Skin bone joint infections Flashcards
(53 cards)
What are the two main pathogens that cause SSSIs?
S. aureus and Streptococcus pyogenes
SSSI meanign
Skin/skin structure infection
What does virulence factors does S. aureus have?
Coagulase
Hyaluronidsase
Catalse
Protein A
Haemolysins
Lipase
Protease
Staphylokinase
What does virulence factors does Strep. pyogenes have?
Capsule
Adhesins
Anti-opsonic factors
Streptolysin O/S
Hyaluronidase
Streptokinase
What is coagulase used for by bacteria
Forming blood clots
Why is catalse a virulence factor?
Allows neutralisation of ROSs e.g H2O2
What is protein A (s.aureus)
Binds to the Fc region of immunoglobulins (IgG), enabling the bacteria to evade the host’s immune system and impair phagocytosis.
Why are haemolysins virulence factors?
Lyse RBCs
Streptolysin function (O and S)
cell damage
Hyaluronidase function in bacteria
Degrade hyaluronan which partly makes up connective tissue
Streptokinase function
Thrombolytic agent, meaning it dissolves blood clots by activating plasminogen and converting it into plasmin, which then breaks down fibrin clots
Staphylokinase function
Activates plasminogen to form plasmin, which digests fibrin clots
Give 5 reasons why the skin is inhospitable to microbes
Dry
Constant shedding
Low pH
Sebaceous secretions
Competition with resident microbiota
Direct introduction of microbe into the epithelium leads to formation of what lesion
Papilloma
Pathway of arriving circulating micorbes/toxins (this heavily differs)
Macule (flat, red) –> Papule (raised, red), vesicle (small blister) –> ulcer (epithelium rupture)
Define folliculitis + 2 causes
Superficial infection of hair follicle. Caused by S. aureus or Ps. Aeruginosa (hot tub folliculitis).
Define furuncle/boil
Deep folliculitis, involves single follice
Define carbuncle
Collection of furuncles with are connected subcutaneously, lesion extends into subcutaneous fat. (Can’t just give antibiotic, need to debride)
Define impetigo + causative agents
Superficial skin infection, highly infectious. Caused by Group A streptococci/ S. aureus. Disruption of corneal layer access to sub corneal keratinocytes.
Staphylococcal scaled skin syndrome is mostly in what age group
6 and below
Causative agent of Staphylococcal scaled skin syndrome
S. aureus elaborating exfloliative exotoxin
Why is mortality rate of Staphylococcal scaled skin syndrome higher in adults
Due to higher surface area
Define erysipelas and cause
Superficial form of cellulitis, bright red lesion on the face or lower extremities. Caused by Group A streptococci. Confined.
Define cellulitis anc causes
Rapidly spreading infection of skin and underlying tissues (subcutaneous fat). Group A strep like S. aureus, P. aeruginosa anaerobes (Fournier’s gangrene or otherwise called necrotising fasciitis of the perineum). Can lead to sepsis
