skin infections and infestations basics Flashcards
things caused by staphylococcus aureus
impetigo folliculitis cellulitis ecthyma staohylococcal scalded skin syndrome superinfections of other skin diseases e.g leg ulcers, atopic eczema
What immune deficiencies make you more prone to bacterial infections?
Hypogammaglobulinaemia
HyperIgE syndrome
AIDS
Diabetes Mellitus
conditions caused by streptococcus pyogenes
impetigo cellulitis ecthyma eysipelas scarlet fever necrotising fasciitis superinfects other skin diseases e.g leg ulcers
PVL toxin - panton valentine leukocidin
s.aureus toxin
pore forming, painful, multi site, recurrent and present in contact
painful
necrotising fasciitis, pneumonia, purpura fulminans
preventing PVL infection
close contact contaminated items crowding cleanliness cuts
treatment of PVL infection
antibiotics
nasal mupirocin ointment
chlorhexidine body wash
treat any contacts
what is folliculitis
follicular erythema, can be pustular
infections or non infectious (HIV)
treated by antibiotics - erythormicin
incision and drainage for furunculosis (large)
what is pseudomonal folliculitis (hot tub)
pseudomonas aeruginosa
associated w moisture, 1-3 days post exposure to hottub etc
self limiting
furuncle vs carbuncle
furuncle - deep abcess of one follicle
carbuncle - deep abscess of several adjacent follicles (can cause cellulitis or septicaemia)
what is cellulitis
infection of lower dermis/subcut tender swelling with ill defined blanching erythema/odemea usually strep pyogenes or s.aureus odema predisposes treated by systemic antibiotics
what is impetigo
superficial bac infection, honey coloured crust
caused by staphylococcus
affects face
treated with topical and systemic antibiotics
what is impetiginisation
infection of atopic eczema
staph aureus
gold crust
what is lyme disease (borreliosis)
target shaped (annular erythema)
infected tick bite
carditis and arthritis and neuroborriolis (facial palsy, aseptic meningitis, polyradiulitis)
what is the initial presentation 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
What is secondary syphilis, what are the symptoms?
Begins 50 days after chancre
Presents with malaise, fever, headache, pruritus, loss of appetite, iritis
Why is syphilis referred to as the great mimicker?
Presents with a wide range of symptoms such as
Rash
Alopecia
Mucous patches
Lymphadenopathy
Residual primary chancre
Hepatosplenomegaly
What is lues maligna in syphilis?
Rrae manufestation of secondary syphilis
Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
More frequent in HIV manifestations
What is tertiary syphilis?
Gumma skin lesions - nodules and plaques
Extend pripherally while central areas heal with scarring and atrophy
Mucosal lesions extend and destroy the nasal cartilage
Cardiovascular disease
Neurosyphilis
How is syphilis diagnosed?
Clinal findings
Serology
Strong index of suspicion required in secondary syphilis
What is the treatment for syphilis?
IM benzylpenicilin or oral tetracycline
What is herpes simplex virus?
Primary and recurrent vesicular eruptions favouring orolabial and genital regions
Travels by retrograde axonal flow to dorsal root ganglia
What are the two types of HSV?
HSV-1 – direct contact with contaminated saliva / other infected secretions
HSV-2 - sexual contact
What is HSV preceded by?
Preceded by tender lymphadenopathy, malaise, anorexia
± Burning, tingling
What may cause reactivation of HSV?
Reactivation – spontaneous, UV, fever, local tissue damage, stress
What is the systemic manifestation of HSV?
aseptic meningitis in 10% of omen
What is eczema herpeticum?
Emergency
Monomorphic punched or erosions (excoriated vesicles)
What is herpetic whitlow?
HSV (1>2) infection of digits – pain, swelling and vesicles (vesicles may appear later)
Misdiagnosed as paronychia or dactylitis
Often in children
What causes neonatal HSV?
Exposure to HSV during vaginal delivery – risk higher when HSV acquired near time of delivery
what are some features of neonatal HSV?
HSV 1 or 2
Onset from birth to 2 weeks
Localised usually – scalp or trunk
Vesicles → bullae erosions
Encephalitis → mortality >50% without treatment, 15% with treatment → neurological deficits
Requires IV antivirals
What is severe or chronic HSV, how does it present, other involvements?
Immunocompromised patients e.g. HIV / transplant recipient
Most common presentation – chronic, enlarging ulceration
Multiple sites or disseminated
Often atypical e.g. verrucous, exophytic or pustular lesions
Involvement of respiratory or GI tracts may occur
How is HSV diagnosed?
Swab for PCR
What is the treatment for HSV?
Don’t delay
Oral valacyclovir or acyclovir 200mg five times daily in immunocompetent localised infection
Intravenous 10mg/kg TDS X 7-19 days
What is pityriasis versicolor?
Superficial fungal infection
Hypopigmented, hyperpigmented or erythematous macular eruption +/- fine scale
Malassezia spp.
When does pityriasis versicolor tend to begin?
Adolescence when sebaceous glands become active
What causes flares in pityriasis versicolor?
When temperatures and humidity are high
Treatment for pityriasis versicolor?
Topical azole
What are dermatophytes?
Fungi that live on keratin
What two fungi cause the most fungal infections and tinea capitis?
Trichophyton rubrum and trichophyton tonsurans
What is a kerion?
– 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
- Frequently secondarily infected with Staphylococcus aureus
What are Id reactions?
Dermatophytid reactions
Inflammatory reactions at sites distant from the associated dermatophyte infection
May include urticaria, hand dermatitis, or erythema nodosum
Likely secondary to a strong host immunologic response against fungal antigens
What is the a common cause of vulvovaginitis?
Candiasis
What is candidiasis predisposed by?
occlusion, moisture, warm temperature, diabetes mellitus
What are the usual presentations of candidiasis?
Most sites show erythema oedema, thin purulent discharge
Usually an intertriginous infection (skin folds) or of oral mucosa.
What type of fungal infection is mucormycosis?
Opportunistic
Typical presentation of mucormycosis?
oedema, then pain, then eschar
fever, headache proptosis, facial pain, orbital cellulitis ± cranial nerve dysfunction
What is mucormycosis associated with?
Diabetes mellitus (1/3 of patients - DKA very high risk
Malnutrition
Uraemia
Neutropaenia
Medications: Steroids / antibiotics / desferoxamine
Burns
HIV
What is the treatment for mucormycosis?
aggressive debridement & antifungal therapy amphoteracin
What is scabies?
Contagious infestation caused by 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
Where does scabies usually affect?
Affects interdigital areas of digits, volar wrists, axillary areas, genitalia
