Infection Flashcards
Define bacteraemia
presence of bacteria in the blood
Define septicaemia
generalised sepsis
Define sepsis
SIRS + documented/presumed infection
Define severe sepsis
SIRS + organ dysfunction/hypoperfusion
shown by hypotension, decreased urine output
Define septic shock
severe sepsis + persistent hypotension despite the administration of fluids
What are the symptoms and signs of acute sepsis?
Fever nausea headache weakness general muscle aches abdominal pain pale and cool extremities fast pulse and respiratory rate low blood pressure
What does SIRS stand for?
Systemic Inflammatory Response Syndrome
What are the criteria for SIRS?
Two or more symptoms present out of: • Temperature 38 • Heart rate >90bpm • Respiratory rate >20/min • WBC 12x10⁹/l
How do microorganisms trigger the inflammatory cascade?
lipopolysaccharide endotoxins on cell wall of gram-negative bacteria trigger the inflammatory cascade
What happens in the inflammatory cascade?
endotoxin binds to macrophages
cytokines released into local environment to recruit reticuloendothelial system
cytokines released into circulation
Why does microvascular thrombosis occur as a result of the inflammatory cascade?
cytokines inititate the production of thrombin
cytokines inhibit fibrinolysis
What is the Sepsis Six?
B - blood cultures U - urine output measurement F - IV fluids A - empirical IV antibiotics L - measure serum lactate O - high flow oxygen
What kind of organism is Neisseria meningitidis?
gram negative
diplococcus
What are the symptoms of meningitis?
- a fever, with cold hands and feet
- vomiting
- drowsiness and difficulty waking up
- confusion and irritability
- severe muscle pain
- pale, blotchy skin, and a distinctive rash (although not everyone will have this)
- a severe headache
- stiff neck
- sensitivity to light (photophobia)
- convulsion or seizures
What are the features of innate immunity?
fast
lacks specificity
lacks memory
no change in intensity
What are the main types of phagocyte?
macrophage
monocyte
neutrophil
How are pathogens recognised by host cells?
PAMPs on microbial structures
recognised by PRRs on phagocytes
How is the attachment of phagocytes to microbes enhanced?
opsonisation
C3b
What processes are cytokines involved in?
chemoattraction
phagocyte activation
inflammation
How is the complement system activated?
alternative pathway
MBL pathway
Describe the alternative pathway of complement system activation
C3b deposits on microbial surface
Bb protein binds to form Alternative Pathway C3 Convertase
Which complement proteins are involved in phagocyte (neutrophil/monocyte) recruitment?
C3a
C5a
Which complement proteins are involved in opsonisation of pathogens?
C3b - C4b
Which complement proteins are involved in killing pathogens and the membrane attack complex?
C5 - C9