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Sepsis > host microbe interactions > Flashcards

host microbe interactions Flashcards

1
Q

wha tis the initial protection provided by the immune system

A

physical barriers

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2
Q

what are the two components of the immune system?

A

innate (phagocytes/ NK cells)

acquired/adaptive (B cells/ T cells)

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3
Q

different parts of the immune system control

A

different types of organisms

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4
Q

what is the role of physical barriers?

A

protection from infection

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5
Q

what increases the risk of infection?

A

damage/ inflammation to these barriers

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6
Q

skin

A

Keratinocytes secrete antimicrobial peptides (defensins)
Sebaceous/sweat glands secrete microbe-inhibiting substances (e.g. fatty acids)
Antigen-presenting cells in skin

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7
Q

mucosa of respiratory?GI/GU tract

A

Antimicrobial substances e.g. lysozyme
Secretory immunoglobulin A (IgA)
Gastric acid

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8
Q

susceptibility due to impaired barrier - skin

A

Eczema, psoriasis, erythroderma
Tinea pedis / cracking of skin
Ulcers / pressure sores

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9
Q

susceptibility due to impaired barrier - lungs

A

Cystic fibrosis / Bronchiectasis
COPD
Poor swallow (often due to neurological illness, e.g. previous stroke)

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10
Q

susceptibility due to impaired barrier - GI

A

Mucositis secondary to chemotherapy
Inflammatory bowel disease
Bowel cancer

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11
Q

susceptibility due to impaired barrier - GU

A

Impaired bladder emptying / catheterisation

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12
Q

what parts of the immune system fight against infection?

A

phagocytes
T-lymphocytes
B-cells

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13
Q

what are phagocytes?

A

neutrophils and macrophages

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14
Q

what is the role of phagocytes?

A

ingest organisms following opsonisation, killing via oxygen dependent or independent mechanisms

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15
Q

phagocytes are responsible for controlling infection from?

A

bacteria and fungi
Strep, Staph, coliforms etc.
Aspergillus, Candida

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16
Q

deficiencies or impaired function of phagocytes tend to be seen in?

A 
Haematological malignancy (esp acute leukaemia, myelodysplasia)
Cytotoxic chemotherapy
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17
Q

role of helper T-lymphocytes (CD4+)

A

CD4+ T cells activate phagocytes to kill microbes

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18
Q

role of cytolytic T-lymphocyte (CD8+)

A

CD8+ T cells destroy infected cells containing microbes or microbial proteins

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19
Q

T lymphocytes control?

A

large number of infections, co-ordinate responses

20
Q

deficiency of T-lymphocytes causes a range of susceptibilities in?

A

Viruses, fungi, mycobacteria and parasites (mostly intracellular organisms)

21
Q

deficiencies of T-lymphocytes tend to be seen in?

A 
HIV infection (acquired deficiency in CD4+ lymphocytes)
Lymphoma
Primary immunodeficiency syndromes (e.g. SCID)
22
Q

where do B lymphocytes mature?

A

into the plasma cell and produce immunoglobulins

23
Q

immunoglobulins protect against?

A

recognised antigens
IgM produced first – weak affinity
IgG produced subsequently – strong affinity

24
Q

Antibodies also help?

A

opsonize microbes for ingestion by phagocytes:

bacteria and virus

25
Q

deficiencies/imapired function of antibodies tend to be seen in

A

Myeloma (paraproteinaema with immune paresis)
Primary immunodeficiency syndromes
Certain immune suppressants (e.g. rituximab)

26
Q

HIV infects?

A

CD4+ T lymphocytes

27
Q

how does HIV cause a reduction of CD4+ lymphocytes?

A

progressive decline, resulting in cell mediated immunity

28
Q

those with HIV have a high risk of?

A

invasive pneumococcal (S. pneumonia) disease (bacteraemia/meningitis/empyema etc.) irrespective of CD4 count

29
Q

CD4 <350

A

Mycobacterium tuberculosis, candidiasis

30
Q

CD4<200

A

Pneumocystis jirovecii, Toxoplasma gondii

31
Q

CD4<100

A

Cryptococcus neoformans, Cytomegalovirus (CMV)

32
Q

hyposplenism

A

decreased spleen function

33
Q

splenectomy

A

trauma ITP lymphoma etc

34
Q

“functional: hyposplenism

A

sickle cell, cirrhosis, coeliac disease

35
Q

hyposplenism: host susceptibility to invasive infection from

A 
encapsulated organisms 
Streptococcus pneumoniae (pneumococcus)
Haemophilus influenzae type B (HiB)
Neisseria meningitidis (meningococcus)
36
Q

how to reduce risk of hyposplenism?

A

Risk can be reduced by vaccination (preferably before splenectomy)
along with amoxicillin to prevent infection from pneumococci

37
Q

elderly patients are:

A

Elderly patients more prone to infections

Less able to distinguish self from non-self – autoimmune disorders more common

38
Q

immune system of the elderly?

A

Phagocytes destroy bacteria /antigen more slowly
T cells respond more slowly
Less antibody is produced and it binds to antigen less well
Less complement is produced

39
Q

immune suppression is caused by?

A

Variety of drugs used for range of conditions
Aim is to reduce damage due immune response
Autoimmune conditions
Transplants
Cancers

40
Q

autoimmune conditions that cause immune suppression?

A 
Inflammatory arthritis
Vasculitis / connective tissue diseases
Glomerulonephritis
Inflammatory bowel disease
Interstitial lung disease
ITP / autoimmune haemolytic anaemia
41
Q

transplants and immune suppression

A 
Solid organ (kidney/heart/lung/liver/pancreas/small bowel)
Bone marrow (particularly with graft vs host disease)
42
Q

cancer and immune suppression

A

“Biologics” used especially in breast/lung/liver cancer and melanoma

43
Q

effects of immunocompromised?

A

blunted response to stimuli
Often do not exhibit same symptoms and signs as “normal people”
Fever may be absent
Lack of inflammatory response (CRP / neutrophilia)
Non-specifically unwell, no localising features
Often lower threshold for treatment
Need to consider wider range or possible organisms

44
Q

spectrum of immunocompromised?

A

Wide range of drugs used
Often combinations of drugs
“Level” of immunosuppression varies widely with condition treated, e.g.
Acute leukaemia treated with bone marrow transplant
Severe (life threatening) vasculitis / connective tissue diseases
ITP / AIHA
”Mild” inflammatory bowel disease

45
Q

steroid associations

A

wide range of infection

particularly strong association with fungal infections (Candida, aspergillum)

46
Q

anti-TNFa therapy associations?

A

Anti-TNFa therapies (e.g. Infliximab/Etanercept)
Strong association with Mycobacterium tuberculosis
Fungal infections (Aspergillus in particular)

47
Q

purine analogue associations?

A

(e.g. fludarabine/cytarabine)
Viral infections (especially Herpes Simplex Virus and Varicella Zoster Virus)
Pneumocystis jirovecii

Sepsis (8 decks)

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