Key Terms
- acquired immunodeficiency syndrome (AIDS)
- latest and most severe stage of HIV, characterized by a low CD4 cell count and opportunistic infections
- adaptive immune response
- relatively slow but very specific and effective immune response controlled by lymphocytes
- antibiotic resistance
- increased ability of microorganisms to survive exposure to antibiotic medications
- antibiotic stewardship
- efforts to improve antibiotic prescribing strategies to more effectively treat infections and avoid the development of antibiotic resistance
- antigen
- molecule on the cell surface of a pathogen that is recognized as an invader by the immune system
- barrier defense
- skin, mucous membranes, and other components of the immune system that act instantaneously to prevent pathogenic invasion into body tissues
- bone marrow
- spongy material located inside the long bones and responsible for the production and maturation of blood cells
- Clostridioides difficile
- bacterium normally located in the intestines that can cause secondary inflammation of the colon, most often after taking antibiotics; also called C. diff
- colectomy
- removal of a portion of the colon
- contagious
- capable of spreading from one person to another
- coronavirus
- type of virus characterized by a lipid envelope surrounded by proteins that jut out like spikes
- deoxyribonucleic acid (DNA)
- self-replicating material that is present in all living organisms and the main constituent of chromosomes; the focus of genetics
- fecal transplant
- transfer of medically processed stool from a healthy donor into a colon infected by Clostridioides difficile bacteria
- fungus
- organism that belongs to the kingdom Fungi, characterized by eukaryotic cells that contain cell walls and vacuoles but not chloroplasts and that typically grow as tubular, thread-like structures called hyphae
- hepatitis
- condition characterized by inflammation of the liver; often a secondary result of a viral infection
- hepatocyte
- liver cell
- host
- organism that has been infected by another organism or virus
- human immunodeficiency virus (HIV)
- retrovirus characterized by the destruction of certain white blood cells, ultimately resulting in AIDS
- immune system
- complex collection of cells and organs that destroy or neutralize pathogens that would otherwise cause disease or death
- infectious disease
- caused by pathogenic microorganisms—agents such as bacteria, viruses, parasites, or fungi—that enter a human host, multiply, and cause infection that can spread via direct or indirect transmission
- innate immune response
- rapid but relatively nonspecific immune response
- leukocyte
- primary cell of the immune system that fight off pathogens to prevent infection; also called white blood cell
- liver cirrhosis
- damage to the liver that results in permanent scarring and fibrosis
- long COVID
- condition in which an individual has recovered from COVID-19 but continues to have symptoms and adverse effects for months after infection
- lymph
- interstitial fluid once it has entered the lymphatic system
- lymph node
- small, bean-shaped organs located along lymphatic vessels
- lymphatic system
- system of vessels, cells, and organs that carries excess fluids to the bloodstream and filter pathogens from the blood
- methicillin-resistant Staphylococcus aureus (MRSA)
- strain of Staphylococcus bacteria that has become resistant to many antibiotics
- opportunistic infection
- infection that arises from pathogens that would not normally cause infection in a healthy individual but occur when the immune system is not functioning optimally
- oral thrush
- infection caused by the fungus Candida albicans, which is found normally in the mouth but can become overgrown and pathological; also called oral candidiasis
- pathogen
- agent such as a bacterium, virus, parasite, or fungus that enters a human host, multiplies, and causes infection
- pathogenicity
- potential ability of a pathogen to cause disease in a susceptible host
- retrovirus
- virus composed of a ribonucleic acid strand that can be turned into DNA and permanently inserted into a healthy cell
- reverse transcriptase
- enzyme used to convert RNA into DNA
- ribonucleic acid (RNA)
- nucleic acid that is present in all living cells and that carries instructions from DNA for controlling protein synthesis
- secondary infection
- infection that arises after treatment for a different, primary infection; also called opportunistic infections
- spleen
- secondary lymphoid organ that filters pathogens from the blood and removes damaged blood cells
- thymus
- lymphatic organ whose main function is the production of a group of hormones that contribute to the development and differentiation of T lymphocytes
- vancomycin-resistant Enterococcus (VRE)
- strain of enterococci bacteria that has become resistant to treatment with the antibiotic vancomycin
- viral load
- amount of virus in the blood
- virulence
- severity of an infectious disease
- virus
- piece of genetic code, such as DNA or RNA, protected by a coating of protein and capable of self-directed movement and reproduction