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CSP 3 > Bacterial infections in the immunocompromised > Flashcards

Bacterial infections in the immunocompromised Flashcards

1
Q

What characteristics of skin make it an effective barrier to pathogens?

A

low pH
Antimicrobial peptides
Cell sloughing

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2
Q

What type of epithelium is there in the resp tract

A

Ciliated epithelium

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3
Q

How is the urinary tract adapted to protect against pathogens

A
  • Urethral sphincter
  • One way flow
  • Antimicrobial peptides
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4
Q

How does the innate immune system recognise pathogens

A

Pathogen Recognition Receptors such as TLR, C type lectins etc recognise PAMPS
They also express receptors for complement and antibodies

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5
Q

How does the innate immune system kill?

A
  • Phagocytosis and intra-cellular killing

- Release of extracellular substances

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6
Q

Describe the 5 stages of phagocytosis

A 
1- Chemotaxis of phagocyte to microbes
2- Adherence
3- Ingestion of microbes by phagocytes
4- Killing of micobes by enzymes and other chemicals 
5- Elimination
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7
Q

In the innate immune system complement, what does C1q bind to to recognise pathogens?

A

Antibody-antigen complex

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8
Q

What does mannose binding lectin bind to

A

Repeating sugars

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9
Q

What is the main role of the complement system

A

Adjunct in the defence against extracellular pathogens

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10
Q

What is opsonisation

A

Process where microbes are chemically modified and become ‘stuck’ to phagocytes and NK cells

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11
Q

What complement receptor is involved in opsonisation

A

C3b

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12
Q

What phagocyte complement receptor is involved in chemotaxis

A

C3a

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13
Q

Which aspect of the innate immune system is an essential component in response to Neissreia species

A

C5-9

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14
Q

What cells are involved in recognition within humoral immunity

A

B cell receptors recognises extracellular antigens

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15
Q

What are the 3 main actions of the antibodies produced in humoral immunity?

A

1- Neutralisation- antibodies block the binding of pathogens/ toxins to cells
2- Complement activation: C1q binds to Ab-Ab complexes
3- Antibody dependent cytotoxicity

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16
Q

Where are the receptors on the antibody for phagocytes

A

Fc

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17
Q

What are the main roles of humoral immunity

A
  • Preventation of entry of intracellular pathogen (virus, bacteria) into cells
  • Enhanced killing of extracellular pathogens (bacteria and fungi, paracites)
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18
Q

Which antibody fights off multicellular helminths

A

IgE

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19
Q

How do cell mediated immunity recognise pathogens

A

T cell receptors recognise intracellular antigens presented in MHC molecules

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20
Q

What cells express MHC-1 molecules? What about MHC-2?

A

1- all cells

2- antigen presenting cells

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21
Q

What antigens do MHC-1 molecules present? And to what cells?

A
  • MHC-1 molecules present antigens from within the cell cytosol (viruses)
  • Presents to CD8+ cytotoxic T cells
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22
Q

What antigens to MHC-2 molecules present? And to what cells?

A
  • Antigens from within vesicles, such as phagocytosed bacteria
  • Presents to CD4+ cells
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23
Q

What is the action of CD8+ cytotoxic T- cells

A

Kill cells expressing antigens by perforating the cell membrane and inducing apoptosis

24
Q

What is the action of CD4+ T helper cells

A

Mediates the release of TH1, 2 and 17

25
Q

What is the action of Th1

A
  • Stimulate antigen presenting cells to kill intra-cellular pathogens
26
Q

What is the action of Th2

A
  • Stimulate B cells to make antibodies
27
Q

What is the action of Th17

A

-Stimulating epithelial cells to produce antimicrobial peptides

28
Q

Which particular pahogens in Th1 involved in?

A

TB
Salmonella
Leishmania
Toxoplasma

29
Q

Define a commensal organism

A

A micro-organism that derives benefit from another organism without causing damage

30
Q

What is an oppurtunistic pathogen?

A

Pathogen that is generally only able to cause disease in the setting of a weakened immune system

31
Q

What is primary immunodeficiency

A

Immune defect the patient is born with, often due to genetic mutation

32
Q

How can skin be broken, thus leading to worse immunity

A

Surgery, cannula, burns, trauma

33
Q

Which organisms often infect the patient via broken skin

A
  • Skin flora
  • Perineal flora
  • Environmental, usually by innoculation
34
Q

How can mucosa be damaged leading to a deficiency immunity

A

Chemotherapy- leads to mucositis

Broad spectrum abx- leads to altered flora

35
Q

How can the resp barrier be damaged

A

Intubation

36
Q

Which organisms often infect the patient via damaged resp tract

A

Gram negative organisms

Candida

37
Q

Name two primary diseases related to phagocyte deficiency or number

A
  • Chronic granulomatous disease

- Defects in neutrophil migration and granule release

38
Q

Name 3 secondary causes of innate immune defects

A
  • Disease related (AML, aplastic anaemia, diabetes)
  • Chemotherapy associated neutropenia
  • Impaired neutrophil function- eg corticosteroids
39
Q

Which antibiotics can be used in the prophylaxis of innate immune defects relating to phagoctes

A

Quinolones

40
Q

What is a primary cause of an immune defect affecting the complement system

A

Defect in function/ number of complement components

41
Q

Name 2 secondary causes of complement defects

A
  • Eculizumab: a monoclonal abx for C5 (used for acute rejection)
  • Autoantibodies in myeloma
42
Q

A defective membrane attack complex is associated with significantly increased risk of….

A

Neisseria Meningitidis infectoin (meningococcal meningitis & sepsis)

43
Q

Name 5 primary immunodeficiencies associated with impared humoral immune response

A 
SCID
CVID
IgA deficiency
HLA
Hyper IgM
44
Q

Name a disease, a surgical procedure, and 2 medications which result in impaired B-cell number/ function?

A

CLL
Splenectomy
Corticosteroids, rituximab

45
Q

What is the main risk of humoral immune defects

A

Extracellular pathogens (bacteria) that have evolved ways of evading phagocytosis and complement

46
Q

Name 3 encapsulated organisms

A
  • Streptococcus pneumoniae
  • Haemophilus influenza
  • Neisseria meningitis
47
Q

Which organisms commonly invade in IgA deficiency

A

GI pathogens- protozoa (Giardia & Cryptosporidium)

48
Q

Which organisms commonly invade in IgG deficiency

A

Encapsulated organisms

Recurrent sino-pulmonary infection

49
Q

Which type of organisms commonly invade post splenectomy

A

Encapsulated organisms

50
Q

Which organisms invade post splenectomy causing a more severe infection

A
  • Capnocytophaga Canimorsus
  • Babesiosis
  • Malaria
51
Q

What diseases can cause defects in cell mediated immunity (Seconday cause)

A

HIV

Malignancy

52
Q

Name some treatment related causes of cell mediated immunity defects

A 
Anti- rejection medication
Steroids
anti- TNF
Stem cell transplant
Radiotherapy
53
Q

Impact of defects in cell mediated immune defects?

A

Intracellular

54
Q

What does HIV target mainly, and what does it have a ‘knock on effect’ on

A

CD4 cells

Knock on effects to CD8_ and Th2

55
Q

What aspect of the immune system does Anti-TNF therapy target

A

Cell mediated immune defects

56
Q

What does anti-TNF have the biggest impact upon

A

Macrophage responses to intracellular pathogens

57
Q

What features of a patient may lead you to suspect that they are immunocompromised?

A
  • Failure to thrive
  • IV abx user
  • > 4 ear infections in 1/12
  • > 2 or more pneumonias in 1/12
  • Frequent deep skin/ organ abscesse
  • Thrush or cutaneous fungal infection for >6 months
  • Two or more deep seated injections, including septicaemia (blood poisoning) within three years

CSP 3 (9 decks)

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