Dear Mitesh Shrestha

In this, test disks of third-generation cephalosporins and augmentin are kept 30 mm apart, center to center, on inoculated Mueller-Hinton agar (MHA). A clear extension of the edge of the inhibition zone of cephalosporin towards augmentin disk is interpreted as positive for ESBL production. Evaluations of the double-disk diffusion test have revealed sensitivities of the method ranging from 79% to 97% and specificities ranging from 94% to 100%. While the double-disk diffusion test is technically simple, the interpretation of the test is quite subjective. Sensitivity may be reduced when ESBL activity is very low, leading to wide zones of inhibition around the cephalosporin and aztreonam disks, especially for Proteus mirabilis.False-negative results have been observed with isolates harboring SHV-2, SHV-3or TEM-12. In isolates which are suspicious for harboring ESBLs but are negative using the standard distance of 30 mm between disks, the test should be repeated using closer (for example, 20 mm) or more distant (for example, 40 mm) spacing

Kindly follow links below for some suggestions

https://www.ncbi.nlm.nih.gov/pubmed/9598782

Article Extended-spectrum β-lactamases in Gram Negative Bacteria

Dear Shrestha

Double disk synergy test is used for confirmatory detection of extended spectrum beta-lactamases using third generation cephalosporins and Clavulanate. The later, clavulanate will do as beta-lactamase inhibitor and if the 3rd generation cephalosporins produces ESBL , it will produce zone of inhibition toward clavulanate and give a unique shape on agar plate e.g., Muller Hinton Agar.....Best regard

Hi'

Double-disk synergy test for detection of synergistic effect between antibiotics against nosocomial strains of staphylococcus aureus

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4076852/

Dear Mitesh Shrestha

In this, test disks of third-generation cephalosporins and augmentin are kept 30 mm apart, center to center, on inoculated Mueller-Hinton agar (MHA). A clear extension of the edge of the inhibition zone of cephalosporin towards augmentin disk is interpreted as positive for ESBL production. Evaluations of the double-disk diffusion test have revealed sensitivities of the method ranging from 79% to 97% and specificities ranging from 94% to 100%. While the double-disk diffusion test is technically simple, the interpretation of the test is quite subjective. Sensitivity may be reduced when ESBL activity is very low, leading to wide zones of inhibition around the cephalosporin and aztreonam disks, especially for Proteus mirabilis.False-negative results have been observed with isolates harboring SHV-2, SHV-3or TEM-12. In isolates which are suspicious for harboring ESBLs but are negative using the standard distance of 30 mm between disks, the test should be repeated using closer (for example, 20 mm) or more distant (for example, 40 mm) spacing

Kindly follow links below for some suggestions

https://www.ncbi.nlm.nih.gov/pubmed/9598782

Article Extended-spectrum β-lactamases in Gram Negative Bacteria

Thank you all very much for the answer..

The principle is that the ESBL produce enzyme that destroy betalactam antibiotic. That enzyme is inhibited by acid clavulanic and restore the activity of the betalactam antibiotic. In the synergy test, what hapenned is that the clavulanic acid in Amoxicillin-clavulanic acid inhibit betalatamase and the Cephalosporin become active on the bacterial and the diameter of inhibition becomes wider.