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Infections and Defence > Case Studies > Flashcards

Case Studies Flashcards

1
Q

Which bacteria can cause sore throats?

A

Streptococcus pyogenes

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2
Q

What type of bacteria is streptococcus pyogenes?

A

It is gram positive , so its cell wall is composed of peptidoglycan (M proteins). Does not have a polysaccharide layer.

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3
Q

List 6 virulence factors for streptococcus pyogenes

A

1) Surface M protein
2) Streptolysins
3) Hyaluronidase (inhibits phagocytosis)
4) Peptidoglycan
5) Teichoic acid

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4
Q

What will streptococcus pyogenes cause when put into blood agar?

A

It will cause beta haemolysis (clear halo around the colonies).
Alpha haemolysis is only partial haemolysis.

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5
Q

How is streptococcus pyogenes spread?

A

It is spread through person to person contact via droplets.

It can penetrate open wounds.

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6
Q

How does streptococcus pyogenes avoid opsonisation by phagocytes?

A

It has an anti-complement protein that binds to tot he M protein on the surface.
It has multiple antigenic M proteins.

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7
Q

What are 4 complications of streptococcus pyogenes that can occur?

A

1) Oedema
2) Hypertension
3) Haematuria
4) Proteinuria

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8
Q

How can acute infections of streptococcus pyogenes be treated?

A

Benzylpenicillin or clindamycin can be used.

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9
Q

How can streptococcus pyogenes cause toxic shock syndrome?

A

It may possess super antigens on its surface that can activate many cytokines through non specific activation of the immune system.

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10
Q

What can happen if streptococcus pyogenes enters the bloodstream from the oral cavity?

A

It can damage heart valves due to the cross reaction of the antibodies against the M protein in the bacteria with the host proteins in the heart valves.

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11
Q

How can clindamycin treat streptococcus pyogenes?

A

It stops protein synthesis of ribosomes, stops toxin production and penetrates soft tissue.

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12
Q

Describe the structure of Mycobacterium tuberculosis?

A

It has long chain fatty acids. Contains myolic acid which is a hydrophobic lipid shell that affects permeability.

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13
Q

What stain is used to diagnose mycobacterium tuberculosis?

A

The Ziehl Neelson stain.

It turns the bacteria bright red.

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14
Q

Name 3 drugs that can be used to treat tuberculosis

A

1) Isoniazid
2) Ethambutol
3) Pyrazinamide
4) Rifampicin

2 month induction, 4 month consolidation

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15
Q

Is tuberculosis aerobic or anaerobic?

A

It is a highly aerobic bacteria, therefore can be distributed as a secondary disease in the lungs.

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16
Q

What feature of tuberculosis makes it adaptable?

A

It can have variable gene expression therefore can carry out metabolic changes to aid its survival.

17
Q

How is tuberculosis spread?

A

It is spread by airborne droplets that are then phagocytosed by alveolar macrophages.
However this is unable to kill the bacteria as the bacteria is adapted to survive this.

18
Q

What percentage of people infected with TB are from low and middle income countries?

A

95%

19
Q

What is formed by the body in order to try and limit the spread of TB?

A

Granulomas are formed.
They are a collection of activated macrophages that surround areas of necrosis.
TNF alpha is released to recruit more macrophages.
Forms small areas of inflammation.

20
Q

What type of hypersensitivity reaction is shown in TB?

A

Type IV

21
Q

What is a common test used to diagnose TB?

A

The Mantoux test for type IV hypersensitivity (tuberculin skin test)

22
Q

List 5 ways that TB avoids phagocytosis

A

1) Evades fusion of the phagolosome
2) Resists acidification of the phagosome
3) Resists degradation in the lysosome
4) The bacteria can escape from the endodosme
5) Metabolic adaptivity means it can persist in many environments

23
Q

What are the 5 sites in humans that can be affects by TB?

A

1) CNS
2) Bones
3) Lungs
4) Pericardium
5) Lymph nodes

24
Q

Is there a vaccination that can be given to prevent development of TB?

A

The BCG vaccine

25
Q

Is TB a notifiable disease?

A

Yes, has to be reported to the local authorities

26
Q

Is Hepatitis B a DNA or a RNA virus?

A

It is a DNA virus

27
Q

What is present in the capsid around the Hep B genome?

A

The Hep B core antigen (HBcAg).

It is not soluble.

28
Q

Outline the process of reverse transcription

A

1) Viral DNA enters cells
2) Transcription and translation produces viral RNA.
3) This single stranded viral RNA is reverse transcribed to DNA which can then be transcribed by the host cell (liver cell).

29
Q

List some clinical features and symptoms of Hep B?

A

1) Dark urine (inability to excrete pigments from haemoglobin)
2) Pale stool
3) Clinical jaundice
4) If untreated, liver cirrhosis and liver death

30
Q

List 4 markers of Hep B infection

A

1) HBsAg
2) anti-HBs
3) anti-HBc IgM
4) anti-HBc IgG

31
Q

Which 2 drugs can be used to treat Hep B?

A

1) INF alpha (alerts organism of abnormal double stranded DNA)
2) Reverse transcriptase inhibitor tenofovir

32
Q

Is there a vaccine that can prevent infection of Hep B?

A

Yes, the HBsAg immunising antigen is injected.

The level of protection depends on the amount of anti-HBs produced.

33
Q

Which vaccines that are given are live attenuated?

A

1) MMR vaccine
2) Rotavirus
3) Small pox
4) Varicella Zoster virus
5) Yellow fever

34
Q

How is HIV infection diagnosed?

A

By detection of serum anti HIV and p24 antigen tests.

35
Q

List 4 ways in which HIV can be transmitted

A

1) Unprotected sex
2) From mother to child, breast feeding
3) Blood transfusions
4) Drug needle use

36
Q

How is the response to antiretroviral drugs detected in HIV?

A

It is monitored by the plasma HIV RNA load and the CD4 lymphocyte count.
If there is viral resistance the viral load will increase and the CD4 count will decrease.

37
Q

How does AIDS cause disease?

A

1) Infects CD4 T lymphocytes.
2) Depletion of CD4 due to cytopathic effects, CD8 T cells killing them, apoptosis of uninfected cells.
3) This impairs the adaptive immune response, generalised immune suppression.

38
Q

List some opportunistic diseases that result from AIDS

A

1) Retinitis
2) Tuberculosis
3) Pneumonia
4) Meningitis
5) Cerebral toxoplasmosis
6) Papilloma viruses
7) EB virus
8) Kaposi’s sarcoma

39
Q

What is Kaposi’s sarcoma?

A

It is a multi centric pigmented sarcoma that presents as lumps in the skin.
Known as human herpes virus 8.
It is latent in endothelial cells, causing angiogenesis and vascular tumours.

Infections and Defence (8 decks)

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