Antimicrobial vs. Antibacterial

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will define antimicrobial and antibacterial. You'll learn how the two terms are similar and how their definitions, while at surface value are easy, are a bit more nuanced than most people assume.

Similar but Different Terms

Would you say that something like boat and a yacht are the same thing? Yes and no. After all, both float in the water! Both are really enjoyed only on the very first and very last day an owner has one. But they're not exactly the same because boat is an all-encompassing term and a yacht is a type of boat used for noncommercial purposes.

Well, the same line of thinking can be used to explain the differences between antimicrobial and antibacterial. They are sort of the same, but not exactly. Let's find out how in this lesson.


An antimicrobial is an agent that inhibits the growth of a microorganism or kills such an organism outright. 'Anti-' stands for 'against' and a microbe is a microorganism, a microscopic organism.

What is a microscopic organism? That sounds like a really simple question that any scientist can rattle off the answer to. Alas, when you dig deeper, it's not. There's more than one reason for this and we'll get to that in a second.

In the very broadest and most common description of a microorganism, we can include the following:

  • Bacteria
  • Fungi
  • Parasites, including protozoa
  • Viruses

In some people's views, prions, which are disease-causing proteins, are also microorganisms. These aren't commonly included in most definitions, however.

In any case, there's a problem with using such a broad approach to defining a microbe if we're going to nitpick things. First, we when we say microbe (microorganism) we use the prefix of 'micro-' which denotes something very little or microscopic, or invisible to the naked eye. The problem? Some bacteria, such as Thiomargarita namibiensis, as well as many types of fungi and parasites can easily be seen with the naked eye!

Another problem? When we say microorganism, the suffix of '-organism' denotes some sort of form of life. Well, prions are not a form of life and many scientists argue (for reasons beyond this lesson's scope) that viruses aren't a form of life either.

There's also another twist. In the field of medicine, when we refer to a microbe, we are often implying the fact that it isn't any old microscopic organism. Specifically, it is one that is pathogenic, which means it has the ability to cause disease in a person. This is why we develop countermeasures against ('anti-') these microbes.

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