I have few questions regarding the use of Kirby Bauer method versus E-test for AST. As per CLSI guidelines, for certain drugs like vancomycin, methicillin, colistin, etc, we are supposed to report MIC rather than zone of inhibition in a diagnostic set-up. The reason for this is that these molecules are bigger in size and hence their diffusion on agar is poor. Since MIC by broth dilution is laborious and also requires technical expertise in clinical diagnostic labs, E-test is adopted in many places. Now E-test though reports MIC still works on the same principle of agar diffusion. So, is E-test really reliable over the MIC broth dilution in a diagnostic laboratory set-up? Additionally, if the diffusion ability of these drugs undermine the accuracy of the disc diffusion method, would the experiments done to calculate the sensitive / intermediate / resistant break points not compensate for that lacuna? Thank you.