Mannitol Salt Agar For The Isolation Of Staphylococcus Aureus

The science researcher’s toolbox is as vast and complex as it is head spinning and hard for newcomers and novices to wrap their heads around.

With what feels like a thousand different types and pieces of equipment that can be used for twice as many different tests and experiments, it is certainly no small task to learn and understand even a fraction of them.

Take Mannitol salt, for instance. Understanding how even a single growth medium is used, as well as the kind of tests it is used for, can feel very overwhelming to a newcomer.

Mannitol Salt Agar For The Isolation Of Staphylococcus Aureus

The statement: ‘Mannitol salt agar is used in the preparation and isolation of the bacterium Staphylococcus Aureus can feel like complete jargon to someone who isn’t caught up on their scientific terms.

Well, that is what this article is for.

Not only are we going to explain what exactly the previous statement means, but we’re also going to help you understand what these two items in a scientist and researcher’s catalog are, as well as further details on what this test entails.

What Is Mannitol Salt Agar?

Before we even begin to tackle what the title of this article means, we should first probably try to explain what exactly Mannitol salt agar is, as well as what it is made from.

Putting it simply, Mannitol salt agar is a growth medium that is most often used in the field of microbiology, the study of microscopic organisms and other life, as well as examining biological and biochemical processes that take place at this tiny scale.

You may be familiar with the term ‘growth medium’, even in just passing, perhaps from some memory of studying the sciences in school or education, and it is exactly what it sounds like.

A growth medium is a medium that is specifically designed or cultivated to help support the growth of microorganisms so that they can be further studied in a laboratory setting.

This medium can come as either a solid, a liquid, or even a semi-solid substance.

So long as it helps sustain or propagate microbiological life, it is an effective growth medium.

As we briefly touched on, growth mediums are often designed to help cater to the growth of a particular type of organism, leading to a wide array of different types of growth mediums.

Mannitol salt agar is one such example. As the name would suggest, mannitol salt has a high amount of salt in its makeup, around 7-10%.

As many bacteria cannot survive high levels like this very well, Mannitol salt agar is great for cultivating species that have high salt tolerance.

The Uses Of Mannitol Salt

This growth medium has a surprising amount of versatility to it, being used for several purposes. It is used in the enumeration of bacteria such as Staphylococcus in a wide array of food products, more specifically dairy items.

It is also a growth medium that is used in the testing of cosmetics by several organizations, including the Food and Drug Administration (FDA) and their Bacteriological Analytical Manual.

It is also quiet for testing the membrane filtration of water items used in many public spaces, such as at spas, in swimming pool water, and even in drinking water faucets and fountains.

And, of course, it is used in scientific tests to selectively isolate and differentiate between certain salt-tolerant bacteria, including the species that are mentioned in the title of this article: Staphylococcus Aureus.

What Is Staphylococcus Aureus?

What Is Staphylococcus Aureus?

It is probably a good point to now explain what exactly this bacteria is and what it does, and why it is worth isolating and studying.

Also known more commonly as staph, Staphylococcus is part of the family of bacteria known as Bacillota, known for having cell walls that will react positively to the Gram Stain test, also being called gram-positive bacteria.

Staph is most often found in the respiratory tract of about 30% of human beings, usually in the nose.

Whilst these bacteria are harmless to people in most cases, it is also known for being what is known as an opportunistic pathogen in some examples, meaning that it can become a serious health issue in situations where a person’s immune system is otherwise weakened, becoming what is more widely known as a staph infection.

Staph infections can manifest in several serious health risks, several of which can be fatal if left untreated.

Many of these, such as pneumonia or endocarditis, are the result of staph infections reaching vital organs like the heart or lungs and can cause conditions such as heart failure or lung disease, and even strokes.

Needless to say, being able to identify samples of staph pathogens is a vital health test that can be carried out on people with unidentified health issues and is an incredibly important test that can potentially save lives.

Preparing Mannitol Salt Agar For Isolating Staphylococcus Aureus

So, now that we have explained what exactly this particular growth medium and bacteria do, it is time to outline how exactly Mannitol salt agar is prepared for testing whatever bacteria culture you are examining.

  • Preparation would start by suspending a decent amount of this growth medium in distilled water. For a measurable amount, you should add approximately 111.025gm of Mannitol salt agar for every 1000ml of distilled water you are using.
  • You then need to boil the mixture together until the growth medium has dissolved into the water completely.
  • Once you have finished boiling, you would then place this solution in an autoclave, and maintain a temperature of around 249.8 degrees Fahrenheit (or 121 degrees Celsius) for between 15 to 20 minutes.
  • Once this has finished, you would then allow the solution to cool down to 113 to 122 degrees Fahrenheit (or 45 to 50 degrees Celsius), before pouring it into a petri dish. Now it is ready for your bacteria culture to be applied.

What Results You Can Expect

What happens after you apply your bacteria colony to this solution will vary depending on what type you have.

  • The presence of Staphylococcus Aureus will turn the bacteria colonies well, as well as the solution.
  • Staphylococcus bacteria that are not the subspecies aureus will either leave the solution colorless or turn it and its colonies red.
  • Any Micrococci bacteria detected will result in white or orange colored colonies.
  • Most other bacteria will not change the solution’s color.

Final Thoughts

So, having read through this article, you should now be able to understand why this test, and especially detecting these bacteria with this growth medium, are such important tests for you as a researcher to understand.

Now you’re ready to test and see the results for yourself!

Jennifer Dawkins