Professional Pathogen Flashcards
S. aureus virulence
- Adherence to nasal mucosa
- Adhesins
- Ability to invade tissues
- Cytotoxins
- Enzymes
- Ability to evade immune clearance
- Protein A
- Capsule
- Ability to replicate and disseminate
list the three skin infections caused by S. aureus
Furunculosis - boils
Impetigo - strain with exfoliative enzymes
Staph Abscess
S. aureus line sepsis
The S aureus migrates up the PICC line into the body and causes blood infection where it disseminates around the body.
S. aureus infections
- Normal commensal
- Pathogen in skin / soft tissue infections
- Surgical site infections
- Vascular line related infections
- Bacteraemia – commonest cause
- Endocarditis
- Osteomyelitis
- Septic arthritis
- Almost anywhere else
- Food poisoning - caused by enterotoxins
What has gram negative wall got that +ve doesn’t?
Lipopolysaccharide
How is LPS recognised?
How does the body respond?
•LPS interacts with Toll-Like Receptors (esp. TLR4) on
- Monocyte / macrophage lineage cells
- Endothelium
•Results in activation of
- Inflammatory pathways
- Coagulation and clotting pathways
- Changes in endothelial integrity
Streptococcus pneumoniae virulence
- Specific adhesins for respiratory mucosa
- Pneumolysin
- binds host cell membrane cholesterol
- Forms pores and lyses in ciliated cells
- Lyses host phagocytic cells
•Secretory IgA protease
-breaks down secreted immunoglobulin A, preventing mucosal clearance
•Capsule
- Polysaccharide coat prevents complement-mediated phagocytosis
- Specific antibodies to capsule required
- >100 different capsular types
C difficile pathogenicity
•Makes toxins – cause fluid secretion into gut
- Diarrhoea
- Increased infectivity
•Production of spores
- Difficult to control cross infection
- Relapse on treatment
•Some virulent strains (027)
- Lose regulation of toxin genes – hyper-producers
- Produce additional toxins
