Skin infestations and infections Flashcards
What receptors does staphyloccus have?
receptors that allow it to bind to fibrin that is found in abundance on wound surfaces and in dermatitis
What are examples of conditions staphyloccus can form?
- Panton Valentine Leukocidin
- Ecthyma
- Impetigo
- Cellulitis
- Folliculitis
- Staphylococcal scalded skin syndrome (SSSS) - toxic shock syndrome
- Superinfects other dermatoses (e.g. atopic eczema, HSV, leg ulcers)
What are different types of folliculitis?
- Furunculosis
- Carbuncles
What are the difference virulence factors in steptoccous?
- Strepococcus pyogenes (β-haemolytic) attaches to epithelial surfaces via lipoteichoic acid portion of fimbriae
2, Has M protein (anti-phagocytic) & hyaluronic acid capsule - Produces erythrogenic exotoxins
- Produces streptolysins S and O
What presentations can streptoccocus show?
- Ecthyma
- Cellulitis
- Impetigo
- Erysipelas
- Scarlet fever
- Necrotizing fasciitis
- Superinfects other dermatoses (e.g. leg ulcers)
What is folliculitis?
Follicular erythema; sometimes pustular
Is folliculitis infectious?
infectious or non infectious
What type of folliculitis is associated with HIV?
Eosinophilic (non-infectious) folliculitis
When can there be recurrent episodes of folliculitis?
- from nasal carriage of Staphylococcus aureus
2. particularly strains expressing Panton-Valentine leukocidin (PVL)
What is the treatment of folliculitis?
- Antibiotics (usually flucloxacillin or erythromycin)
2. Incision and drainage is required for furunculosis
What is a furuncle?
deep follicular abscess
What is a carbuncle?
deep follicular abscess
with involvement with adjacent connected follicles
What can a carbuncle lead to?
more likely to lead to complications such as cellulitis and septicaemia
Why do some patients develop recurrent staphylococcal impetigo or recurrent furunculosis?
- Establishment as a part of the resident microbial flora
- Abundant in nasal flora - Immune deficiency
What immune deficiency can lead to some patients develop recurrent staphylococcal impetigo or recurrent furunculosis?
- Hypogammaglobulinaemia
- HyperIgE syndrome – deficiency
- Chronic granulomatous disease
- AIDS
- Diabetes Mellitus
What is panton valentine leukocidin (PVL)?
- β-pore-forming exotoxin
* Leukocyte destruction and tissue necrosis
What is the effect of panton valentine leukocidin?
Higher morbidity, mortality and transmissibility
How does PVL affect the skin?
- Recurrent and painful abscesses
- Folliculitis
- Cellulitis
- Often painful, more than 1 site, recurrent, present in contacts
What are the extracutaneous manifestations of PVL?
- Necrotising pneumonia
- Necrotising fasciitis
- Purpura fulminans
What are the 5Cs to getting PVL?
- Close Contact – e.g. hugging, contact sports
- Contaminated items , e.g. gym equipment, towels or razors.
- Crowding –crowded living conditions such as e.g. military accommodation, prisons and boarding schools.
- Cleanliness (of environment)
- Cuts and grazes – having a cut or graze will allow the bacteria to enter the body
How do you treat PVL?
- Consult local microbiologist / guidelines
- Antibiotics (often tetracycline)
- Decolonisation
- Treatment of close contacts
How do you deconlinse PVL?
- Chlorhexidine body wash for 7 days
2. Nasal application of mupirocin ointment 5 days)
What is pseudomonal folliculitis associated with?
hot tub use, swimming pools and depilatories, wet suit
When does pseudonomal follicultis appear?
1-3 days after exposure, as a diffuse truncal eruption
What happens during pseudonomal folliculitis?
- Follicular erythematous papule
* Rarely: abscesses, lymphangitis and fever
How do you treat pseudomonal folliculitis?
- Most cases self-limited – no treatment required.
* Severe or recurrent cases can be treated with oral ciprofloxacin
What is cellulitis?
- Infection of lower dermis and subcutaneous tissue
* Tender swelling with ill-defined, blanching erythema or oedema
What are most cases of cellulitis? What are predisposing factors?
- Streptococcus pyogenes
- Staphylococcus aureus
- Oedema is a predisposing factor
What is the treatment of cellulitis?
systemic antibiotics
What is impetigo?
Superficial bacterial infection, stuck-on, honey-coloured crusts overlying an erosion
What is impetigo caused by?
- Streptococci (non-bullous)
2. Staphylococci (bullous)
What is staphylococci impetigo caused by?
exfoliative toxins A and B, split epidermis by targeting desmoglein I
Where does impetigo usually affect?
face (perioral, ears, nares)
What is impetigo treated by?
topical +/- systemic antibiotics
What is impetiginisation?
- Occurs in atopic dermatitis
- Gold crust
- Staphylococcus aureus
What is ecthyma?
Severe form of streptococcal impetigo
Where does ecthyma happen?
- Thick crust overlying a punch out ulceration surrounded by erythema
- Usually on lower extremities
When does staphylococcal scalded skin syndrome (SSSS) happen?
Neonates, infants or immunocompromised adults
Why does SSSS happen?
- Due to exfoliative toxin
- Infection occurs at distant site (ie conjunctivitis or abscess)
- So Organism cannot be cultured from denuded skin
Why do neonates get SSSS?
kidneys cannot excrete the exfoliative toxin quickly
What happens with neonates at SSSS?
- Diffuse tender erythema that 2. Rapid progression to flaccid bullae
- Wrinkle and exfoliate, leaving oozing erythematous base
What does SSSS clinically resemble?
Stevens-Johnson syndrome / toxic epidermal necrolysis
What is toxic shock syndrome?
Febrile illness due to Group A Staphylococcus aureus strain that produces pyrogenic exotoxin TSST-1
What are the symptoms of toxic shock syndrome?
- Fever >38.9°C
- Hypotension
- Diffuse erythema
What systems are involved in toxic shock syndrome?
•Involvement of ≥ systems: – Gastrointestinal – Muscular – CNS - Renal - Hepatic
What else is involved in toxic shock syndrome?
- Mucous membranes (erythema)
- Hematologic (platelets <100 000/mm3)
- Desquamation predominantly of palms and soles 1-2 weeks after resolution of erythema
What is erythrasma due to?
Infection of Corynebacterium minutissimum
What happen in erythrasma?
•Well demarcated patches in intertriginous areas
- initially pink
- Become brown and scaly
What is pitted keratolysis?
Pitted erosions of soles
What is pitted keratolysis due to?
Caused by Corynebacteria
What is pitted keratolysis treated with?
topical clindamycin
What is erysipeloid?
Erythema and oedema of the hand after handling contaminated raw fish or meat
How quick does erysipeloid spread?
- Extends slowly over weeks.
* Erysipelothrix rhusiopathiae
What is anthrax?
- Painless necrotic ulcer with surrounding oedema and regional lymphadenopathy (with pain in lymph nodes)
- at the site of contact with hides, bone meal or wool
- infected with Bacillus anthracis.
What is blistering distal dactylitis?
Rare infection caused by Streptococcus pyogenes or Staphylococcus aureus
Who gets blistering distal dactylitis?
Typically - young children
What are the signs of blistering distal dactylitis?
- 1 or more tender superficial bullae on erythematous base on the volar fat pad of a finger
- Toes may rarely be affected
What is erysipelas?
Infection of deep dermis and subcutis
What is erysipelas caused by?
- β-haemolytic streptococci
2. Staphylococcus aureus
What are the symptoms of erysipelas?
- Painful
- Prodrome of malaise, fever, headache.
- Presents as erythematous indurated plaque with a sharply demarcated border and a cliff-drop edge
+/- blistering - Face or limb
+/- red streak of lymphangitis and local lymphadenopathy.
-Portal of entry must be sought (e.g. tinea pedis).
-Systemic symptoms (fever, malaise).
How is erysipelas treated?
intravenous antibiotics
What is Scarlet fever caused by?
upper respiratory tract infection with erythrogenic toxin-producing Streptococcus pyogenes
What is Scarlet fever preceded by?
- sore throat
- headache
- malaise
- chills
- anorexia
- fever
- Eruption begins 12-48 hours late
What is the eruption of Scarlet fever like?
-Blanchable tiny pinkish-red spots on chest, neck and axillae
-Spread to whole body within 12 hours
- Sandpaper-like texture
What are the complications of Scarlet fever?
- otitis
- mastoiditis
- sinusitis
- pneumonia
- myocarditis
- hepatitis
- meningitis
- rheumatic fever
- acute glomerulonephritis
