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Yr 2 - Clinical Pathology > Immunology - Pathogens > Flashcards

Immunology - Pathogens Flashcards

1
Q

What are pathogens?

A

disease causing micro-organisms

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2
Q

What are the 4 groups of pathogens?

A
  1. Bacteria
  2. Viruses
  3. Fungi
  4. Parasites
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3
Q

What are bacteria?

A

Bacteria are prokaryotic micro-organisms

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4
Q

What are the 5 shapes of bacteria?

A
  1. Cocci
  2. Bacilli
  3. Spirilla
  4. Vibrios
  5. Spirochaete
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5
Q

Describe bacilli shape

A

Also known as rods, these are long and thin.

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6
Q

Describe cocci shape

A

These spherical micro-organisms are found grouped together, as staphylococci (clusters), streptococci (lines) or diplococci (paired).

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7
Q

Describe spirilla shape

A

Spiral-shaped bacteria, although these are less common.

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8
Q

Describe vibrios shape. What is an example?

A

Flagellated (tailed) organisms, a notable example of which is Vibrio cholerae, the causative organism of cholera.

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9
Q

Describe spirochaete shape. What is an example?

A

These are tightly coiled. An example of is Treponema pallidum, the causative organism of syphilis.

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10
Q

Which bacteria causes syphilis?

A

Treponema pallidum

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11
Q

What does gram-staining depend on?

A

Depends on the thickness of peptidoglycan present in the cell wall:

  • Gram-positive bacteria have a thick layer of peptidoglycan
  • Gram-negative have a thin layer.
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12
Q

Can Mycobacterium tuberculosis be stained?

A

No - gram-indeterminate.

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13
Q

Describe the results of gram-positive staining

A

Gram-positive organisms have a thick cell wall of peptidoglycan and so retain the crystal violet stain when washed with acetone/methanol. When safranin is added, it is retained but obscured by the crystal violet.

Therefore these cells stain purple.

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14
Q

Describe the results of gram-negative staining

A

Gram-negative organisms have an outer lipopolysaccharide layer. When acetone is added these lipids dissolve, exposing the relatively thin peptidoglycan membrane. Crystal violent/iodine complexes are able to exit which decolourises the cell.

Therefore when the red counterstain is added, gram-negative bacteria stain red

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15
Q

The final way of classifying bacteria is into aerobic and anaerobic, depending on their ability to survive with or without oxygen.

Anaerobic vs aerobic bacteria?

A

Aerobic bacteria can survive in the presence of oxygen, and obligate aerobes absolutely require oxygen to survive.

Anaerobic bacteria can survive without oxygen, and obligate anaerobes can only survive in an environment without oxygen.

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16
Q

What classification (gram stain and shape) is:

Staphylococcus aureus

Coagulase-negative staphylococcus

Beta-haemolytic streptococci

Streptococcus pneumoniae

Enterococcus faecalis

A

Gram-positive cocci

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17
Q

What classification (gram stain and shape) is:

Listeria monocytogenes

Bacillis anthracis

Bacillus cereus

A

Gram-positive bacilli

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18
Q

What classification (gram stain and shape) is:

Neisseria meningitidis

Neisseria gonorrhoeae

Moraxella catarrhalis

A

Gram-negative cocci

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19
Q

What classification (gram stain and shape) is:

Escherichia coli

Klebsiella pneumoniae

Salmonella typhi

Pseudomonas aeruginosa

Haemophilus influenzae

A

Gram-negative bacilli

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20
Q

Classification of Staphylococcus aureus?

A

Gram-positive cocci (clusters)

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21
Q

Classification of Neisseria meningitidis and Neisseria gonorrhoeae?

A

Gram-negative cocci

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22
Q

Classification of Listeria monocytogenes?

A

Gram-positive bacilli

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23
Q

Classification of E.coli?

A

Gram-negative bacilli

24
Q

Classification of Haemophilus influenzae?

A

Gram-negative bacilli

25
Q

What do viruses consist of?

A

A nucleic acid core, either DNA or RNA, which is either single or double stranded.

The virus is covered by a protein coat known as the “capsid”.

Some viruses also have an outer envelope.

26
Q

What are the two types of RNA found in a virus?

A

The RNA can be either ‘positive sense’ or ‘negative sense’ depending on the polarity of the nucleic acid

27
Q

Difference between positive and negative sense RNA?

A

Positive sense (5′-3′) RNA is directly translatable into viral proteins, while negative sense (3′ to 5′) is not.

Transcription must occur first with negative sense strands to create mRNA

28
Q

What does the cell capsid, or outer envelope if present, have attached to it?

A

Glycoproteins

29
Q

What do these glycoproteins on the outside of a virus bind to?

A

These bind to appropriate receptors on certain host cells

For example, glycoprotein 120 on the HIV virus binds to CD4 receptors on host T cells. This allows the virus to replicate and establish a viral infection.

30
Q

Are the herpes viruses enveloped or not?

A

Enveloped

31
Q

Describe structure (DNA or RNA, enveloped or not) of Hepatitis B

A

DNA, enveloped

32
Q

Describe structure (DNA or RNA, enveloped or not) of varicella zoster

A

DNA, enveloped (one of the herpes viruses)

33
Q

Describe structure (DNA or RNA, enveloped or not) of smallpox

A

DNA, enveloped

34
Q

Describe structure (DNA or RNA, enveloped or not) of Human Papillomavirus

A

DNA, non-enveloped

35
Q

Describe structure (DNA or RNA, enveloped or not) of Adenovirus

A

DNA, non-enveloped

36
Q

Describe structure (DNA or RNA, enveloped or not) of HIV

A

RNA, enveloped

37
Q

Describe structure (DNA or RNA, enveloped or not) of Influenza

A

RNA, enveloped

38
Q

Describe structure (DNA or RNA, enveloped or not) of Hep C

A

RNA, enveloped

39
Q

Describe structure (DNA or RNA, enveloped or not) of SARS-COV-2 (COVID)

A

RNA, enveloped

40
Q

Describe structure (DNA or RNA, enveloped or not) of Norovirus

A

RNA, non-enveloped

41
Q

Describe structure (DNA or RNA, enveloped or not) of Hep A

A

RNA, non-enveloped

42
Q

Process of viral replication:

A
  1. The virus is adsorbed onto the host cell membrane.
  2. Through the process of pinocytosis, the virus enters the cell in a vacuole.
  3. Uncoating occurs, where the outer protein coat is stripped to expose the genomic material.
  4. If an RNA virus, mRNA is generated directly. If a DNA virus or a negative sense RNA virus, transcription occurs to create mRNA.
  5. Viral mRNA hijacks host machinery to generate viral proteins. Viral nucleic acid is generated to facilitate further replication.
  6. The virion is assembled, which is an immature, inactive version of the virus. This contains the newly synthesised viral proteins and viral genomic material.
  7. The virion exits to infected another host cell, and the cycle repeats.
43
Q

What can fungi be subdivided into?

A
  1. Yeasts, which are single-celled

2. Moulds, which are multicellular.

44
Q

What are Candida albicans and Pneumocystis jirovecii examples of?

A

Yeasts

45
Q

What does Candida albicans cause?

A

Thrush infections

46
Q

What does Pneumocystis jirovecii cause?

A

respiratory infections in susceptible individuals.

47
Q

What can parasites be subdivided into?

A
  1. Protozoa (single-celled)

2. Helminths (worms)

48
Q

What are the 6 stages of viral replication?

A
  1. Attachment
  2. Entry
  3. Uncoating
  4. Replication
  5. Assembly
  6. Release
49
Q

Describe the attachment stage of viral replication

A

The virus becomes attached to the cell by specific cellular receptors which can be glycoproteins, phospholipids or glycolipids.

50
Q

Describe the entry stage of viral replication

A

Following attachment the virus can enter the cell, most commonly via receptor mediated endocytosis. This is the same process by which many hormones enter the cell.

51
Q

Describe the uncoating stage of viral replication

A

Once inside the host cell, the viral capsid must be uncoated to release the viral nucleic acid. Uncoating may be achieved by host or viral enzymes that will degrade the capsid.

52
Q

Describe the replication stage of viral replication

A

Once uncoated, viruses (DNA or RNA) replicate by switching the host machinery from cellular protein synthesis to viral synthesis and viral proteins are produced.

53
Q

Describe the assembly stage of viral replication

A

Newly synthesised viral proteins are post-transcriptionally modified and packaged into virions that can be released from the infected host cell to infect other cells.

54
Q

Describe the release stage of viral replication

A

Virions are released from the cell either by lysis or budding. In lysis, the infected cell dies and the virions are released. In budding, the virion takes some of the host cell’s membrane with it as it leaves – this normally does not kill the infected cell

55
Q

Which cell does HIV target?

Which glycoprotein does it use to do this?

A

CD4+ T helper cells

Using a protein called gp120 on its viral envelope to attach to the CD4 molecule of the T cell.

56
Q

Which enzyme is used for HIV to combine itself into the host cell’s genome?

A

Viral integrase

57
Q

What is viral integrase?

A

Retroviral integrase is an enzyme produced by a retrovirus that integrates—forms covalent links between—its DNA into that of the host cell it infects.

Yr 2 - Clinical Pathology (80 decks)

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