotic activity and to differentiate between bacteriostatic and bactericidal activity, with little expenditure of laboratory resources.