Hello, 3M staffers found this for your consideration:
From the <span style=”text-decoration: underline;”>Manual of Clinical Microbiology, 8<sup>th</sup> Edition, 2003 pg. 1158-1159 </span>:
“Methods that are commonly used to test rapidly growing aerobic and facultative anaerobic bacteria are, for a variety of reasons, unsuitable for testing most mycobacterial species. For example, the conventional disk diffusion method is not suitable for testing slowly growing mycobacteria because the drug diffuses throughout the medium before growth of the mycobacteria is significantly affected. The methods generally accepted for determining the antimicrobial susceptibility of mycobacteria are based on the growth of the microorganisms on solid or in liquid medium containing a specified concentration of a single drug.”
“Based on the current NCCLS guidelines, a rapid susceptibility testing method should be used in conjunction with rapid methods of primary culture and identification to allow the earliest possible detection of resistance.”
Sorry for the ancient reference but it should suffice because organism growth rates still determine the testing method. Generally, all susceptibility methods are used based on CLSI (formerly NCCLS) guidelines to which the public and IHTSDO do not have access. They are a purchased set of guidelines. The Mayo reference below is the best I can find as it actually references the CLSI guidelines.
There are rapid methods for susceptibility testing on Mtbc (a slow-growing organism) now also based on other reading so if we ever get AFB drugs for mapping, it behooves us to ask the method of testing.