302 Bacterial pathogenesis and sepsis Flashcards
What in the membrane makes gram negative bacteria negative?
Lipopolysaccharide and proteins and pores on the outside
What are the different classifications of streptococci?
alpha: haemolytic (partial)
Beta: haemolytic (complete)
Gamma: non-haemolytic
Samples of what, from the body, are usually sterile?
urine and blood
Where is staph aureus a normal commensal of?
The nose (60%)
Which bacteria mainly causes cellulitis
Streptococcus pyogenes
What is necrotising fasciiatis?
A deeper strep pyogenes infection with signs of sepsis
It gets deeper and behaves differently and releases extensive tissue damage
How do you recognise necrotising fasciatis?
-Out of proportion pain
-Bruising and blistering
-Generalised toxaemia
-Renal impairment
-Very high CRP
-Raised creatine kinase sometimes
What are the superficial infections causes by strep pyogenes?
Pharyngitis
Cellulitis
What are the deeper infections caused by strep pyogenes?
Severe soft tissue infection
myositis
Necrotising fasciitis
What are some autoimmune sequalae of s.pyogenes infection?
Rheumatic fever
Glomerulonephritis
Why is lipopolysaccharide considered an endotoxin?
It stimulates a powerful immune response
Which bacteria is a common contaminant of urine and blood?
Staph epidermidis
What host responses in sepsis causes further disease
Dissemination
Cellular damage
Organ damage
What is SIRS?
Systemic inflammatory response syndrome
What are some cardiovascular changes in sepsis?
Early distributive shock (warm peripheries)
-Peripheral vasodilatation
Then hypovolaemic shock (cold peripheries)
-Capillary leak, peripheral and pulmonary oedema
-Low filling pressure (fluid responsive)
Late cardiogenic shock (cold peripheries)
-Cardiac myocyte suppression
-High filling pressure (not fluid responsive)
