derm infestation + infect skin Flashcards
important tests for infective cause of derm tissue?
- swabs
- serum
- tissue samples
how does staphyococcus attack the skin?
- receptors that allow it to bind to fibrin: this is found on wound surfaces + in dermatitis
- via panto valentine leukocidin
what can staph infection cause?
Ecthyma
Impetigo
Cellulitis
Folliculitis
- Furunculosis
- Carbuncles
Staphylococcal scalded skin syndrome (SSSS)
Superinfects other dermatoses (e.g. atopic eczema, HSV, leg ulcers)
how does strep attack?
Strepococcus pyogenes (β-haemolytic) attaches to epithelial surfaces via lipoteichoic acid portion of fimbriae
- Has M protein (anti-phagocytic) & hyaluronic acid capsule - Produces erythrogenic exotoxins - Produces streptolysins S and O
how does strep present?
low priority card
Ecthyma
Cellulitis
Impetigo
Erysipelas
Scarlet fever
Necrotizing fasciitis
Superinfects other dermatoses (e.g. leg ulcers)
what is eosinophilic (non infectious) folliculitis associated with?
HIV
treatment for folliculitis?
Antibiotics (usually flucloxacillin or erythromycin)
Incision and drainage is required for furunculosis.
folliculitis recurrent cases may arise from?
from nasal carriage of Staphylococcus aureus, particularly strains expressing Panton-Valentine leukocidin (PVL).
What is the difference between a furuncle and a carbuncle?
A furuncle is a deep follicular abscess
- Involvement with adjacent connected follicles = Carbuncle.
Carbuncle - 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 microbial flora:
-abundant nasal flora
Immune deficiency:
- Hypogammaglobulinaemia
- HyperIgE syndrome – deficiency
- Chronic granulomatous disease
- AIDS
- Diabetes Mellitus
Where is Staphylococcus aureus most abundant?
nasal flora
Panton Valentine Leukocidin Staphylococcus Aureus features?
Beta pore forming exotoxin
Leukocyte destruction and tissue necrosis
Higher morbidity, mortality and transmissibility
Skin:
- Recurrent and painful abscesses
- Folliculitis
- Cellulitis
- Often painful, more than 1 site, recurrent, present in contacts
extracutaneous Panton Valentine Leukocidin Staphylococcus Aureus symptoms?
- Necrotising pneumonia
- Necrotising fasciitis
- Purpura fulminans
Panton Valentine Leukocidin Staphylococcus Aureus : risks
5 Cs
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 to treat Panton Valentine Leukocidin Staphylococcus Aureus
Consult local microbiologist/ guidelines
Antibiotics
Decolonisation:
* Chlorhexidine body wash for 7 days
* Nasal application of mupirocin ointment 5 days)
Treatment of close contacts
What is Pseudomonal Folliculitis associated with amd how does it present?
hot tub use, swimming pools and depilatories, wet suit
Appears 1-3 days after exposure, as a diffuse truncal eruption.
Follicular erythematous papule
treatment of Pseudomonal Folliculitis?
usually none required
Rarely can cause abscesses, lymphangitis + fever
- severe/recurrent cases treated with oral ciprofloxacin
What is cellulitis?
Infection of lower dermis and subcutaneous tissue
Tender swelling with ill-defined, blanching erythema or oedema
what predisposes to cellulitis and whats causes it?
Predisposed by oedema
Most causes caused by s.pyogenes and s. aures
how to treat cellulitis?
systemic ABs
Features of impetigo
Superficial bacterial infection
Looks like stuck-on, honey-coloured crusts overlying an erosion.
Often affects face
What causes impetigo?
Streptococci (non-bullous)
or
Staphylococci (bullous)
Caused by exfoliative toxins A & B, split epidermis by targeting desmoglein I.
How to treat impetigo?
topical +/- systemic antibiotics.
Impetiginisation observations?
Occurs in atopic dermatitis
- Gold crust - Staphylococcus aureus
What is Ecthyma?
Severe form of streptococcal impetigo
Thick crust overlying a punch out ulceration surrounded by erythema
Usually on lower extremities
Who’s at risk of Staphylococcal Scalded Skin Syndrome
Neonates, infants or immunocompromised adults
What is the cause of scalded skin syndrome (not organism, but the toxin!)
Due to exfoliative toxin
Why can’t the organism be cultured from denuded skin in scalded skin syndrome?
Infection occurs at distant site (ie conjunctivitis or abscess)
The organism can’t be cultured from the site of skin damage
How does staphylococcal scaled skin syndrome affect neonates?
→ Diffuse tender erythema
→ Rapid progression to flaccid bullae,
→ Wrinkle and exfoliate, leaving oozing erythematous base
In neonates, kidneys cannot excrete the exfoliative toxin quickly
What does scalded skin syndrome look like?
Stevens-Johnson syndrome / toxic epidermal necrolysis
What causes toxic shock syndrome?
Group A Staphylococcus aureus strain that produces pyrogenic exotoxin TSST-1
signs of toxic shock syndrome
Fever >38.9°C Hypotension Diffuse erythema Involvement of multiple systems: – Gastrointestinal – Muscular – CNS - Renal - Hepatic Effects mucous membranes (erythema) Hematologic (platelets <100 000/mm3) Desquamation predominantly of palms and soles 1-2 weeks after resolution of erythema
What causes erythasma?
Infection of Corynebacterium minutissimum
Well demarcated patches in intertriginous areas
(e.g. armpit)
- initially pink
- Become brown and scaly
Pitted Keratolysis cause + treatment
- Caused by Corynebacteria
2. Treated with topical clindamycin.
Erysipeloid cause?
Erysipelothrix rhusiopathiae
- looks like cellulitis but slower spreading
- Associated with handling contaminated raw fish or meat.
Anthrax organism?
Bacillus anthracis
How does anthrax present?
Painless necrotic ulcer with surrounding oedema and regional lymphadenopathy (with pain in lymph nodes) at the site of contact with: hides bone meal wool or infected with Bacillus anthracis
Blistering Distal Dactylitis - rare- what causes it?
Streptococcus pyogenes or Staphylococcus aureus
who suffers with Blistering Distal Dactylitis
young children
signs/symptoms 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 and what are causes and symptoms?
Infection of deep dermis and subcutis
Caused by B- haemolytic streptococci or s. aures
Painful
Prodrome of malaise, fever, headache
Presents as erythematous indurated plaque with a sharp demarcated border and a cliff drop edge (+/- blistering)
May effect face or limb:
- red streak of lymphangitis and local lymphadenopathy
how to treat Erysipelas?
IV ABs
Scarlet fever cause?
Caused by upper respiratory tract infection with erythrogenic toxin-producing Streptococcus pyogenes
Cause of necrotising fasciitis
streptococci, staphylococci, enterobacteriaceae and anaerobes.
when Necrotising fasciitis affects the scrotum?
(Fournier’s gangrene).
Which group is more vulnerable to Atypical Mycobacterial Infection
people in immunocompromised states
What does Mycobacterium marinum cause
indolent granulomatous ulcers (fish-tank granuloma) in healthy people
- Sporotrichoid spread
What can cause Mycobacterium chelonae?
puncture wounds, tattoos, skin trauma or surgery
What Mycobacterium ulcerans lead to?
an important cause of limb ulceration in Africa (Buruli ulcer) or Australia (Searle’s ulcer).
Borreliosis (Lyme Disease) manifestation?
Annular erythema develops at site of the bite of a Borrelia-infected tick
Bite from Ixodes tick infected with Borrelia burgdorferi
Initial cutaneous manifestation- erythema migrans (only in 70%):
- erythematous papule at bite site
-progression to annular erythema of >20cm
What happens 1-30 days after initial bite in lyme disease?
infection, fever, headache Multiple secondary lesions develop - similar but smaller to initial lesion Neuroborreliosis - Facial palsy / other CN palsies - Aseptic meningitis - Polyradiculitis Arthritis – painful and swollen large joints (knee is the most affected join) Carditis
How to diagnose lyme disease?
Serology not sensitive
Histopathology - non-specific
High index of suspicion required for diagnosis
Cause of Tularaemia
Francisella tularensis
Acquired through:
- Handling infected animals (squirrels and rabbits) - Tick bites - Deerfly bites
systemic symptoms + signs of tularaemia
systemic: fever, chills, headache and malaise
other: Painful regional lymphadenopathy
Ecthyma Gangrenosum cause
Pseudomonas aeruginosa
Who is @ risk of Ecthyma Gangrenosum
neutropaenic patients
development of Ecthyma gangrenosum
Red macule(s) → oedematous → haemorrhagic bullae.
May ulcerate in late stages or form an eschar surrounded by erythema
cause of syphilis
Treponema pallidum
progression of syphilis
Primary infection Chancre -painless ulcer with a firm indurated border
Painless regional lymphadenopathy one week after the primary chancre
Chancre appears within 10-90 days
why is it hard to diagnose syphilis when looking at signs/symptoms secondary symphilis?
Great mimicker’ – low threshold for testing
- Rash (88-100%) -Pityriasis rosea-like rash - Alopecia (‘moth-eaten’) - Mucous patches - Lymphadenopathy - Residual primary chancre - Condylomata lata - Hepatosplenomegaly
secondary syphilis signs/symptoms
Malaise, fever, headache, pruritus, loss of appetite, iritis
What is Lues maligna?
Rare manifestation of secondary syphilis
Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
More frequent in HIV manifestation
Tertiary syphilis
(5)
Gumma Skin lesions - nodules and plaques
Extend peripherally while central areas heal with scarring and atrophy
Mucosal lesions extend to and destroy the nasal cartilage
Cardiovascular disease
Neurosyphilis (general paresis or tabes dorsalis)
how to diagnose symphilis?
Clinical findings
Serology
Strong index of suspicion required in 2ndary syphilis
How to treat syphilis?
IM benzylpenicillin or oral tetracycline
Leprosy cause?
Mycobacterium leprae
features of Lepromatous leprosy
Multiple lesions: macules, papules, nodules
- Sensation and sweating normal (early on)
features of Tuberculoid leprosy
Solitary or few: elevated borders – atrophic center, sometimes annular
- Hairless, anhidrotic, numb
how can cutaneous TB be acquired?
- Exogenously (primary-inoculation TB and tuberculosis verrucosa cutis)
- Contiguous endogenous spread – (scrofuloderma )or autoinoculation – periorificial tuberculosis
- Haematogenous/lymphatic endogenous spread –dissemination (lupus vulgaris, miliary tuberculosis, gummas)
investigations TB
- Interferon-γ release assay (Quantiferon-TB)
- Histology – ZN stain
- Culture / PCR
TB cutaneous manifestations
Tuberculous chancre - painless, firm, reddish-brown papulonodule that forms an ulcer
Tuberculosis verrucosa cutis - wart-like papule that evolves to form redbrown plaque
Scrofuloderma – subcutaneous nodule with necrotic material - becomes fluctuant and drains, with ulceration and sinus tract formation.
Orificial TB - non-healing ulcer of the nasal mucosa that is painful
Lupus vulgaris – red brown plaque - +/- central scarring, ulceration
Miliary TB - pinhead-sized, bluish-red papules capped by minute vesicles
Tuberculous gumma – firm subcutaneous nodule - later ulcerates
Molluscum Contagiosum common in who?
children + immunocomprmised
Molluscum Contagiosum cure?
Usually resolve spontaneously
Herpes Simplex Virus: HSV-1 infection?
direct contact with contaminated saliva / other infected secretions
Herpes Simplex Virus: HSV-2 infection?
sexual contact
how does herpes simplex travel?
Travels by retrograde axonal flow to dorsal root ganglia
What type of eczma can result of herpes simplex virus?
Eczema herpeticum
emergency
Monomorphic, punched out erosions (excoriated vesicles)
Herpes gladiatorum risk factor
Contact sports e.g. wrestling
HSV 1 involvement of cutaneous site reflecting sites of contact with another athlete’s lesions
how to treat neonatal herpes simplex virus
Requires IV antivirals
Encephalitis → mortality >50% without treatment, 15% with treatment → neurological deficits
how to treat herpes simplex virus
Don’t delay
Oral valacyclovir or acyclovir 200mg five times daily in immunocompetent localised infection
Intravenous 10mg/kg TDS X 7-19 days
Hand foot and mouth disease cause
Coxsackie A16, Echo 71
how to treat hand foot and mouth disease
don’t - usually self limiting
Which viruses cause morbilliform (measles-like) eruptions
Measles, Rubella, EBV, CMV, HHV6 & HHV7 cause morbilliform (measles-like) eruptions
Leptospirosis
Rickettsia
Erythema Infectiosum cause
Parvovirus B19
causes of Roseola infantum
by HHV6 and HHV7 (less commonly)
Orf causes
parapoxvirus
-> due to Direct exposure to sheep or goats
important superficial fungal infections to know
- malassezia
2. Dermatophytes
disseminated fungal infection to know
aspergillus
Pityriasis versicolor treatment
Topical azole
Kerion: what is it?
an inflammatory fungal infection that may mimic a bacterial folliculitis or an abscess of the scalp; scalp is tender and patient usually has posterior cervical lymphadenopathy
Aspergillosis risk factors
: neutropaenia & corticosteroid therapy]-> primarily resp pathogen
Propensity to invade blood vessels causing thrombosis and infarction
Lesions destructive – may extend into cartilage, bone and fascial planes
Mucormycosis cause
Apophysomyces, Mucor, Rhizopus, Absidia, Rhizomucor
Treatment consists of aggressive debridement and antifungal therapy
Culture positive in only 30% of cases
Scabies cause
Sarcoptes species
Female mates, burrows into upper epidermis, lays her eggs and dies after one month.
Insidious onset of red to flesh-coloured pruritic papules
Affects interdigital areas of digits, volar wrists, axillary areas, genitalia
diagnosis of scabies
- diagnostic burrow of fine white scales often seen
treatment of scabies
permethrin, oral ivermectin
- Two cycles of treatment are required
treating head lice
malathion, permethrin, or oral ivermectin
treating body lice
thorough cleaning or discarding clothes
treating Pubic Lice
malathion / permethrin, oral ivermectin
treating bed bugs
fumigation of homes
What are symptoms of scarlet fever and how does it present?
Preceded by sore throat, headache, malaise, chills, anorexia and fever
Eruption begins 12-48 hrs later:
