Bacterial infections of the skin Flashcards
What are two bacteria that commonly cause bacterial infections of the skin?
Staph Aureus, Streptococcus
How does staph aureus express its virulence factors?
Binding to cell fibrin, found in abundance in wound surfaces such as ulcers and jt dermatitis
Virulence factors expressed by Staph A.
Haemolysin
Leukocidin
a-toxin
exfoliative toxin
PVL
What types of conditions can staph aureus cause?
Ecthyma,
Impetigo,
Cellulitis,
Folliculitis,
SSSS (Staph scalded skin syndrome)
Superinfects other skin conditions e.g. herpes
How does streptococcus express its virulence factors?
Attaches to cell epithelium (lipoteichoic acid) using M protein (anti-phagocytic) and hyaluronic acid capsule
What virulence factors does streptococcus express?
Erythrogenic Exotoxins, gives skin red appearance
Streptolysins S and O, causes cells to break apart
What types of conditions can streptococcus cause?
Ecthyma,
Impetigo,
Cellulitis,
Erysipelas
Scarlet Fever,
Necrotising Fasciitis
Folliculitis
Inflammation of the hair follicle
How does folliculitis manifest
Follicular erythema, redness around the follicle
sometimes pustular, pus producing
What is another term for non-infectious folliculitis?
Eosinophilic Folliculitis
associated with HIV
How can recurrent cases of folliculitis arise?
Reservoir of Staph A. esp in nasal cavity.
(especially panton-valentine leukocidin - PVL - expressing strains)
What is the treatment for folliculitis?
Antibiotics - erythromycin
incision and drainage for furunculosis
Furuncle vs Carbuncle
Furuncle is a deep follicular abscess
Carbuncles are clusters of multiple boils, when the abscess involves multiple follicles
What are carbuncles likely to lead to?
Cellulitis and Septicaemia
Why are staph aureus infections so recurrent?
Microbial abundance in nasal flora
Immune deficiency (AIDS, DM)
What is a strain of staph aureus that has a higher morbidity, mortality and transmissibility?
Panton Valentine Leukocidin Staphylococcus Aureus
PVL
What is PVL staph A. characterised by
Leukocyte destruction
tissue necrosis
What are the skin signs of PVL Staph Aureus?
Recurrent painful abscesses, folliculitis and cellulitis (in multiple sites)
What are the extracutaneous signs of PVL Staph Aureus?
Necrotising Pneumonia,
Necrotising Fasciitis,
Purpura Fulminans - patches of dark purple skin, due to haemorrhage and thrombosis