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Flashcards in Pathogens and Host Deck (11):
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

Koch Postulate


rem by postulate = inoculate in Petri dish

2

Ability to become established

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

3

Ability to cause harmful effects once established

Virulence

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

4

Streptococcus pyogenes cause NIPPLES

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

5

Streptococcus pyogenes virulence factors are SMASHED

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

6

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

Endotoxin

7

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

Exotoxin

Eg. Enterotoxin act on GI

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

Clostridium tetani

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

Vibrio cholerae

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”

Superantigens

11

What component of gram neg is endotoxin?

Lipid A of LPS