Antimicrobial Resistance: Causes, Types & Examples

Instructor: Amanda Robb

Amanda has taught high school Biology & Physics for 8 years. She received her M.Ed. from Simmon's College and M.S. from Tufts in Cellular and Molecular Physiology.

In this lesson, we'll be exploring the important topic of antimicrobial resistance. We'll cover what is causing this global problem and explore types and examples of antimicrobial resistance.

What Is Antimicrobial Resistance?

Prior to the 1930s, a simple bacteria infection could be deadly. Soldiers with battle wounds from World War I were at the mercy of bacteria. Wounds festered and infection spread. This all changed in 1928 when Dr. Alexander Fleming discovered penicillin, a type of antibiotic. This chemical was naturally produced by fungi and killed bacteria. Today, bacterial infections are treated with a range of antibiotics and are easily cleared up by your physician.

Similarly, medications have been developed to combat other microbes or microscopic organisms, such as viruses, parasites and fungi. But as we wage our war on microbes, microbes fight back. Most microbes reproduce very quickly due to their small size. To understand how this strategy helps them evade our antimicrobial drugs, or drugs that kill microbes, let's go back and review cell reproduction.

Every time a cell needs to divide it must copy its DNA. When doing this, sometimes mutations occur that change the DNA. These mutations can sometimes be beneficial and confer resistance to the antimicrobials. When the microbes are exposed to antimicrobials all of the microbes die, except the ones with genes for antimicrobial resistance. These microbes survive and reproduce and soon the entire population is antimicrobial resistant.

Types of Antimicrobials

Bacterial

Bacteria are killed by a specific type of antimicrobial called antibiotics. Antibiotic resistance is a becoming major medical crisis in the world. In addition to random mutations, bacteria have another way to acquire antibiotic resistance, called plasmids. Plasmids are small circular pieces of DNA outside the genome. Often plasmids contain genes for antibiotic resistance and toxins. Bacteria trade these plasmids like collectors cards, swapping genes that increase illness. One bacteria with a plasmid for antibiotic resistance can quickly spread it to the rest of a population.

The emergence of antibiotic resistance is a product of human behavior. The more antibiotics are used, the more bacteria become resistant to them. For example, antibiotics are often prescribed for viral infections, in which they do not work. Livestock are treated with antibiotics to prevent infections. Even hand soaps contain antibiotics! The more we use antibiotics, the more resistance will emerge.

Example: MRSA

One of the most famous examples of antibiotic resistance is methicillin-resistant Staphylococcus aureus (MRSA). This so called super-bug is resistant to many antibiotics and has become a major issue in health care.

MRSA is resistant to many types of antibiotics
MRSA

MRSA causes staph infections, which usually infect the skin but can spread to other parts of the body as well, causing sepsis and eventually death. It can be very difficult to treat due to antibiotic resistance. MRSA is a rampant cause of secondary infections in hospitals, and can also be found in communities where people share towels, mats, equipment or have other skin to skin contact.

Viral

Viruses are non-living infectious particles that cause disease. These pathogens require a host cell to reproduce. Once inside, they infect host cells and hijack the host cell machinery, forcing the cell to make more viruses. Viruses reproduce incredibly quickly, much faster than cells. The faster the virus reproduces, the greater the chances of it acquiring a mutation for antiviral resistance. Thus, viruses acquire resistance much faster than bacteria.

HIV

Human immunodeficiency virus (HIV) infects immune cells called T-cells. Left untreated it can destroy the immune system, making the patient susceptible to other infections. HIV patients often die of secondary infections like pneumonia. HIV is tricky because it accumulates mutations faster than other types of viruses, meaning it can quickly evolve antiviral resistance.

HIV shown in yellow infects a T-cell shown in blue
HIV

As the virus evolves, the originally prescribed antiviral drugs can no longer control the infection, and HIV starts to take hold again. Antiviral resistance sometimes allows HIV to become resistant to all antivirals in a particular class, even if the person has never taken them. Strict adherence to medication is one way to help prevent antiviral resistance.

Parasitic

Unlike the tiny HIV particles, parasites are much larger. They can range from a single cell to macroscopic multicellular organisms. Parasites are organisms that depend on a host for nutrients and are harmful to the host.

Malaria

Malaria is the most common parasitic infection in the world and is responsible for hundreds of thousands of death each year, particularly in sub-Saharan Africa. Malaria is caused by four members of Plasmodium species. These parasites are transmitted through mosquito bites.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account
Support