Skin infection Flashcards
What are the names for infections in various parts of the skin?
Impetigo – Infection of subcorneal layer of epidermis
Folliculitis – Infection of mouth of hair follicle
Ecythma – Infection of full thickness of epidermis
Boil – Abscess of hair follicle
Carbuncle – Abscess of several adjacent hair follicles
Describe Staph Aureus infection
Is a gram +Ve bacterium
Produces toxins
Commensal bacteria (30% of the population carry it, either in the nostrils or on the skin)
Causes skin infections
Can be MRSA
Can cause infection of bones, joints, and lungs (particularly after influenza) and gives rise to SEPSIS
What toxins can Staph Aureus release?
Panton Valentine Leucodine toxin (virulence factor)
PVL leads to necrotising infection (VERY SERIOUS)
EXFOLIATIVE toxin – cleavage of epidermis blistering
TSST-1 toxin – sickness, fever, malaise. → organ failure
50% of infections with staphylococcus aureus that produce TSST-1 toxin are related to tampons
ENTEROTOXIN – this is a problem in food consumption
Describe Staph Aureus Impetigo
Impetigo from staph infection on epidermis surface
Has honey-coloured crust on eroded base
Mostly around the nose/mouth, can occur anywhere (particularly groin/perineal region)
Bullous impetigo can exist, in which the bacteria is making the exfoliative toxin. Toxin cleaves of the epidermis → extensive blistering. Blisters fairly superficial, easily broken and cause erosions
What is Staph aureus scaled skin syndrome
CAUSE = SA exfoliative toxin enters blood affecting the skin, distant to the origin of the infection → cleavage of epidermis + Desquamation of the epidermis
SYSTEMIC. (Only epithelium) Commonly occurs in children under 5 (immature immune system)
TREAT WITH ANTIBIOTICS and EMOLLIENTS
Recovery takes place in a few days
What may staph aureus scalded skin syndrome be mistaken for?
TOXIC EPIDERMAL NECROLYSIS: widespread desquamation of the skin, as a result of an allergic reaction to a drug.
In TEN, the mucous membranes ARE affected (mouth, eyes and genital areas along with the skin). Staph scalded skin syndrome ONLY affects the skin.
What causes syphilis?
Treponema Pallidum
What are the phases of syphilis?
Primary (at 3-8 weeks): Painless ulcer at inoculation site (Genital or oral)
Secondary (at 6-12 weeks): Disseminated infection, and generalised rash and lymphadenopathy
Tertiary syphilis (usually years later): Skin, neurological and vascular manifestations (e.g thoracic aneurysm)
Tertiary is rare, will only occur if secondary wasn’t treated. Time between phases is asymptomatic
What is congenital syphilis?
Babies have been born to mothers infected with syphilis (trans-placental)
Most result in miscarriage or stillbirth
Babies born alive have features similar to secondary syphilis: rashes
Others asymptomatic but later develop tertiary syphilis symptoms
How is syphilis treated?
Easily treated - easy to test for in serology and responds to penicillin
What are the herpes family of viruses?
HHV1 - HHV8 (All show latency)
What are HHV-1 and HHV-2?
Herpes Simplex Virus types 1 and 2 -
oro-genital herpes
Target: muco-epithelial
latency: neurones
What is HHV-3?
Varicella zoster virus -
Chicken pox and shingles
Target: muco-epithelial
latency: neurones
What is HHV-4?
Epstein–Barr virus -
infectious mononucleosis
Target: B cells
latency: B cells
What is HHV-5?
Cytomegalovirus -
infectious mononucleosis like syndrome, retinitis
Target: Monocyte, epithelial cell
latency: lymphocytes
What is HHV-6?
Roseola virus -
Roseola
Target: Lymphocytes
latency: lymphocytes
What is HHV-7?
HHV-7 -
Pityriasis rosea
Target: T cell
Latency: Lymphocytes
What is HHV-8?
Kaposi Sarcoma associated Herpes virus -
Kaposi Sarcoma
Target: Lymphocytes
Latency: B cells
What can the presentation of herpes simplex cause?
stomatitis - severe inflammation of mouth and lips
What is eczema herpeticum?
Severe HSV infection due to eczema
Patients need intravenous antibiotics, intravenous acyclovir, emollients and topical steroids
Describe HHV-3 latency
The virus enters a period of dormancy, and lives in the dorsal root ganglions of the associated sensory
cutaneous nerves. It can reactivate – causing shingles (herpes zoster infection). This can be bullous – may blister. Patients may suffer from post-herpetic neuralgia
What are Dermatophytes?
Dermatophytes are infecting moulds E.g. Trichophyton rubrum
Dermatophytes live off and grow in keratin (a protein that is part of the skin, hair and nails)
Long hyphae, grow from tip
Dermatophytes cause tinea – this is suffixed by the name of the body part
For example, tinea unguium – a dermatophyte infection of a nail
Describe Tinea unguium
Tinea unguium often presents as a yellow, crumbly nail. It is often pigmented. To confirm that this is a dermatophyte infection, clippings of the nails can be
taken and sent away for culture. This takes 4-6 weeks. The patient needs a 3- month course of anti-fungal tablets – a cream would not work (the creams
cannot penetrate deep enough into the nail matrix).
Describe Tinea Capitis
Dermatophyte infection of the scalp only occurs in children (adults have antifungal chemicals in the sebum of their hair, whereas children do not). This can
be diffuse or localised (kerion).
Some scrapings of the lesion can be cultured for diagnosis of the type of fungus. Patients are given anti-fungals orally (lesion is too deep for topical treatment).
