Filling in the blanks Flashcards
What is the most likely causes of endocarditis?
Viridans streptococci
Then:
- S. aureus
- Enterococcus faecalis
How is endocarditis diagnosed?
- Fever + Heart murmur (could also have embolic phenomena,
- 3x blood test 20 mins apart, continuous bacteraemia (isolated pathogen)
What is the treatment for endocarditis?
Empiric: Penicillin, flucloxicillin, gentamicin
Defined therapy following isolation of bacteria:
S. viridans = Penicillin
S. aureus = Flucoxicillin (vancomycin if MRSA)
What are the most likely causes of septic athritis?
S. aureus… then S. pyogenes
What are the virulence factors of S. pyogenes?
Adhesion:
- MSCRAMMS
Immune evasion:
- Hyaluronic acid capsule (prevents opson & phago)
- M protein (Binds factor H, prevents CB3 opson)
- Streptolysin O (lyse immune cells)
- C5a peptidase
- DNases (degrade neutrophils EC traps)
- SpyCEP (destroys IL8)
Invasion:
- Streptokinase (activates plasminogen)
- Hyaluronidase
- Proteases
- Lipases
What is the most likely causes of osteomyelitis? route of infection?
S. aureus (80%) and then S. pyogenes
(trauma, local spread I.e SSTI or diabetic ulcer, heamatogenous route)
What are the virulence factors of s. aureus?
Adhesion:
- MSCRAMMS
Spreading factors:
- Staphylokinase (plasiminogen)
- Lipases
- DNases
- Cytolysins i.e heamolysin or leukocidin
Immune evasion factors:
- Cytolysins
- Capsule (prevents opson and phago)
- Slime layer
- Protein A (binds IgG wrong orientation)
- Cell bound coagulase (forms clot to hide)
- Superantigens (heat resistant proteins)
What is the thought process of a pt with a fever&cough?
Must further define the upper resp tract infection
- i.e otitis media vs sinusitis etc
- This picture then enables a probable organsism
bad phargynitis = S pyogenes? in child treat, adult dont bother.
Sinusitis = rhinovirus? dont treat
How do you distinguish bronchitis from pneumonia?
Pneumonia = Fever + cough
Bronchitis = Cough
What are the virulence factors of pneumococcoal?
PSPA= binds epithelium and prevents C3B deposition
PSPC= prevents activation of compliment cascade
Pili = Colonisation and activates TNFa
Polysaccharide capsule = Prevents phagocytosis and complement deposition
Pneumolysin = Lyses neutrophils and epithelial cells
Choline binding protein = Binds Ig receptor on cells- allows transport into cells
How would you treat a s. pneumonia infection?
- Penicillin (but resistance on rise) so consider macrolide (developing world scenario) (this works by targeting 50s transpeptidation on ribosomes (bacteriacidal) or quinolones.
What are the most likely pathogens of peritonitis?
E. coli most common gram negative
B fragilis most common anaerobe
Usually combination of gram negative, anaerobes and enterococci
What antibiotics would you want to use in pertionitis? what specifically if ESBL E. coli is indentified?
Wanting to cover aerobic (i.e gram neg e coli), anaerobic (b fragilis) +/- enterococci
- Amoxycillin + Gentamicin + Metronidazole
or
- Cefuroxime + Metronidazole (if not covering enterococci)
Meropenam is also a broad spectrum antibiotic (ESBL E. coli)
What is used to treat cryptococcal neoformans meningitis?
IV Amphotericin B (amphiterrible, now go straight to azoles)
IV fluconazole
What are the virulence factors of n meningitidis:
- Polysaccharide capsule
- Binds factor H down regulating compliment
- Type N pilli bind compliment down regulating it
- Expresses different lipopolysaccharide blobs similar to human blood antigens. Also can release blobs of LPS to decoy
