Why MHA is used for antibiotic susceptibility testing?

  1. It is a non-selective, non-differential medium. This means that almost all organisms plated on here will grow.
  2. It contains starch. Starch is known to absorb toxins released from bacteria, so that they cannot interfere with the antibiotics. It also mediates the rate of diffusion of the antibiotics through the agar.
  3. 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.
  4. MHA shows acceptable batch-to-batch reproducibility for susceptibility testing.
  5. MHA is low in sulfonamide, trimethoprim, and tetracycline inhibitors (i.e. concentration of inhibitors thymidine and thymine is low in MHA).
  6. Both the para-aminobenzoic acid (PABA) and thymine/thymidine content in Mueller Hinton Agar are reduced to a minimum, thus markedly reducing the inactivation of sulfonamides and trimethoprim when the media is used for testing the susceptibility of bacterial isolates to these antimicrobics.

Sagar Aryal

Hi, my name is Sagar Aryal and I am a passionate Microbiologist and the Scientific Blogger. I am currently studying M.Sc. Microbiology Thesis Year at St. Xavier's College, Kathmandu, Nepal. I am particularly interested in research related to Medical Microbiology and Virology.

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