[Methodological approaches to controlling the antibiotic content in disks for determining microorganism antibiotic...

The content of antibiotics in the discs is the main requirement to their quality. There are 2 methods for determination of the antibiotic content in the discs: (1) a method with preliminary extraction of the antibiotic from the disc followed by determination of its content in the extract biologically and (2) a method using 3 or more standard discs containing different amounts of the antibiotic. A study was performed to show the advantages and limitations of the methods. The conditions for determination of the activity of 22 antibiotics contained in the discs with the method using the standard discs were developed. Comparison of the results obtained with the 2 methods showed that they did not differ significantly. However, it is considered advisable to use for the disc control the method based on direct diffusion of the antibiotic from the disc into agar, since in this case the antibiotic amount in the disc is determined under conditions as much as possible close to the conditions of the disc using for determination of the microbial antibiotic sensitivity.