Mueller-Hinton agar

Mueller-Hinton agar is a microbiological growth medium that is commonly used for antibiotic susceptibility testing. It is also used to isolate and maintain Neisseria and Moraxella species.

Colonies of Burkholderia pseudomallei on Müller-Hinton agar after 72 hours incubation.

It typically contains:

2.0 g beef extract
17.5 g casein hydrolysate
1.5 g starch
17.0 g agar
1 liter of distilled water.
pH adjusted to neutral at 25 °C.[1]

Five percent sheep blood and nicotinamide adenine dinucleotide may also be added when susceptibility testing is done on Streptococcus species. This type is also commonly used for susceptibility testing of Campylobacter.

It has a few properties that make it excellent for antibiotic use. First of all, it is a nonselective, nondifferential medium. This means that almost all organisms plated on it will grow. Additionally, it contains starch. Starch is known to absorb toxins released from bacteria, so that they cannot interfere with the antibiotics. Second, it is a loose agar. This allows for better diffusion of the antibiotics than most other plates. A better diffusion leads to a truer zone of inhibition.

Mueller-Hinton agar was co-developed by microbiologist John Howard Mueller and veterinary scientist Jane Hinton at Harvard university as a culture for gonococcus and meningococcus, who published the method in 1941.[2]

References

"Susceptibility testing of Salmonella using disk diffusion" (PDF). World Health Organization. July 2002. p. 9. Retrieved 12 May 2016.
Mueller, J. H.; Hinton, J. (1 October 1941). "A Protein-Free Medium for Primary Isolation of the Gonococcus and Meningococcus". Experimental Biology and Medicine. 48 (1): 330–333. doi:10.3181/00379727-48-13311.

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[1] "Susceptibility testing of Salmonella using disk diffusion" (PDF). World Health Organization. July 2002. p. 9. Retrieved 12 May 2016.

[Mueller_&_Hinton_1941-2] Mueller, J. H.; Hinton, J. (1 October 1941). "A Protein-Free Medium for Primary Isolation of the Gonococcus and Meningococcus". Experimental Biology and Medicine. 48 (1): 330–333. doi:10.3181/00379727-48-13311.