Micro CH 10: Part 1

Dysbiosis

microbiota disruption

Tropism

preference of a pathogen for a specific host (and even a specific tissue within the host)

Pathogenicity

ability of a microbe to cause disease

Virulence

describes the degree or extent of a disease that a pathogen causes

Virulence factors

mechanisms pathogens use to overcome our defenses

Pathogens

disease-causing microbes - Viruses, prions, bacteria, protozoans, helminths, and fungi

R0

measure of a pathogen’s transmissibility or contagiousness

Re

effective reproduction number

Attenuated

pathogen is still infectious, but weakened

Infectious dose-50 (ID50)

Number of cells or virions needed to establish an infection in 50% of exposed hosts

Lethal dose-50 (LD50)

Amount of toxin needed to kill 50% of affected hosts that are not treated

Toxins

molecules that generate a range of adverse host effects such as tissue damage and suppressed immune response

Toxigenic

microbes that make toxins

Toxemia

toxins in the bloodstream

Endotoxins

Gram-negative bacteria have an outer membrane rich in lipopolysaccharide (LPS)

Endotoxemia

endotoxin in the bloodstream

Exotoxins

Toxic, soluble proteins

Affect a wide range of cells

Made by both Gram-positive and Gram-negative bacteria

Neurotoxins

affect the nervous system

Enterotoxins

target the GI tract

Hepatotoxins

affect the liver

Nephrotoxins

damage the kidneys

superantigens

Also called pyrogens (cause fevers)- Overstimulate the immune system to cause

massive inflammation that harms the host

Type I exotoxins

Membrane-acting extracellular toxins - Bind to target via receptors on the surface

Type II exotoxins

Membrane-damaging toxins - Disrupt the host cell plasma membrane

hemolysins

hemolytic toxins that lyse red and white blood cells

Type III exotoxins

intracellular toxins - Bind to a receptor and enter the cell

Portal of entry

any site that a pathogen uses to enter the host

Integumentary system

Based on overall weight and surface area is the largest body system (skin, hair, nails, and

associated glands) - Blocks most microbes

Respiratory Tract

Coughing and sneezing suspends pathogens in the air as respiratory droplets

Infectious agents stirred up from dust or soil

Gastrointestinal (GI) Tract

Frequently have a fecal–oral transmission

Invade the mucosal surfaces

Urogenital Tract

sexually transmitted - mucosal lining of the vagina or cervix in women or the urethra in men or invade through the skin of the genitalia

urinary tract infections - invade the urethra in men and women

Transplacental

vertical transmission - cross the placenta to infect the fetus

Adhesins

virulence factors used to stick to host cells in a specific or nonspecific manner

Invasions

Allow pathogens to invade host tissues

biofilms

60–80% of human infections originate here - on almost every surface

Motility

Important invasion strategy that helps a pathogen spread

Transferrin

binds to iron and shuttles it to tissues

Lipases

break down lipids

Proteases

break down proteins

extracellular enzymes

Break down nutrients in the local environment - Allow pathogens to scavenge nutrients as they damage host tissues

Cytocidal

kill the cell

Noncytocidal

damage the cell

Intracellular pathogens

all viruses, many protozoans, and some bacterial pathogens - Spend a majority of their time inside host cells

Latency

Ability of a pathogen to quietly exist inside a host - Usually causes persistent or recurrent disease

Antigenic masking

Upon entering the host, the pathogen may conceal antigenic features - Coats itself with host molecules

Antigenic mimicry

Emulating host molecules - Capsules can resemble host carbohydrates

Antigenic variation

Periodically altering the surface molecules -Prevents a rapid immune response

Interference of phagocytosis

normally engulf and then destroy pathogens with hydrolytic enzymes

Immune suppression

targeting immune system cells, Making proteases that break down host antibodies, Interfering with transcription of immune system, Interfering with the molecular signaling