Disc diffusion test by scaled Petri dish

Aims: As a result of several factors such as excessive use of drug, bacteria can resist against antibiotics. Anti- biogram test is used to assess the antibiotic or the other antimicrobial agents' ability in prevention from bacteria's growth in laboratory. Based on the CLSI data in January 2006, regarding the disc diffusion test, the effect of 92 antibiotics have been evaluated with 329 different tests with different bacteria. Common standard disc dispensing is carried out with 15mm distance from the plate border. The aim of the study was to introduce a new tool for measuring the microorganisms' sensitivity to antibiotics. Materials & Methods: In the graded new plate and its using method, disc dispensing was done without any distance from plate border and using a full or half-disk. Results: The lack of distance from plate border, not only had no negative effect on the results but also led to the higher accuracy and reduction of problems and errors and unwanted interference in the previous methods. Conclusion: The use of this plate and its method increases the efficiency of the disc diffusion test between 3- 17% in the plates with standard sizes of 84-120 mm.