Microbiology of skin infections Flashcards
How are staph and streps differentiated?
Staphs- gram +ve cocci in CHAINS
Strep- gram +ve cocci in CLUSTERS
How does staph aureus grow on blood agar, and why is this unique?
Produces coagulase (gold colour on blood agar)- all other staphs are coagulase negative
How are streps classified initally?
By haemolysis on blood agar:
Beta= complete (groups A, B, c)
Alpha= partial (strep pneu)
Gamma= none (enterococcus)
Strep epidermidis is not usually pathogenic- in what circumstances might it be?
Prosthetic valves, joint replacements, intravenous catheters
can form biofilms
What skin infections can strep pyogenes be responsible for?
Impetigo
Cellulitis
Infected eczema
Necrotizing fasciitis
What are the recommended treatment regimes for the following organisms/conditions
a) staph aureus
b) strep pyogenes
c) necrotizing fasciitis
d) leg ulcers
a) flucloxacillin
b) penicillin
c) surgical debridement + antibiotic
d) only swab if sign of infection/cellulitis
What is tinea more commonly known as?
Ringworm
Where does tinea affect?
Highly keratinised tissues only e.g. scalp, feet
Which group of patients does scalp ringworm mainly affect?
Children
What is the causal organism in 70% of cases of tinea?
Trichophyton rubrum
How is ringworm treated?
Clotrimazole (canesten)
Itraconazole or terbanafine in intractable/extensive cases
What is the treatment for candida infection?
Clotrimazole cream
Fluconazole (oral)
What are the symptoms of scabies?
Intensely itchy rash in the finger webs, wrists, genitals
How is scabies treated?
Malathion lotion
Benzylbenzoate (not in children)
