Chapter 14

Question 1

pathogenicity

Answer 1

ability to cause disease

Question 2

pathogenesis

Answer 2

steps or mechanisms involved in the development of a disease

Question 3

infectious disease

Answer 3

• a disease caused by a microbe (a pathogen)

- infection is a common synonym

Question 4

infection

Answer 4

• colonization by a pathogen

- the pathogen may or may not cause disease

Question 5

why infections don’t always occur (8)

Answer 5

• microbe in a site where it can’t multiply
• pathogen is unable to attach to receptor sites
• antibacterial factors may be present at site
• indigenous microbiota may inhibit growth
• indigenous microbiota may produce antimicrobial factors to destroy pathogen
• nutrition and health status may result in poor pathogen outcome
• person may be immune to pathogen
• phagocytes may be present in blood

Question 6

phases in course of disease

Answer 6

• exposure to pathogen
  1) incubation period
  2) prodromal period (feel bad but not sick yet)
  3) period of illness
  4) convalescent period (or disability or death)

Question 7

localized infection

Answer 7

• disease may remain localized or spread

- pimples, boils, abscesses

Question 8

systemic (generalized) infection

Answer 8

• when the infection spreads throughout the whole body

- TB

Question 9

acute disease

Answer 9

• rapid onset and rapid recovery

- measles, mumps, influenza

Question 10

chronic disease

Answer 10

• slow onset and lasts a long time

- TB, leprosy, syphilis

Question 11

subacute disease

Answer 11

• comes on more suddenly than chronic but less suddenly than acute
• bacterial endocarditis

Question 12

symptom

Answer 12

• evidence of disease experienced by the pt

- aches, pain, nausea, dizzy, blurred vision

Question 13

signs

Answer 13

• objective evidence of a disease

- abnormal heart sounds, high pulse, lab results

Question 14

symptomatic disease

Answer 14

pt experienced symptoms

Question 15

asymptomatic disease

Answer 15

pt does not experience symptoms

Question 16

latent infection

Answer 16

• go from being symptomatic to asymptomatic to symptomatic
• not getting reinfected but goes into dormant stage
• syphilis, herpes, shingles

Question 17

stages of syphilis

Answer 17

1) primary - 3 wks after exposure, painless chancre
2) secondary - 4-6 wks after exposure, rash develops but heals after 12 months
3) latent - no symptoms, may last lifetime
4) tertiary - 5-20 yrs after exposure, CNS and cardio symptoms (sometimes death)

Question 18

primary infection

Answer 18

first disease

Question 19

secondary infection

Answer 19

second disease

Question 20

example of primary and secondary infection

Answer 20

• viral respiratory infection damages epithelial cells
• epithelial cells unable to clear opportunistic bacteria
• opportunistic bacteria cause secondary infection of bacterial pneumonia

Question 21

steps in pathogenesis of infectious diseases

Answer 21

1) entry of pathogen into body
2) attachment of pathogen to tissues
3) multiplication of pathogen
4) invasion or spread of pathogen
5) evasion of host defences
6) damage to host tissues

Question 22

virulence

Answer 22

used to express the degree of pathogenicity

Question 23

virulent vs avirulent

Answer 23

• virulent can cause disease

- avirulent can’t cause disease

Question 24

virulence examples

Answer 24

• toxigenic C diphtheria can cause diphtheria (virulent), nontoxigenic cannot (avirulent)
• 10 shigella cells to cause shingellosis but 100-1000 salmonella cells to cause salmonellosis, shigella more virulent than salmonella
• some Streptococcus progenies more virulent than others
• some staphylococcus aureus more virulent than othres

Question 25

virulence factors

Answer 25

- attributes than enable pathogens to attach, escape destruction, or cause disease - they are phenotypic characteristics - adhesins (ligands) and pili

Question 26

adhesins (ligands) virulence factor

Answer 26

- molecules on surface of bacteria that enable pathogens to be recognize and bind to host cell receptors

Question 27

pili viruence factor

Answer 27

- enable bacteria to attach to surfaces like tissues

Question 28

obligate intracellular pathogens

Answer 28

- pathogens that must live within host cells in order to survive and multiply - rickettsia and chlamydia

Question 29

intraleukocytic pathogens

Answer 29

- live within WBCs cause diseases like ehrlichiosis and anaplasmosis

Question 30

intraerythrocytic pathogens

Answer 30

- live within RBCs | - plasmodium app that cause malaria and babes spp that cause babesions

Question 31

facultative intracellular pathogens

Answer 31

capable of intracellular and extracellular existence

Question 32

intracellular survival mechanisms

Answer 32

- cell wall composition that resist digestions (M. TB) - prevention of fusion of lysosomes with phagosomes - production of phospholipase that destroy phagosome membrane - other unknown mechanisms

Question 33

capsules

Answer 33

- virulence factor | - streptococcus pneumonias, klebsiella pneumonias, haemophilus influenza, neisseria meningitidis

Question 34

flagella

Answer 34

- virulence factor - enable bacteria to invade aqueous areas of body - may also help to escape phagocytes

Question 35

major mechanisms by which pathogens cause disease

Answer 35

exoenzymes or toxins they produce

Question 36

exoenzymes (7)

Answer 36

- necrotizing enzymes that cause necrosis - coagulase that cause clotting - kinases that break up clots - hyaluronidase that breaks down hypotonic acid for movement - collagenase that breaks down collagen - hemolysins that break down host RBC, alpha has green halo beta has white halo - lecithinase that breaks down phospholipid cell membrane causing tissue damage

Question 37

toxins

Answer 37

- poisonous substances released by pathogens | - endotoxins and exotoxins

Question 38

endotoxins

Answer 38

- part of cell wall of gram - bacteria | - can cause adverse physiologic effects like fever and shock

Question 39

exotoxins

Answer 39

- poisonous proteins secreted by pathogens - neurotoxins, enterotoxins (GI), exfoliative toxin (scalid skin syndrome), erythrogenic toxin (scarlet fever) and leukocidins (destroy WBC)

Question 40

antigenic variation

Answer 40

- changing surface antigens

Question 41

camouflage and molecular mimicry

Answer 41

- conceal their foreign nature by coating themselves with host proteins

Question 42

destruction of antibodies

Answer 42

- produce IgA protease that destroys some of hosts antibodies

Question 43

mechanisms by which pathogens escape immune response

Answer 43

- antigenic variation - camouflage and mimicry - destruction of antibodies