4.2 How the test organism determines the method used
Disk diffusion is good for organisms such as Staphylococci and Enterobacterales, which grow well under standard conditions and in a 24-hour time frame.
Disk diffusion tests are not routinely used with microorganisms such as mycobacteria, fungi and some anaerobes. Why is that?
Disk diffusion is not suitable for slow-growing organisms such as mycobacteria and fungi, or for some with very fastidious growth requirements.
These organisms are not able to produce readable growth within the time frame on a standard agar plate. The antibiotic may have all diffused out of the agar or even degraded by the time growth becomes visible. Fungi are also problematic because some species spread hyphae, fruiting bodies and spores all over the plate. They need different techniques such as broth dilution or microdilution instead.
4.1 Advantages and disadvantages of different types of test in practice
