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Infection And Immunity > Sepsis and Innate Immunity > Flashcards

Sepsis and Innate Immunity Flashcards

1
Q

Define sepsis

A

Life threatening organ dysfunction due to a dysregulated host response to infection

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2
Q

Define septic shock

A

Persisting hypotension requiring treatment to maintain blood pressure despite fluid resuscitation already being given

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3
Q

Define bacteriaemia

A

The presence of bacteria in the blood
Not multiplying
No symptoms

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4
Q

What does the early warning score for sepsis look for?

A

Increased resp rate
Increased heart rate
Very low or high temperature
Low blood pressure

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5
Q

What is included in the sepsis six bundle?

A 
Give high flow oxygen
Give IV fluids 
Give empirical IV antibiotics 
Take blood for cultures
Take blood for lactate 
Check the urine output
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6
Q

Apart from the sepsis six bundle, what other investigations should you order?

A 
FBC
U&E
EDTA bottle for PCR 
Blood sugar
LFTs
CRP 
Coagulation studies
Blood gases
Other microbiology samples (CSF, urine)
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7
Q

What is the most likely organism causing meningitis?

A

Neisseria meningitidis

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8
Q

How is meningitis spread?

A

Direct contact with respiratory secretions

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9
Q

What are the local effects of cytokines?

A

Promote wound repair

Recruit the reticuloendothelial system

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10
Q

What are the systemic effects of cytokines?

A

Stimulating growth factor, macrophages and platelets to control infection

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11
Q

How can cytokines in sepsis lead to organ ischaemia?

A

Initiate production of thrombin
Promote coagulation
Cytokines also inhibit fibrinolysis
Microvascular thrombosis

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12
Q

Describe the management for sepsis

A

Sepsis six bundle
Consider early referral to ITU
Regular monitoring and reassessment

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13
Q

What antibiotic do we use to treat meningitis?

A

Ceftriaxone

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14
Q

Describe neisseria meningitidis

A 
Gram negative diplococcus 
Numerous types - B is most common in UK
Type based on capsular antigen 
Up to 25% young adults are carriers
Spread by aerosols and nasal secretions
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15
Q

What types of meningitis are covered in the multiple vaccine?

A

ACWY

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16
Q

Define infectivity

A

Capacity of microorganism to establish itself within the host

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17
Q

Define virulence

A

Capacity of the pathogen to harm the host

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18
Q

What is the immune system?

A

All the cell and organs that contribute to the immune defences against infectious and non-infectious conditions
Distinguishing between self and non-self

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19
Q

Define an infectious disease

A

When the pathogen succeeds in evading and/or overwhelming the host’s immune defences

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20
Q

What are the roles of the immune system?

A

Pathogen recognition
Containing/eliminating the infection
Regulating itself
Remembering pathogens

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21
Q

Name the 4 types of barriers that are the first line of defence

A

Physical
Physiological
Chemical
Biological

22
Q

Describe the physical barriers of defence

A

Skin (epidermis has no vessels so cannot spread that way)

Mucous membranes - active and dynamics, secrete antimicrobials, cilia

23
Q

Describe some physiological barriers against infection

A

Diarrhoea
Vomiting
Coughing
Sneezing

24
Q

Describe the chemical barriers against infection

A

Low pH of the skin, stomach and vagina - Bacteria are extremely sensitive to acidic environments
Antimicrobial molecules: IgA (tears, salvia), Lysozyme (perspiration, urine, sebum), mucus, beta-defensins (epithelium), gastric acid

25
Q

Describe the benefits of normal flora

A

Compete with pathogens for attachment sites and resources
Produce antimicrobials
Synthesis vitamins (K, B12 and other B vitamins)

26
Q

Give some examples of normal flora of the skin

A 
Staph aureus 
Staph epidermidis
Strep pyogenes
Candida albicans 
Clostridium perfringens
27
Q

Give some examples of normal nasopharyngeal flora

A

Strep pneumoniae
Neisseria meningitidis
Haemophilus species

28
Q

List some patients who are high risk when present with bacteriaemia

A

Asplenic/hyposplenic
Damaged/prosthetic valves
Previous infective endocarditis

29
Q

What pathologies can lead to overgrowth of normal flora?

A

Diabetes
AIDS
Malignancy
Chemotherapy

30
Q

What are the 3 main phagocytes?

A

Macrophages
Monocytes
Neutrophils

31
Q

Describe the features of macrophages

A

Present in all organs
Ingest and destroy microbes
Present antigens to T cells
Produce cytokines/chemokines

32
Q

Describe the features of monocytes

A

Present in blood

Recruited at infection site and differentiate into macrophages

33
Q

Describe the features of neutrophils

A

Present in the blood
Increased during infections
Recruited by cytokines to site of infection
Ingest and destroy microbes

34
Q

What are PAMPs?

A

Pathogen-associated molecular patterns
Present on the microbe
What the phagocytes use to recognise it
Can be carbohydrate, lipid, protein or nucleic acid

35
Q

Define opsonisation

A

Coating proteins called opsonins that bind to microbial surfaces leading to enhanced attachment of phagocytes and clearance of microbes

36
Q

Give some examples of opsonins

A

Component - C3b, C4b
Antibodies - IgM, IgG
Acute phase proteins - CRP, MBL

37
Q

Encapsulated bacteria cannot be cleared unless …

A

Opsonised

38
Q

Give examples of some encapsulated bacteria

A

Neisseria menigitidis
Strep pneumoniae
Haemophilus influenzae B

39
Q

What are the steps of phagocytosis?

A 
Chemotaxis and adherence to microbe 
Ingestion
Formation of phagosome
Fusion with lysosome
Digested on microbe by enzymes 
Formation of residual body containing indigestible material
Discharge of waste material
40
Q

What are the 2 types of phagocyte killing mechanisms?

A 
Oxygen dependent (respiratory burst)
Oxygen independent
41
Q

What factors contribute to the oxygen independent killing mechanism?

A

Lysozyme
Lactoferrin/transferrin
Cationic proteins
Proteolytic and hydrolytic enzymes

42
Q

How may complement proteins are there?

A

20

43
Q

Describe the 2 complement activating pathways

A

Alternative - initiated by cell surface microbial constituents
MBL - initiated when MBL binds to mannose containing residues of proteins found on many microbes

44
Q

Which complement proteins recruit phagocytes?

A

C3a and C5a

45
Q

Which complement proteins contribute to the membrane attack complex?

A

C5-C9

46
Q

What are the actions of TNF-alpha, IL-1 and IL-6?

A 
CRP and MBL released
Neutrophil mobilisation 
Vasodilation 
Vascular permeability 
Adhesion molecules attract neutrophils 
Increase body temperature
47
Q

Why are asplenic people susceptible to encapsulated bacteria?

A

They have reduced phagocytosis

The spleen normally contains many macrophages

48
Q

How can e-coli be caught?

A 
Eating contaminated food
Touching infected animals 
Contact with people who have the illness
Drinking inadequately treated water
Swimming/playing in contaminated water
49
Q

Main symptoms of E-coli infection:

A

Diarrhoea
Fever
Stomach cramps
(Can last up to 2 weeks)

50
Q

Describe a few basic features of E-coli

A

Gram negative
Rod-shaped
Anaerobic

51
Q

Describe a few basic features of strep pneumoniae

A 
Gram positive
Anaerobic 
Present in many healthy carriers
Main cause of CAQ pneumonia
Transmission: sneezing, coughing, direct contact 
Encapsulated

Infection And Immunity (9 decks)

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