Lecture 1

Question 1

Microbes have to adapt to survive and cause infection

Answer 1

Removing ability to adapt eliminates infectivity

Question 2

Pholgeny

Answer 2

Bacteria and archaea are prokaryotes
Eukarya are eukaryotes
There are no archaea that cause infection in humans

Question 3

Prokaryotes and eukaryotes

Answer 3

Eukaryotes: nucleus, organelles, complex processes, approx 8um dia

Prokaryotes: not as complex, no organelles, approx 1-3um

Question 4

Gram + and -

Answer 4

\+ = large peptidoglycan, cytoplasmic membrane. PURPLE gram stain
- = LPS, outer membrane. periplasmic space (thin peptidoglycan), cytoplasmic membrane. PINK gram stain

LPS toxic, G-ve cells difficult to treat with antibiotics as they cannot cross the double membrane (permeability)

Question 5

LPS (G-)

Answer 5

structure of LPS varies depending on environmental stimuli (e.g. antibiotics)
changes behaviour, charge, inflammatory properties of the LPS
Lipid A (outer membrane), core polysaccharide, O specific polysaccharide (inner membrane)
Repeating units of sugars, highly inflammatory

Question 6

Morphology

Answer 6

coccus, rod, spirillum, spirochete, filamentous, stalk+hypha

Question 7

Pathogenicity

Answer 7

the ability of a pathogen to cause disease within a given host
pathogenicity is an absolute term, not quantitative
opportunistic pathogens only cause disease in the absence of normal host resistance

Question 8

Virulence

Answer 8

quantitative measure of pathogenicity - the relative ability of a pathogen to cause disease
- cell number that elicits disease in a host in a given time period
- duration of host survival post infection
- severity of symptoms
LD50 and ID50

Question 9

Virulence factors examples

Answer 9

• secreted products
• surface proteins
• iron aquisition proteins
• flagella
• adhesins
• LPS
• endotoxins
• capsule
• pili
• secretion systems