4th exam part 4

Infectious Disease

• Ants do not get sick because they have "little anty bodies". This is a joke.
• Innate immunity is the first line of defense against pathogens.
• Adaptive immunity is a more complex response, involving T cells and B cells.
• B-cell activation, antibody production against extracellular pathogens, and immune memory are parts of the humoral response.
• Cellular response includes cytotoxic T-cell activation, migration, and immune memory.
• Antibodies bind to antigens to neutralize, agglutinate or precipitate them. This inactivates antigens and enhances phagocytosis.
• Natural immunity is acquired through normal life experiences.
• Active immunity occurs when a person's immune system develops its own response to a microbe.
• Passive immunity occurs when one person receives preformed immunity made by another person.
• Artificial immunity is purposefully acquired through medical procedures (also called immunization).
• Host-microbe interactions involve colonization of the host with microorganisms. Infection does not always lead to noticeable adverse effects. Communicable diseases spread from host to host.
• Beneficial microbes are a part of normal flora living in and on the body, like those found in the gut (500 to 1000 different species).
• Harmful microbes are pathogenic microbes that cause disease when the body's defenses are down, also called opportunistic pathogens.
• Pathogenicity is the ability to cause disease which can be possessed by true pathogens or opportunistic pathogens.
• Virulence factors include capsules and cell wall components that help bacteria penetrate or evade host defenses, enzymes, siderophores, and antigenic variation.
• Damage to host cells, direct damage, toxins (exotoxins and endotoxins), and lysogenic conversion are also considered virulence factors.
• Virulence is a quantitative term referring to a pathogen's disease-causing ability.
• Highly virulent organisms have a high degree of pathogenicity and are more likely to cause disease.
• Biotic factors that lead to increased virulence include morphological characteristics, metabolic pathways, toxins, and enzymes.
• Infectious dose is the number of organisms required to establish infection. Diseases with a small infectious dose spread more easily than those requiring large numbers.
• ID₅₀ is the infectious dose for 50% of the test population.
• LD₅₀ is the lethal dose (of a toxin) for 50% of the test population.
• Smaller LD or ID means a more toxic or virulent organism.
• Portal of entry includes mucous membranes, respiratory tract, gastrointestinal tract, genitourinary tract, conjunctiva, skin, and parenteral route. Infection can occur in several ways in the same way that pathogens leave the body.
• Adherence factors involve binding by adhesions/ligands to receptors on host cells (glyco- or lipoproteins). Those include glycocalyx, fimbriae, and M protein.
• Exoenzymes/Proteins are enzymes or proteins secreted by bacteria, used for penetration and degradation of host defense proteins (Antibodies, complement, Cytokines).
• Toxins are substances that contribute to pathogenicity. Toxigenicity is the ability to produce a toxin. Toxemia is the presence of toxin in the host's blood. Toxoid is an inactivated toxin used in a vaccine. Antitoxin is antibodies against a specific toxin.
• Endotoxins are found in cell walls or cells, released after death. Exotoxins are secreted by the organism and are highly toxic.
• Metabolic pathways are degradation of antibiotics (beta-lactamases), export pumps for antimicrobials, and glycogen degradation.