Microbiology: Normal Flora, Disease Progression, and Immune System

A comprehensive set of vocabulary flashcards covering microbial relationships, disease progression, virulence factors, and the components of the human immune system.

Normal flora (microbiota)

Microbes that live on or in the body, usually do not cause disease, and participate in mutualistic or commensal relationships with the host.

Mutualism

A relationship between two organisms where both organisms benefit.

Commensalism

A relationship between two organisms where one benefits and the other is unaffected.

Microbial Antagonism

A process where normal flora help prevent pathogen growth by occupying attachment sites, competing for nutrients, and preventing pathogen colonization.

Skin (Normal Flora)

Body site populated by microbes such as Staphylococcus, Micrococcus, Corynebacterium, Propionibacterium, and Streptococcus.

Oral Cavity (Normal Flora)

Body site populated by microbes such as Streptococcus, Neisseria, Lactobacillus, Actinomyces, and Candida.

Large Intestine (Normal Flora)

Body site populated by microbes such as Bacteroides, Clostridium, Lactobacillus, Escherichia coli, and Enterobacter.

Genitourinary Tract (Normal Flora)

Body site populated by microbes such as Lactobacillus, Streptococcus, Corynebacterium, Escherichia, Gardnerella, and Candida.

Sterile Sites

Areas of the body that do not contain normal flora, including the brain, blood, kidneys, lungs, bones, cerebrospinal fluid, and internal organs.

Portal of Entry

The route through which a pathogen enters the body, such as the skin, respiratory tract, GI tract, urogenital tract, or transplacental route.

Infectious Dose (ID)

The minimum number of organisms needed to establish an infection; a lower infectious dose indicates greater virulence.

Adhesion

The process by which a pathogen attaches to host tissues using structures like fimbriae, flagella, capsules, slime layers, viral receptors, or hooks/suckers.

Incubation Period

The stage of disease where the pathogen is multiplying but the host has no symptoms yet.

Prodromal Stage

The stage of disease characterized by vague symptoms such as malaise and general discomfort.

Period of Invasion

The stage of disease where the pathogen is established and specific symptoms appear.

Convalescent Stage

The stage of disease during which the host is recovering and symptoms decline.

Pathogen

A disease-causing microorganism.

Pathogenicity

The ability of a microorganism to cause disease.

Virulence

The degree of pathogenicity of a microorganism.

Opportunistic Pathogen

A microbe that causes disease when host defenses are weakened or when it enters an abnormal location.

Fomite

An inanimate object, such as a door handle, phone, or towel, that spreads disease.

Mechanical Vector

A living organism, such as a fly, that only carries a pathogen from one place to another.

Biological Vector

A living organism, such as a mosquito spreading malaria, that participates in the pathogen's life cycle.

Reservoir

The natural habitat of a pathogen.

Carrier

A person who harbors and spreads a pathogen; types include asymptomatic, incubation, convalescent, chronic, and passive.

Endemic

An infectious disease that is constantly present in a population.

Epidemic

An occurrence of a disease at a rate higher than expected.

Pandemic

An epidemic that has spread worldwide.

Sporadic

A disease that occurs occasionally at irregular intervals.

Bacteremia

The presence of small numbers of bacteria in the blood.

Septicemia

A condition where microbes are actively multiplying in the blood.

Sign

Objective evidence of disease, such as a fever.

Symptom

Subjective evidence of disease, such as pain.

Leukocidins

Anti-phagocytic factors that kill white blood cells.

Hyaluronidase

An extracellular enzyme known as 'spreading factor' that breaks down the cellular 'cement' or connective tissue.

Exotoxins

Potent, heat-labile proteins secreted from live bacteria that target specific cells and can be converted into toxoids.

Endotoxins

Heat-stable lipopolysaccharides (LPS) released during bacterial lysis, specific to Gram-negative bacteria, and capable of producing fever and shock.

First Line of Defense

Physical and chemical barriers of the immune system, such as skin, mucous membranes, stomach acid, and lysozyme.

Second Line of Defense

Non-specific immune responses including inflammation, fever, phagocytosis, interferon, and complement.

Third Line of Defense

Specific immune responses involving B cells, T cells, antibodies, and memory cells.

Serum

The liquid portion of blood (plasma) without clotting factors.

Neutrophils

General-purpose phagocytic granulocytes that act as early defenders.

Eosinophils

Granulocytes primarily involved in attacking parasites and mediating allergic responses.

Basophils

Granulocytes that recruit inflammatory cells to the site of infection.

Monocytes

Agranulocytes that leave the blood to become macrophages.

Macrophages

Professional phagocytes that develop from monocytes and destroy pathogens.

Dendritic Cells

Cells that help activate adaptive (third line) immunity.

PRRs

Pathogen Recognition Receptors used by the immune system to recognize microbes.

Diapedesis

The movement of white blood cells out of blood vessels and into tissues.

Chemotaxis

The movement of cells toward chemical signals released at the site of injury or infection.

Pyrogens

Chemicals that cause fever; can be exogenous (from pathogens like LPS) or endogenous (produced by immune cells).