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IIH > Nature and Properties of Microorganisms > Flashcards

Nature and Properties of Microorganisms Flashcards

1
Q

Define prion.

A

A pathogenic protein that disrupts protein folding in an exponential chain reaction.

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2
Q

Give an example of a prion.

What disease is caused by this prion?

A
  • The normal PrPc protein (found in neural tissue and tonsils) can be converted into PrPsc, a prion.
  • PrPsc causes protein folding to form amyloid fibres, which aggregate and lay down deposits, causing Creutzfeldt-Jakob disease (CJD).
  • This is a form of spongiform encephalopathy.
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3
Q

List 3 methods by which Creutzfeldt-Jakob disease can be transmitted.

A

1 - Sporadic (mutation).

2 - Familial.

3 - Oral and blood transmission (for particular variants of CJD only).

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4
Q

Why are prions difficult to remove or inactivate?

A

Because they are resistant to disinfectant and heat treatment.

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5
Q

What causes mad cow disease?

A

A prion similar to the human prion causing Creutzfeldt-Jakob disease.

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6
Q

Give an example of a DNA virus.

A

Herpes simplex virus.

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7
Q

Give an example of an RNA virus.

A

Influenza.

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8
Q

What is the Baltimore scheme?

Why is it useful?

A
  • A system for categorising viruses on the basis of their genome and how it is replicated.
  • It is useful as it can predict the behaviour of members of the same group.
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9
Q

What is a tegument?

A

A cluster of proteins that lines the space between the envelope and nucleocapsid of all herpesviruses.

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10
Q

List 2 important proteins that are expressed on the surface of the influenza virus.

A

1 - Neuraminidase.

2 - Haemagglutinin.

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11
Q

What is the function of neuraminidase?

A

To enable the virus to be released from the host cell by cleaving glycoproteins.

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12
Q

What is the function of haemagglutinin?

A

To facilitate entry of the virus into host cells by fusing the membrane of the virus and the host cell.

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13
Q

List the stages of a generic viral life cycle.

A

1 - Attachment to host cell.

2 - Entry into host cell.

3 - Loss of envelope and release of viral nucleic acid.

4 - Replication of genome and protein production.

5 - Assembly of new virions.

6 - Release from cell.

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14
Q

What are the two major sites of antiviral drug action?

A

1 - Cell attachment.

2 - Intracellular replication.

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15
Q

What is the effect of cytomegalovirus on the host cell?

A

Causes morphological changes, resulting in lysis.

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16
Q

What is the effect of respiratory syncitial virus on the host cell?

A

Cell fusion, causing the formation of syncytia.

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17
Q

What is the effect of parvoviruses on the host cell?

A

Can induce malignancies.

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18
Q

Describe the morphological change that would arise with cytomegalovirus hepatitis.

A

Causes an ‘owl-eye effect’ inclusion body (an aggregate of proteins).

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19
Q

List 2 diseases that can be causes by varicella zoster virus.

A

1 - Chickenpox.

2 - Shingles.

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20
Q

List 2 viruses that cause latent infection.

A

1 - Herpes simplex virus.

2 - Varicella zoster virus.

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21
Q

To which family of viruses does ebola belong?

A

Filoviruses.

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22
Q

What type of genome does ebola have?

A

Single stranded RNA.

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23
Q

List the cells that are targeted by ebola.

A

1 - Endothelial cells.

2 - Mononuclear phagocytes.

3 - Hepatocytes.

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24
Q

Define ring vaccination.

A

A strategy to inhibit the spread of a disease by vaccinating only those who are most likely to be infected.

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25
Q

List 2 diseases caused by zika virus.

A

1 - Microcephaly (abnormally small head in neonates).

2 - Guillain-Barre syndrome.

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26
Q

How is zika virus transmitted?

A

1 - Via infected Aedes mosquito bites.

2 - Sexually transmitted.

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27
Q

How is zika virus treated?

A

Only by treating symptoms (mostly pain relief) rather than curative treatment.

28
Q

What is the name of bacteria that are never pathogenic?

A

Commensal bacteria.

29
Q

What is the name of bacteria that can be pathogenic, but are not always pathogenic?

A

Opportunistic bacteria.

30
Q

What is the name of bacteria that are always pathogenic?

A

Obligate bacteria.

31
Q

List 2 opportunistic bacteria.

A

1 - Pseudomonas.

2 - Most anaerobes, e.g. bacteroides fragilis.

32
Q

List 3 characteristics of prokaryotes.

A

1 - Lack a nucleus.

2 - Usually have a peptidoglycan cell wall.

3 - Can have protruding appendages.

33
Q

How do gram negative and gram positive bacteria stain in a gram stain test?

A
  • Gram positive stain purple.

- Gram negative stain pink.

34
Q

How is a gram stain test done?

A

1 - Application of crystal violet.

2 - Decolorization.

3 - Counterstaining, usually with safranin.

35
Q

List 4 gram negative bacteria.

A

1 - E. coli.

2 - Klebsiella.

3 - Pseudomonas species.

4 - Campylobacter species.

36
Q

List two gram positive bacteria.

A

1 - Staphylococcus species.

2 - Streptococcus species.

37
Q

Why do gram positive bacteria retain crystal violet dye whereas gram negative bacteria do not?

A
  • Gram positive cells have large cell walls lined exteriorly with peptidoglycan, which retains the dye.
  • Gram negative bacteria have two thin cell membranes with a thin peptidoglycan layer between them in the periplasmic space. They are therefore unable to retain the dye.
38
Q

What is lipoteichoic acid?

How does it cause pathogenic effects?

A
  • A surface-associated adhesion molecule in gram positive bacteria that spans the width of the peptidoglycan.
  • It is an immune irritant that causes septic shock.
39
Q

How do endotoxins (lipopolysaccharides) cause pathogenic effects?

Which bacteria use endotoxins?

A
  • Endotoxins are immunostimulators that cause sepsis.

- Gram negative bacteria use endotoxins.

40
Q

What is an O antigen?

What structural component of the O antigen gives a bacteria antigenic specificity?

A
  • Part of the lipopolysaccharide in the outer membrane of gram-negative bacteria.
  • It consists of oligosaccharide repeating units.
  • Antigenic specificity is conferred by the terminal repeat unit.
41
Q

List 3 drugs that target peptidoglycan.

A

1 - Penicillins.

2 - Cephalosporins.

3 - Vancomycin.

42
Q

What is the name of the major toxic lipopolysaccharide?

A

Lipid A.

43
Q

Define chemotaxis.

A

The process by which flagella move bacteria towards or away from a chemical attractant / repellent.

44
Q

What are fimbriae?

A

Pili.

45
Q

List 2 functions of fimbriae.

A

1 - Attachment to host cells.

2 - Transfer of plasmid DNA.

46
Q

Define opsonisation.

A

The molecular mechanism whereby a cell is modified (addition of opsonins) to have a stronger attraction to the cell surface receptors on phagocytes.

47
Q

Define exotoxin.

A

Protein toxins secreted by bacteria.

48
Q

What is a toxoid?

A

A chemically modified exotoxin that is no longer toxic, and can be used for vaccination.

49
Q

Give an example of a passive immune defence against exotoxins.

A

Antitoxin.

50
Q

What might cause cultures of Clostridium botulinum to form?

A

Poor canning.

51
Q

How does Clostridium botulinum cause pathogenic effects?

A

By producing a neurotoxin which causes paralysis.

52
Q

List 3 diseases caused by E. coli.

A

1 - Bacteraemia.

2 - UTIs.

3 - GI infections.

53
Q

List 2 diseases caused by Staphylococcus species.

A

1 - Bacteraemia.

2 - Wound infections.

54
Q

Which bacteria cause tuberculosis?

A

Mycobacterium tuberculosis.

55
Q

Give an example of a species of bacteria that causes respiratory tract infections.

A

Streptococcus pneumoniae.

56
Q

Which diseases does Campylobacter species cause?

A

GI infections.

57
Q

Which disease does Clostridium difficile cause?

A

Hospital acquired diarrhoea.

58
Q

Define sporulation.

What is the purpose of sporulation?

A
  • The formation of nearly dormant forms of bacteria.
  • In a limited number of bacteria, spores can preserve the genetic material of the bacteria when conditions are inhospitable.
59
Q

Which species of bacteria causes gonorrhea?

A

Neisseria gonorrhoeae.

60
Q

Which species of bacteria causes meningitis?

A

Neisseria meningitidis.

61
Q

In which kingdom is chitin present in the cell wall?

A

Fungi.

62
Q

What causes thrush (a vaginal yeast infection)?

A

Candida albicans (yeast).

63
Q

What is aspergillosis?

In which conditions does it arise?

A
  • A fungal infection caused by Aspergillus.

- Occurs in people with underlying illnesses, especially tuberculosis or COPD.

64
Q

What is the most common structure in which fungi grow?

A

Hyphae - cylindrical tubes which interconnect to form a mycelium.

65
Q

What type of disease is caused by Cryptococcus neoformans?

A

A respiratory yeast infection.

IIH (26 decks)

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