skin infection/ infestation Flashcards
What is Panton Valentine Leukocydin?
Staphylococcus receptor that allows it to bind to fibrin that is found in abundance on wound surfaces and in dermatitis
What skin infections does staphylococcus play a role in?
Echtyma
Impetigo
Cellulitis
Folliculitis (furunculosis, carbuncles)
Staphylococcal scalded skin syndrome (SSSS)
Superinfects other dermatoses (atopic eczema, leg ulcers, HSV)
What kind of hemolysis does streptococcus pygenes carry out?
B hemolysis
Describe the virulence of streptococcus pygenes
Attaches to epithelial surfaces via lipoteichoic acid portion of fimbriae
Has M protein (anti-phagocytic) and hyaluronic acid capsule
Produces erythrogenic exotoxins
Produces streptolysins S and O
What skin infections does streptococcus play a role in?
Echthyma Impetigo Cellulitis Erysipelas Scarlet Fever Necrotising fasciitis Superinfects other dermatoses (leg ulcers)
What does the cutaneous manifestation of folliculitis look like?
Follicular erythema, sometimes papular
Is folliculitis infection or non-infectious?
May be infectious or non-infectious
Eosinophilic (non-infectious) folliculitis is associated with HIV
What could cause recurrent folliculitis?
Nasal carriage of staphylococcus aureus, particularly strains expressing PVL
How is folliculitis treated?
Antibiotics, usually flucloxacillin or erythromycin
Incision and drainage is required for furunculosis
What is the difference between a furuncle and a carbuncle?
A furuncle is a deep follicular abscess
Involvement with adjacent connected follicles- carbuncle
Cabuncles are more likely to lead to complications such as cellulitis and septicaemia
Why do some patients develop recurrent staphylococcal impetigo or recurrent furunculosis?
Establishment as part of the resident microflora
-abundant in nasal flora
Immune deficiency
- chronic granulomatous disease
- AIDS
- Diabetes mellitus
- Hypogammaglobulinemia
- Hyper IgE syndrome- deficiency
What kind of toxin does PVL Staphylococcus aureus produce and what are its effects?
B-pore forming toxin
Leukocyte destruction and tissue necrosis
Higher morbidity, mortality and transmission
skin: recurrent and painful abscesses, folliculitis, cellulitis (often painful, recurrent, more than 1 site, present in contacts)
extracutaneous: necrotising pneumonia, necrotising fasciitis, purpura fulminans
What are the risk factors for acquiring PVL Staphylococcus aureus?
5Cs
Close contact (hugging, contact sports)
Crowding (living in crowded accommodation like boarding school, military accommodation, prison)
Cleanliness (of environment)
Contaminated items (gym equipment, towels, razors
Cuts and grazes (allowing bacteria to enter body)
How is PVL staphylococcus aureus treated?
Consult local mocrobiologist/ guidelines
Antibiotics (often tetracycline)
Decolonisation often:
chlorhexidine body wash for 7 days
nasal application of mupirocin ointment, 5 days. )
Treatment of close contacts
What is acquiring pseudomonas folliculitis associated with?
Hot tub use, swimming pools, wet suit, depilatories
Describe the symptoms of pseudomonas folliculitis
Appears 1-3 days after exposure as a diffuse truncal eruption
follicular erythematous papule
rarely: abcesses, lymphangitis, fever
How is pseudomonas folliculitis treated?
Most cases are self limited- no treatment required
Sever or recurrent cases can be treated with oral ciprofloxacin
What is cellulitis and how does it manifest?
Infection of lower dermis and subcutaneous tissue
tender swelling with ill define, blanching erythema or oedema
What is a predisposing factor for cellulitis?
Oedema
What are the causative organisms of cellulitis?
Most commonly streptococcus pyogenes and staphylococcus aureus
What is the treatment for cellulitis?
Systemic antibiotics
Describe impetigo manifestation
Superficial bacterial infection with stuck on, honey coloured crusts overlying an erosion
What organisms caused impetigo?
Streptococci (non-bulbous)
Staphylococci (bulbous)
caused by exfoliating toxins A and B
which split epidermis by targeting desmoglein I
What parts of the body does impetigo often affect?
Face (perioral, ears, nares)
How is impetigo treated?
Topical +/- systemic antibiotics
In what skin condition can impetigisation occur and what causes it?
Atopic dermatitis (gold crust) staphylococcus aureus
What is echthyma?
What does it look like?
Sever form of streptococcal impetigo
Thick crust overlying a punch out ulceration surrounded by erythema
Usually on lower extremities
What is echthyma?
What does it look like?
Sever form of streptococcal impetigo
Thick crust overlying a punch out ulceration surrounded by erythema
Usually on lower extremities
In what groups of people does staphylococcal scalded skin syndrome generally occur?
Neonates, infants, immunocompromised adults
What kind of toxin causes staphylococcal scalded skin syndrome?
Exfoliative toxin
In neonates, kidneys cannot excrete the exfoliative toxin quickly
Why can organism not be cultured from denuded skin in staphylococcal scalded skin syndrome ?
Infection occurs at distant site (e.g. conjunctivitis, abscesses
Describe the progression of staphylococcal scalded skin syndrome.
diffuse tender erythema that rapidly progresses to flaccid bullae that wrinkle and exfoliate, leaving an oozing erythematous base
clinically resembles SJS/TEN
What organism causes toxic shock syndrome?
Group A Staphylococcus aureus strain that produces pyogenic exotoxin TSST-1
What are the symptoms of TSS?
Fever >38.9 0C
Hypotension
Hematologic (platelets <100,000/mm3)
Systemic involvement (Renal, Hepatic, GI, Muscular, CNS)
Diffuse erythema
Mucous membranes
Desquamation predominantly of palms and soles 1-2 weeks after resolution of erythema
What organism causes erythrasma?
Corynebacterium minitissimum
Describe the cutaneous manifestation of erythrasma
Well demarcated patches in intertriginous areas
Initially pink, become brown and scaly
What is pitted keratolysis?
Pitted erosions of the soles
What organisms cause pitted keratolysis?
Corynebacteria
How is pitted keratolysis treated?
Topical clindamycin
What occurs in erysipeloid?
Erythema and oedema of the hand after handling contaminated raw fish or meat
extends slowly over weeks
What organism causes erysipeloid?
Erysipelothrix rhusiopathiae
What organism causes anthrax?
Bacillus anthracis
How does anthrax manifest?
Painless necrotic ulcer with surrounding oedema and regional lymphadenopathy (with pain in lymph nodes) at site of contact with hides, wool or bone meal infected with Bacillus anthracis
What organisms cause blistering distal dactylitis?
Streptococcus pyogenes
Staphylococcus aureus
In what group of the population does blistering distal dactylitis commonly occur?
Typically young children
Describe the cutaneous manifestation of blistering distal dactylitis.
One or more tender superficial bullae on an erythematous base on the volar fat pad of finger
toes may be rarely affected
What is erysipelas?
Infection of deep dermis and subcutis
What organisms cause erysipelas?
Staphylococcus aureus
B-hemolytic streptococci
Describe the symptoms of erysipelas.
Painful
Prodrome of fever, malaise, headache
presents as erythematous indurated plaque with a sharply demarcated border and cliff drop edge (+/- blistering)
Face or limb +/- red streak of lymphangitis and local lymphadenopathy
Name a possible portal of entry in erysipelas.
Tinea pedis
How is erysipelas treated?
Intravenous antibiotics
In which part of the population does scarlet fever occur?
Primarily a disease of children
What causes scarlet fever?
Upper respiratory tract infection with erythrogenic toxin producing streptococcus pyogenes
What are the symptoms of scarlet fever?
Preceded by fever, malaise, headache, sore throat, chills, anorexia
Eruption begins 12-48 hours later: blanch able, tiny pinkish red spots on chest, neck and axillae that spreads to the whole body within 12 hours. Sandpaper like texture.
What are the complications of scarlet fever?
Otitis, mastoiditis, sinusitis, pneumonia, myocarditis, rheumatic fever, meningitis, hepatitis, acute glomerulonephritis
What occurs in necrotising fasciitis?
Initial dusky induration (usually of a limb), followed by rapid painful necrosis of skin, connective tissue and muscle.
Potentially fatal
What organisms cause necrotising fasciitis?
Usually synergistic: streptococci, staphylococci, enterobacteriae and anaerobes
How is necrotising fasciitis treated?
Prompt diagnosis is essential (requires high index of suspicion), followed by broad-spectrum parenteral antibiotics and surgical debridement.
MRI can aid diagnosis.
Blood and tissue cultures can determine organisms and sensitivities.
What are the complications of necrotising fasciitis?
Mortality is high
Can affect scrotum (Fournier’s gangrene)
In what kind of individuals does atypical mycobacterial infection occur?
Immunocompromised
Give examples for atypical mycobacterium infection.
Mycobacterium marinum: causes indolent granulomatous ulcers (fish tank ulcer) in healthy adults. Sporotrichoid spread.
Mycobacterium chelonae and abscessus: puncture wounds, tattoos, skin trauma or surgery
Mycobacterium ulcerans: important cause of limb ulceration in Africa (Buruli ulcer) or Australia (Searle’s ulcer)
What causes borreliosis/ Lyme disease?
Bite from an Ixodes tick infected with Borrelia burgdorferi
What is the initial cutaneous manifestation of borrelia/ Lyme disease?
Erythema migraines (only in 75%)
- erythematous papule at bite site
- progression to annular erythema >20cm
How does Lyme disease progress?
Fever, headache 1-30 days after infections
multiple secondary lesions develop (similar to initial lesion but smaller)
What are complications of Lyme disease?
Neuroborreliosis- facial/ other CN palsies, aseptic meningitis, polyradiculitis
Arthritis- painful and swollen large joints (knee is the most affected joint)
Carditis
How is Lyme disease diagnosed?
Serology not sensitive
Histopathology- non specific
High index of suspicion required for diagnosis
What organism causes tularaemia?
Francisella tularensis
How is tularaemia acquired?
Handling of infectious animals (rabbits, squirrels)
Tick bites
Deerfly bites
How does tularaemia present?
Ulceroglandular form
Primary skin lesion is small papules at inoculation site which rapidly necroses- leading to painful ulceration
+/- local cellulitis
Painful regional lymphadenopathy
Systemic symptoms: fever, headache, malaise, chills