What is the Difference Between Nutrient Agar and Mueller Hinton Agar

The key difference between nutrient agar and Mueller Hinton agar is that nutrient agar is a media mainly used for the general isolation of bacteria, while Mueller Hinton agar is a media used for antibiotic susceptibility testing of bacteria.

Microbial media play an important role in the successful isolation of microorganisms. Media can be categorized as general-purpose media, differential media, and selective media. General purpose media can be used to isolate any microorganism, while selective and differential media is used for specific isolation of microorganisms. Nutrient agar generally isolates all bacteria from a particular source, while Mueller Hinton agar is most suited for antibiotic susceptibility testing.

CONTENTS

1. Overview and Key Difference
2. What is Nutrient Agar 
3. What is Mueller Hinton Agar
4. Similarities – Nutrient Agar and Mueller Hinton Agar
5. Nutrient Agar vs Mueller Hinton Agar in Tabular Form
6. Summary – Nutrient Agar vs Mueller Hinton Agar

What is Nutrient Agar?

Nutrient agar is the main growth media used for the isolation of a wide range of bacteria from various sources. It may also promote fungal growth, but the growth is limited due to the high pH of the nutrient agar media. Nutrient agar is a solid medium. The main components of nutrient agar include peptone, beef/yeast extract, sodium chloride, water, and agar. In this medium, agar acts as the solidifying agent. The overall pH of the medium is adjusted to 7.4 before sterilization. Peptone acts as the primary source of protein by supplying organic nitrogen, while beef extract supplies water-soluble macro and micronutrients. Sodium chloride maintains the ionic balance of the media, and water provides the medium for microbial growth.

The ready-to-use nutrient agar medium will require dissolving 28g of nutrient agar in 1 liter of water, following which the media, along with the Petri dishes, will be sterilized and poured accordingly. The inoculation is performed after the medium is completely solidified. Nutrient agar’s main use is the isolation of bacteria. Further, nutrient agar can also be used during bacterial preservation and to develop bacterial lawns for further research.

What is Mueller Hinton Agar?

Mueller Hinton agar medium was first developed by Mueller and Hinton, and at present, the medium is mainly used for antibiotic susceptibility due to its unique features. This medium is most suited for the Kirby Bauer method of antibiotic susceptibility testing. The overall pH is maintained at 7.3, and the main components of the medium include beef extract, casein hydrolysate, starch, distilled water, and agar. Agar is used as the key solidifying agent in the medium preparation.

The principle behind the use of Mueller Hinton agar is based on the fact that the medium is poor in sulfonamides, trimethoprim, and tetracycline inhibitors, which allow the growth of non-demanding pathogens during antibiotic susceptibility testing. The primary application of Mueller Hinton agar is to facilitate antimicrobial susceptibility tests through the Kirby Bauer method. Moreover, it is also used for specific isolation of Neisseria. Under the FDA bacteriological analytical manual, Mueller Hinton agar is widely used to perform test experiments on aerobic and facultative anaerobic bacteria.

What are the Similarities Between Nutrient Agar and Mueller Hinton Agar?

• Nutrient agar and Mueller Hinton agar are solid media.
• Both nutrient agar and Mueller Hinton agar facilitate the growth of bacteria.
• Both media contain beef extract as a medium component.
• Moreover, the pH of both media is 7.3.

What is the Difference Between Nutrient Agar and Mueller Hinton Agar?

Nutrient agar is a medium mainly used for the general isolation of bacteria, while Mueller Hinton agar is a medium used for antibiotic susceptibility testing of bacteria. Thus, this is the key difference between nutrient agar and Mueller Hinton agar. Casein hydrolysate is absent in nutrient agar, while it is present in Mueller Hinton agar. Moreover, sodium chloride is present in nutrient agar but is absent in Mueller Hinton agar.

The below infographic presents the differences between nutrient agar and Mueller Hinton agar in tabular form for side-by-side comparison.

Summary – Nutrient Agar vs Mueller Hinton Agar

Growth media are essential for the isolation and culturing of microorganisms. Nutrient agar and Mueller Hinton agar are two types of culture media used in bacteriology. Nutrient agar is mainly used for the general isolation of bacteria. Mueller Hinton agar is used for antibiotic susceptibility testing of bacteria. They are solid media that contains agar as the main solidification agent. Even though the media components vary between the two media, beef extract and water are present in both media. So, this summarizes the difference between nutrient agar and Mueller Hinton agar.

Reference:

1. Aryal, Sagar, et al. “Mueller Hinton Agar (MHA) – Composition, Principle, Uses and Preparation.” Microbiology Info.com, 10 Aug. 2022.
2. Aryal, Sagar, et al. “Nutrient Agar: Composition, Preparation and Uses.” Microbiology Info.com, 10 Aug. 2022.

Image Courtesy:

1. “Roseomonas gilardii growing on Nutrient Agar” By Nathan Reading (CC BY-NC-ND 2.0) via Flickr
2. “BpsMH” By Gak – Own work (CC BY-SA 3.0) via Commons Wikimedia