Published: 23rd Jul 2025, 16:34

In 2019, the CDC published a report, Antibiotic Resistance Threats in the United States, 2019 (AR Threat Report), stating that AMR bacteria and fungi caused at least 2,868,700 infections and 35,000 deaths each year.
Let that sink in – at least. The numbers aren’t just alarming—they are a clear signal of a looming emerging global public health emergency demanding immediate action: Antimicrobial Resistance.

It’s not a distant threat. It’s happening now. Furthermore, it’s a battle where prevention is more urgent and effective than a cure. But how do we detect and respond to antibiotic resistance? 

That is where Microbiology comes into action, and MHA becomes our warrior at the forefront. 

This blog is the saga of mueller hinton agar in a world with ever-rising threats of AMR and superbugs, highlighting its importance and role in fighting villains on the rise.

The Rise of MHA?

It was the early 1940s, and a new storm was gathering under the lenses of microscopes.

Neisseria, a cunning genius of the microscopic world, was proving to be one of the deadliest villains on the rise. Gonorrhea and Meningitis weren’t just some names on the charts anymore. Antibiotics were the new hope. But we had to plan something to isolate and test which one would work- the world needed to fight back.

In 1941, two scientists, John Howard Mueller and Jane Hinton, while studying Neisseria species at Harvard, realized something critical: the world needed a reliable, consistent medium to grow and test these microbes.

And so, mueller hinton agar was developed.

Primarily, Mueller and Hinton introduced it just as a non-selective, non-differential nutritional base to support the growth of Neisseria. But over time, it became much more. It was when two scientists, Kirby and Bauer, suggested it as a medium for performing Antimicrobial Susceptibility Test using discs impregnated with standardized concentration (defined amounts as per CLSI/EUCAST protocols to reflect therapeutic levels) of antimicrobial compounds, and it became a universal testing ground where antibiotics would be put to the test and resistance could be tracked.

The medium’s performance complies with the requirements and standards of the Clinical and Laboratory Standards Institute (CLSI), formerly NCCLS, and the WHO, FDA, and EDUCAST. MHA has been selected by the CLSI for several reasons:

1. Demonstration of good batch-to-batch reproducibility for AST (Antimicrobial Susceptibility Testing)
2. For having a low concentration of inhibitors (e.g, Sulfonamides, Trimethoprim, and Tetracycline)
3. Supports the growth of most non-fastidious bacterial pathogens.

The WHO Committee on Standardization of Susceptibility Testing has accepted mueller hinton agar for determining the susceptibility of microorganisms, mainly because of its reproducibility. 

Composition and Preparation of MHA

Final pH adjusted to 7.3 +/- 0.1

The Principle of MHA:

The main contents of Mueller Hinton Agar include Caesin acid hydrolysate, Beef infusion, Starch, and Agar, which provide essential nutrients to the enrichment medium. The contents with nutrients they provide are mentioned below:

• Casein Acid Hydrolysate: It is essentially a rich source of Amino Acids and Nitrogen.
• Beef Infusion: Added as a source of Nitrogen, Vitamins, Amino Acids, and other essential nutrients.
• Starch: Is a Carbon source and a colloid that absorbs any toxins produced.
• Agar: Solidifying Agent

To confer consistent zones of inhibition as per specified diameters in the CLSI standards (specified under certain pH, moisture, density and incubation time), the medium is formulated with controlled levels of thymidine, thymine, calcium, and magnesium to prevent interference with the activity of certain antibiotics (e.g., sulfonamides, trimethoprim, tetracyclines, and aminoglycosides).

Preparation of Mueller Hinton Agar (MHA):

TM Media’s mueller hinton agar (Product Code: TMP 005) is ready-to-use, sterile microbiological media plates, sealed for assured quality and reliability. But just in case you want to make it from scratch, the details (Product Code: TM-339) are mentioned below:

• Dissolve 38.0 grams in 1000 ml purified/distilled water.  
• Heat to boiling to dissolve the medium completely.  
• Sterilize by autoclaving at 15 psi pressure (121°C) for 15 minutes.  
• Cool to 45-50°C.
• Mix well and pour into sterile Petri plates.

Quality Control Specifications:

Results/Interpretations on MHA (Product Code: TMP 005):

Cultural characteristics observed after cultivation on MHA plates are as follows:

Mueller Hinton Agar Plates (Product Code: TMP 005) can also be used for Antimicrobial Susceptibility Testing (AST), using both the Kirby-Bauer disk diffusion and Minimum Inhibitory Concentration (MIC) methods. The diameters of the zones of inhibition hence formed can be measured to determine whether a given microorganism is susceptible, intermediate, or resistant to a specific antibiotic. For interpretations, the product data sheet can be used for reference.

Mueller Hinton Agar Uses:

• Cultivation and Isolation of Neisseria species.
• For Antimicrobial Susceptibility Testing (AST) 
• The FDA’s Bacteriological Analytical Manual also lists its uses for food testing, particularly for working with aerobic and facultative anaerobic bacteria.

Why Use TM Media’s MHA Agar Plates:

1. TM Media’s MHA Agar Plates (Product Code: TMP 005) offer a convenient ready-to-use option in a world where you need to be faster than the division of bacteria.
2. Our ready-to-use, quality-sealed plates are not only time-efficient but also ensure a sterile and contamination-free laboratory experience.
3. We meet Clinical and Laboratory Standards Institute’s (CLSI) guidelines for reliable AST results.
4. We offer consistent batch-to-batch reproducible results and consistent zones of inhibition for bacteria and mistakes.
5. TM Media’s MHA Agar Plate (Product Code: TMP 005) supports the growth of most non-fastidious, aerobic, and facultative microbes.
6. Our ready-to-use plates don’t just meet the highest standards of safety but are also reliable for food and clinical microbiology applications.

Frequently Asked Questions (FAQs)