Chapter 21 - Bacterial Pathogenicity

Question 1

pathogen

Answer 1

a microbe capable of causing disease

Question 2

host

Answer 2

organism being infected

Question 3

pathogenicity

Answer 3

ability to cause disease - pathogens very in their ability

Question 4

opportunistic pathogen

Answer 4

a microbe that typically infects a compromised host - such as by weakened immune system or breach to body’s natural defenses

Question 5

virulence

Answer 5

measurement of pathogenicity - highly virulent more likely to cause disease

Question 6

Host-pathogen interaction

Answer 6

always changing, and the virulence of a pathogen is important, but so is the number of microbes that gained entry into the host, location, and overall health of the host.

Question 7

reservoir

Answer 7

natural site of home for a pathogen - can be animate or inanimate

Question 8

carriers

Answer 8

assist in spreading pathogen from reservoir to a host and then to another infected host - show no signs of the disease

Question 9

zoonosis

Answer 9

disease that primary occurs w/in animal pops but can be spread to humans

Question 10

nosocomial infection

Answer 10

hospital-acquired infection

Question 11

transmission

Answer 11

mechanism by which a pathogen is picked up by a host

Question 12

direct contact

Answer 12

host-to-host contact - kissing, fucking, where one person is coming into contact w/ another fluids.

Question 13

Droplet transmission

Answer 13

considered to be direct contact - transmission by respiratory droplets. Droplets are sneezed or coughed by infected and inhaled by a host nearby - not long distances, don’t live long

Question 14

Indirect contact

Answer 14

transfer through an intermediary such as object or person. example shared toy or doorknob. Also health care worker - 1 pt to another pt

Question 15

fomite

Answer 15

inanimate object w/ a pathogen on it

Question 16

Airborne Transmission

Answer 16

pathogens that are small particles or droplets in the environment and remain infectious over time and distance - fungal sports during dust storm

Question 17

fecal-oral transmission

Answer 17

infected host shedding pathogen in their feces that then contaminates food/water and consumed by next host

Question 18

vectorborne transmission

Answer 18

when mosquitoes, flies, ticks, are involved. Can be when the vectors picks up agents on external body. However typically is when infectious agent bites and infected host and then spreads it w/ bite on uninfected host.

Question 19

Virulence Factors

Answer 19

characteristics that contribute to the capabilities of a bacterium to be virulent - such as physical or chemical structures

Question 20

pathogenicity islands

Answer 20

genes that code for virulence factors - commonly found clustered on pathogens chromosome or plasmid DNA - facilitate sharing of virulence factors between bacteria due to HGT - leads to development of new pathogens over time

Question 21

how can one distinguish pathogenicity island?

Answer 21

look for G+C content that differs from the rest of the genome - also presence of insertion like sequences flanking the gene cluster

Question 22

quorum sensing

Answer 22

often controls genes for virulence factors - ensures gene activation when pathogen population is @ optimal density

Question 23

why is quorum sensing important

Answer 23

triggering genes too soon could alert host’s immune system and cut bacterial infection short

Question 24

Adherence

Answer 24

adhesion to host cells as well as resistance from phagocytosis - can involve polysaccharide layers made by bacteria (capsule of slime layer) as well as pilus or flagellum

Question 25

Colonization

Answer 25

After adherence to a surface, a colony is built by increasing in number and utilizing resources available. Important for pathogen survival

Question 26

Invasion

Answer 26

ability of a pathogen to spread to other locations in the host - when signs/symptoms of a disease will occur

Question 27

Invasion - what happens during this?

Answer 27

bacterial pathogens produce chemicals (enzymes) that effect host’s cells and tissues.

Question 28

collagenase.

Answer 28

Enzyme released during invasion - breaks down collagen found in connective tissue

Question 29

leukocidins

Answer 29

enzyme released during invasion - destroy hosts WBC’s and decrease resistance

Question 30

Hemolysins

Answer 30

enzyme released during invasion - lyse host’s RBC’s, releasing iron - growth limiting factor for bacteria

Question 31

bacteremia

Answer 31

bacteria in the blood stream

Question 32

septicemia

Answer 32

massive, systemic infection (sepsis) and can result in septic shock and death

Question 33

Toxins

Answer 33

very specific virulence factor produced by some bacterial pathogens - poisonous to the host

Question 34

Toxigenicity

Answer 34

organism’s ability to make toxins

Question 35

exotoxin

Answer 35

heat-sensitive soluble proteins released into environment by living organism - associated w/ specific diseases w/ toxin genes often carried on plasmids or by prophages

Question 36

Type I exotoxin

Answer 36

cell surface-active: bind to cell receptors and stimulate cell response. ex. superantigen

Question 37

superantigen

Answer 37

type 1 exotoxin - stimulates host T Cells that then produce excessive amount of the signaling molecule cytokine leading to increased inflammation and tissue damage

Question 38

Type II exotoxin

Answer 38

membrane damaging: exert their effect on cell membrane, often by forming pores. Can lead to lysis as cytoplasmic contents rush out and H2O rushes in, results in disruption of osmotic balance.

Question 39

Type III exotoxin

Answer 39

intracellular: gain access and stimulate reaction w/in target cell. ex. AB-Toxin

Question 40

AB-Toxin

Answer 40

Type III exotoxin - composed of 2 units (A + B). B is binding portion of toxin, recognizes and binds to correct cell type. A contains enzymatic activity and is delivered to cell by the B Portion. A portion then acts on the host cell leading to decreased cell function or death. example of AB is tetanus toxin. each AB-toxin is associated w/ different disease.

Question 41

AB-Toxin on Neuron

Answer 41

A subunit will cleave cellular synaptobreven, resulting in decrease in neurotransmitter release. Results in spastic paralysis of the host.

Question 42

endotoxin

Answer 42

made by gram negative bacteria as a component of outer membrane. Outer membrane contains LPS and a toxic component (lipid a). Lipid A is heat stable and only released when cell is lysed. - effect is same regardless: fever, diarrhea, weakness, and blood coagulation. Can result in endotoxin shock.