Skin and Soft Tissue Infections Flashcards
Most common organisms associated with skin and soft tissue infections? (2)
Staph aureus
Group A Streptococcus pyogenes
How does the coagulase enzyme produced by staph aureus act as a virulence factor?
Activates fibrinogen and is important in abscess formation
What syndrome does the toxin TSST-1 (toxic syndrome one-1) cause?
Toxic shock syndrome, systemic illness
How does the enzyme hyaluronidase act as a virulence factor?
Produced by staph aureus, lyses fibrin clots and assists in spread of infection
What organism causes scalded skin syndrome in babies?
Staph aureus
Well recognised carriage sites of staph aureus on the human body?
Anterior nares, skin of axilla and groin
How does a capsule act as a virulence factor for streptococcus pyogenes?
Immunological disguise
How does M protein act as virulence factor for streptococcus pyogenes?
Adherence, helps to resist phagocytosis
Which organism produces these toxins: Streptolysin O, Streptolysin S, pyrogenic toxin
Streptococcus pyogenes
Pyrogenic toxin responsible for some of the severe manifestations of necrotising fasciitis
How can you detect the presence of a previous or recent streptococcal infection?
Antibodies to streptolysin O
Where does streptococcus pyogenes normally colonise on the human body?
Nasopharynx
Name the two post streptococcal syndromes
Rheumatic fever
Glomerulonephritis
Arise a few weeks after an infection. Immunologically related.
Aetiology of impetigo?
Staph aureus
Strep pyogenes
Complication of impetigo
Post-streptococcal glomerulonephritis
Treatment for impetigo
Topical fusidic acid/mupirocin
Flucloxacillin
Exclude from school
Strict hygiene, don’t share towels
What is folliculitis?
Superficial infection of hair follicle, caused by staph aureus, pus only in epidermis
What are carbuncles?
Infection of multiple adjacent follicles usually on the back of the neck
Inflammatory mass with multiple sinuses
Patient is often diabetic
What are furuncles?
Commonly known as boils
Infection of hair follicle that extends into dermis with more inflammation that folliculitis
Inflammatory nodule is present often with a hair seen emerging from this
Treatment of larger furuncles/carbuncles?
Incision and drainage
Abx not usually needed
Treatment of recurrent furunculosis
Occurs in staph aureus carriers (carried in their anterior nares) therefore topical MUPIROCIN on the anterior nares
Recurrence also occurs in diabetics
What is erysipela?
Form of cellulitis affecting most superficial layers of skin
More common in infants and elderly
Symptoms of erysipelas
Superficial cellulitis affecting infants and elderly
Abrupt onset with fever, chills, malaise
Raised lesions on red hot area of skin which is well demarcated
What area of the body does erysipelas affect?
Lower legs 70-80%
Face 5-10%
Tx of erysipelas
Penicillin, oral or IV
Which skin layer is affected by cellulitis?
Dermis and subcutaneous fat
Symptoms of cellulitis
Preceded by fever/flu like symptoms
Skin red, hot, swollen (peau d’orange)
Advancing diffuse edge
Risk factors for cellulitis (6)
Obesity Venous insufficiency Lymphoedema Trauma Athletes foot Diabetes
Which organisms cause cellulitis?
MOSTLY will be staph aureus
Or strep pyogenes
BUT in cases of trauma it may be a more unusual cause (eg dog bite with Pasteurella and mixed anaerobes)
Treatment of mild cellulitis?
Oral flucloxacillin (covers both staph and strep)
Treatment of moderate to severe cellulitis?
IV flucloxacillin +/- benzylpenicillin
Treatment of cellulitis with penicillin allergy?
Clindamycin