L4 nature & properties of microorganisms

Question 1

what are the 4 infectious agents?

Answer 1

( smallest ) prions > viruses > prokaryotes > eukaryotes

Question 2

what is a prion

Answer 2

misfolded protein with ability to transmit shape onto normal proteins. resistant to disinfectants and heat so extremely difficult to inactivate.

Question 3

what is the mechanism of action for prions

Answer 3

• mutant prion with no DNA/RNA involved
• induces chain reaction of misfolded further host proteins
• degeneration of function

Question 4

what diseases are caused by prions?

Answer 4

• Creutzfeldt-Jakob Disease (CJD)
• Variant Creutzfeldt-Jakob Disease (vCJD)
• Bovine spongiform encephalopathy BSE (mad cow disease)

Question 5

BSE or mad cow disease is …

Answer 5

a progressive neurological disorder of cattle that results from infection by a prion. transmission via eating contaminated meat.

Question 6

Creutzfeld Jakob disease profile:

Answer 6

always fatal, no treatment, familial carrier, transmission orally, via blood, operative tissues

Question 7

what is a virus

Answer 7

protein capsid surrounding nucleic acid (DNA/RNA), it uses host cell machinery to replicate

Question 8

what are some viral effects on host cells?

Answer 8

degeneration, cell lysis, cell fusion to form larger cells, increased cell proliferation, malignant transformation(carcinogenic) latent/inactive infection e.g ‘cold sores’ or shingles

Question 9

Varicella zoster virus VSV profile:

Answer 9

dsDNA
causes chicken pox and shingles
lies dormant/latent in dorsal root ganglion

Question 10

Ebola profile mechanism and characteristics:

Answer 10

• ssRNA genome (-ve)
• natural source is in animals eg bats
• disease characterised by blood in vomit & stool, multi-organ dysfunction and death
• MECHANISM: attacks endothelial cells, phagocytes + hepatocytes
  -TREATMENT: Novel vaccine promising option + infection control is key!!

Question 11

Zika virus profile

Answer 11

causes microencephaly in neonates
results in severe neuro disorders (Guillain Barre) -> paralysis and death
infection via mosquitos bite and body fluids
diagnosis : blood test
treatment is pain relief , rest + hydration

Question 12

What are some types of bacteria? (3)

Answer 12

Obligate pathogens (always infectious e.g salmonella typhi)

Opportunistic pathogens (only in some settings e.g pseudomonas, anaerobes can infect open deep wounds)

Commensals - never pathogenic to humans e.g good microbiome gut bacteria that helps to digest food

Question 13

bacteria shapes

Answer 13

cocci round
bacili rod shape
others e.g comma shaped vibrio
helices: helicobacter

Question 14

what is bacteria structure

Answer 14

prokaryotes so NO: nucleus, mitochondria, ER, golgi

YES: cell wall, flagellae, fimbriae

Question 15

classification of bacteria is based on nucleic acid sequences mainly but ALSO Gram staining:

Answer 15

Gram negative = PINK stain
- double cell membrane with thin pepidoglycan in between E.G Ecoli, Klebsiella
Gram positive = PURPLE stain
- single membrane surrounded by thick peptidoglycan layer E.G Staphylococci, Streptococci

Question 16

how does bacteria cause disease?

Answer 16

Varies enormously e.g. Some invade cells
Disease (pathology) a function of:
Bacterial activity e.g. production of toxins, direct tissue damage
Host activity: The body’s Immune response to the presence of bacteria can cause damage itself.

Question 17

what products of bacteria cause disease?

Answer 17

Some bacterial products are designed to damage the host:
Toxins
Some are immunogenic and result in damage indirectly:
Bacterial lipopolysaccharides
Flagella

Question 18

fungi important features:

Answer 18

can be single or multicellular
eukaryotic
chitin cell wall
can grow hyphae(cylinder tubes that connect up to form mycelium)
can also produce bodies and spores