Week 3 - Meningitis and innate immunity

Question 1

What is sepsis?

Answer 1

The systemic response to infection

- Systemic inflammatory response syndrome + documented or presumed infection

Question 2

What is severe sepsis?

Answer 2

SIRS + organ dysfunction/hypoperfusion

Question 3

What is septic shock?

Answer 3

Severe sepsis + persistently low blood pressure (despite administrating intravenous fluids)

Question 4

What is septicaemia?

Answer 4

A clinical term meaning generalised sepsis

Question 5

What is bacteraemia?

Answer 5

The presence of bacteria in the blood

Question 6

What is Systemic Inflammatory Response syndrome (SIRS)?

Answer 6

A response to a non-specific insult (e.g. anaemia, trauma, infection, etc.)
2 or more of:
- Temperature: 38ºC
- Heart rate: >90/min
- Respiratory rate: >20/min
- WBC:  12x 10^9 /L

Question 7

What is the inflammatory cascade?

Answer 7

• Endotoxin binds to macrophages
• Cytokines released locally
• – Stimulate inflammatory response to promote wound repair
• Cytokines released into the circulation
• – Stimulates growth factor, macrophages and platelets
• Homeostasis is not restored if patient has SIRS

Question 8

How do cytokines cause shock and multiorgan failure?

Answer 8

• Initiate production of thrombin so promote coagulation
• They also inhibit fibrinolysis
• Coagulation leads to microvascular thrombosis and hence:
• – Organ ischaemia
• – Organ dysfunction
• – Organ failure
• Microvascular injury is the major cause of shock and multiorgan failure

Question 9

What is the sepsis 6?

Answer 9

• Deliver high flow oxygen
• Take blood cultures and other cultures, consider source control
• Administer empirical IV antibiotics
• Measure serum lactate
• Start IV fluid resuscitation
• Commence accurate urine output measurement

Question 10

What are the symptoms of meningitis?

Answer 10

• Feel acutely unwell
• Fever
• Severe headache
• Nausea
• Weakness
• General muscle pain
• Abdominal pain
• Photophobia (eye pain on exposure to light)
• Pale, cool extremities
• Temp = high
• Pulse = high
• BP = low
• Widespread purpuric rash (non-blanching)
• Neck stiffness
• Mentally alert

Question 11

What are some life-threatening complications of meningitis?

Answer 11

• Irreversible hypotension
• Respiratory failure
• Acute kidney injury
• Raised intracranial pressure
• Ischaemic necrosis of digits/hands/fingers

Question 12

What are the different types of barriers to infection?

Answer 12

• Physical
• Physiological
• Chemical
• Biological

Question 13

What physical barriers are there to infection?

Answer 13

• Skin
• Mucous membranes (mouth, respiratory tract, vagina, GI tract, urinary tract)
• Bronchial cilia

Question 14

What physiological barriers are there to infection?

Answer 14

• Diarrhoea
• Vomiting
• Coughing
• Sneezing

Question 15

What chemical barriers are there to infection?

Answer 15

• Low pH
• – Skin 5.5
• – Stomach 1-3
• – Vagina 4.4
• Antimicrobial molecules (e.g. IgA, lysozyme, mucus, gastric acid + pepsin, beta-defensins)

Question 16

What biological barriers are there to infection?

Answer 16

Normal flora

• Non-pathogenic microbes in strategic locations
• Always absent in internal organs/tissues
• Compete with pathogens for attachment sites and resources
• Provide antimicrobial chemicals
• Synthesise vitamins
• Can cause infection if they are displaced from their normal location and moved to a sterile location