Chapter 25: Host-Pathogen Interactions

Question 1

opportunistic pathogens

Answer 1

many elements of normal flora act as opportunistic pathogens in susceptible hosts (heart disease, immunosuppression, radiation therapy, chemotherapy, MRSA)

Question 1

obligate pathogens

Answer 1

never part of normal flora, always cause disease, usually require host for multiplication (HIV, hansen’s disease/leprosy)

Question 2

mucous membrane barrier

Answer 2

first line of defense against pathogens
secrets glycoproteins (retain water)
lysozymes
antibodies
averts infection by flushing: sneezing, swallowing, erosion etc.

Question 3

virulence

Answer 3

relative ability to cause disease

Question 4

virulence factors

Answer 4

structures or molecules of an organism that increase its pathogenicity

Question 5

examples of virulence factors

Answer 5

flagella- motility, attachment
frimbriae- attachment
capsule- concealment, attachment
adhesions- receptors of pathogen surface, glycoproteins, lipoproteins
exotoxins
endotoxins

Question 6

endotoxin

Answer 6

structural part of outer membrane
secreted as part of normal physiological activity during membrane vesicle trafficking while also excreting other virulence factors and proteins
set free passively when cells die or disintegrated

Question 7

lipopolysaccharide (lps) layer

Answer 7

replaces most of phospholipids in outer half of outer membrane
lipid a- host receptor recognition, differing chemistry among species
lps/lipid a structure determines immunogenicity
can cause inflammatory reactions
disregulation of: immune system, clotting cascade, blood pressure regulation
results in: fever, wbc count, hemorrhaging/clotting/ lowered bp, shock, death

Question 8

exotoxins

Answer 8

inhibits host cell function or kills host cells
proteins release from pathogen cells as it grows

Question 9

categories of exotoxins

Answer 9

cytolytic toxins, ab-toxins, superantigen toxins

Question 10

cytolytic toxins

Answer 10

work by degrading cytoplasmic membrane integrity causing cell lysis and death

Question 11

examples of cytolytic toxins

Answer 11

hemolysin: lyses RBCs
leukocidin: lyces WBCs
phospholipases: hydrolyze phospholipids into fatty acids

Question 12

diptheria ab-exotoxin

Answer 12

blockage of protein synthesis
causes thick covering in back of throat
leads to difficulty breathing, heart failure, paralysis, death

Question 13

neurological exotoxins

Answer 13

botulinum and tetanus

Question 14

clostridium tetani and botulinum

Answer 14

produce potent AB-exotoxins that affect nervous tissue
botulinum toxins most potent biological toxins known

Question 15

tetanus

Answer 15

opposite effect of botulinum
muscular rigidity/arrest in tension
rigid paralysis

Question 16

enterotoxin

Answer 16

ab-exotoxins whose activity affects small intestine
cause massive secretion of fluid into lumen, vomiting and diarrhea
cholera toxin in vibrio cholerae

Question 17

superantigens

Answer 17

cause overstimulation of immune sytstem
shock and death
due to localized infecion with systemic effects
can cause bacteremia or septicemia
causes non specific activation of t-cells resulting in polyclonal t-cell activation and massive cytokine release
fever, kidney disruption, liver etc.

Question 18

exo-enzymes as virulence factors

Answer 18

invasiveness requires a pathogen break down host tissues, often done with enzymes that attack host cells

Question 19

examples of exo-enzymes as virulence factors

Answer 19

enzymes that
break down tissue
manipulate clotting of fibrin

Question 20

measuring virulence

Answer 20

not how many factors, bu how aggressively an infection and disease is established
estimated from experimental studies of LD50

Question 21

highly virulent pathogens

Answer 21

show little difference in number of cells required to kill 100% of population

Question 22

compromised host

Answer 22

one or more resistance mechanisms are inactive:
genetic predisposition
permanent primary infection
temporary condition
medical procedures
predispose individuals to develop disease

Question 23

attenuation

Answer 23

decrease or loss of virulence
attenuated strains are valuable to clinical medicine, used as vaccines