9.2 Basic Concepts
Open Resources for Nursing (Open RN)
Normal Flora and Microbiome
Microorganisms occur naturally and are present everywhere in our environment. Some microorganisms live on the skin, in the nasopharynx, and in the gastrointestinal tract, but don’t become an infection unless the host becomes susceptible. These microorganisms are called normal flora. Over the past several years, it has been discovered that every human being carries their own individual suite of microorganisms in and on their body referred to as their microbiome. A person’s microbiome is acquired at birth and evolves over their lifetime. It is different across body sites and between individuals. A person’s gut microbiome has recently been found to impact their immune system.[1],[2]
Pathogens
Microorganisms that cause disease are called pathogens. There are four common types of pathogens, including viruses, bacteria, fungi, and parasites.
After a host (i.e., the person) becomes infected by a virus, the virus invades the body’s cells and uses the components of the cell to replicate and produce more viruses. After the virus replication cycle is complete, the new viruses are released into the body, causing damage or destruction of the host’s cells.[3]
Antiviral medications can be used to treat some viral infections. Antibiotics do not kill viruses and are ineffective as a treatment for viral infections. See Figure 9.1[4] for an image of a virus.
Read additional information about antiviral medications in the “Antivirals” section in the “Antimicrobial” chapter of Open RN Nursing Pharmacology, 2e
Bacteria
Bacteria are microorganisms made of a single cell. They are very diverse, have a variety of shapes and features, and have the ability to live in any environment, including your body. However, not all bacteria cause infections. Those that cause infection are called pathogenic bacteria. See Figure 9.2[5] for an image of a bacterium called Escherichia coli (E. coli).
A client is susceptible to bacterial infections when their immune system is compromised by chronic diseases or certain types of medications. Antibiotics are used to treat bacterial infections. However, some strains of bacteria have become resistant to antibiotics, making them difficult to treat. For example, infections caused by methicillin-resistant Staphylococcus Aureus (MRSA) are resistant to many types of antibiotics and have the capability of producing severe and life-threatening infections. MRSA infections usually require IV antibiotics and may require treatment for long periods of time.[6]
Read additional information about antibiotics in the “Antimicrobials” chapter of Open RN Nursing Pharmacology, 2e.
Fungi
There are millions of different fungal species on Earth. Fungi can be found everywhere in the environment, including indoors, outdoors, and on human skin, but only about 300 species cause infection when they overgrow. Candida albicans is a type of fungus that can cause oral thrush and vaginal yeast i