Pathogens and Host

Question 1

organism must be found in all cases of the disease
able to be cultured outside the body for several generations
should reproduce the disease on inoculation

Answer 1

Koch Postulate

rem by postulate = inoculate in Petri dish

Question 2

Ability to become established

Answer 2

Infectivity

1. Infect and est 2. Then virulent (cause harmful effect once est)

Attachment - E. coli - P-fimbriae. receptor on uroepithelial cells
Acid resistance - Helicobacter pylori - Urease - Makes ammonia from urea

Question 3

Ability to cause harmful effects once established

Answer 3

Virulence

Virulence factors
Genetically determined microbial components
Invasiveness
Toxin 
Evasion of immune system
Specific to strains, not species

Question 4

Streptococcus pyogenes cause NIPPLES

Answer 4

Necrotising fasciitis and myositis
Impetigo
Pharyngitis
Pneumonia
Lymphangitis
Erysipelas and cellulitis
Scarlet fever/ Streptococcal TSS

Question 5

Streptococcus pyogenes virulence factors are SMASHED

Answer 5

Streptolysins 
M protein
Anti-C5a peptidase
Streptokinase (fibrinolysis)
Hyaluronidase and collagenase (CT Breakdown/ cellulitis)
Exotoxin
DNAses

Question 6

Produced only by Gram-negative bacteria
Integral part of cell wall
lipopolysaccharide (LPS ) - Lipid A nasty
Only one type of endotoxin

Answer 6

Endotoxin

Question 7

Produced by both Gram-positive and Gram-negative bacteria	
Released from cell	 
Protein
Many types of exotoxin based 
on structure and function

Answer 7

Exotoxin

Eg. Enterotoxin act on GI

Question 8

obligate anaerobe
Infection of dirty wounds
Toxin - Binds to nerve synapses, Inhibits release of inhibitory neurotransmitters
Death caused by respiratory paralysis
Treated by debridement, antibiotics and antitoxin

Answer 8

Clostridium tetani

Question 9

Colonises small intestine
Enterotoxin production
Increases cAMP levels
Inhibits uptake of Na+ and Cl- ions
Stimulates secretion of Cl- and HCO3- ions
Passive (massive) outflow of H2O
Causes death by dehydration
Treated by rehydration

Answer 9

Vibrio cholerae

Question 10

certain exotoxins of Strep pyogenes and Staph aureus
able to stimulate division of T cells in the absence of specific antigen
overwhelming cytokine production causes “toxic shock”

Answer 10

Superantigens

Question 11

What component of gram neg is endotoxin?

Answer 11

Lipid A of LPS