6. Skin Infections Flashcards
What is the epidemiology of skin disease?
Where is it more common?
- Skin disease is common – 15% of GP appointments are skin related (25% due to skin infection).
- 5% of dermatologist appointments are due to skin infections.
- Skin conditions are more common in hot, humid climates amongst poorer populations (opposite in dry/rich).
What are the features of Staphylococcus aureus?
Features of SA:
- A gram+ bacteria, commensal in approx. 30% of humans with colonisation in the nose, axilla and groin.
- SA is the most common bacterial cause of skin infections including – impetigo (and bullous (blistering) impetigo), folliculitis, ecthyma, boils and carbuncles.
What diseases can Staphylococcus aureus cause?
What are the treatments?
Diseases caused
– via the production of toxins, SA can cause:
- o Staphylococcal Scalded Skin Syndrome – Exfoliative toxin.
- o Toxic shock Syndrome – Toxic Shock Syndrome Toxin 1 (TSST-1).
- o Food poisoning – Enterotoxin.
- o Necrotising soft tissue infections – Panton Valentine Leucocidin virulence factor.
Treatment – infections all treated with antibiotics, there is no vaccine.
What are the features of treponema pallidum and what does it cause?
Features of TP:
- A gram- spirochaete and the cause of Syphilis (which is usually an STI).
What are the stages of syphilis?
How can it be transmitted and what is its treatment?
Stages of Syphilis:
- o Primary – painless ulcers (chancre) at site of inoculation.
- o Secondary – disseminated infection with rash (maculopapular) and lymphadenopathy.
- o Latent – asymptomatic period.
- o Tertiary – skin (gummatous skin lesions, bone lesions), neurological and vascular manifestations.
Transmission: Syphilis can be VERTICALLY transmitted and cause congenital syphilis.
Treatment: No vaccine is available but the infection can be treated with antibiotics.
What are the features of HSV and what are the two types?
Herpes Simplex Viruses 1 & 2
Features of HSV:
- o Members of the human herpes virus (HHV) family which are DNA viruses.
- o Type 1 – causes oral infections.
- o Type 2 – causes genital infections.
What is the pathogenesis of HSV and what is its treatment?
Herpes Simplex Viruses 1 & 2
Pathogenesis:
- o Transmission by direct contact.
- o Clinical features involve – painful vesicular rash (heals over 2-4 weeks), eczema herpeticum, herpes encephalitis.
- o Due to latency in sensory involvement, there can be reactivation with reoccurrences of infection.
Treatment: No vaccine is available, outbreaks treated with anti-viral medication such as acyclovir.
Draw a table showing the 3 types of HHV (1,2,3) with their:
- synonym
- target cell
- disease
- site of latency
What are the features and pathogenesis of VZV?
What is its treatment?
Varicella Zoster Virus
Features of VZV:
- o Another human herpes virus as seen above.
Pathogenesis:
- o Primary infection – causes chicken pox – prodrome of fever and malaise followed by development of widespread vesicular rash. Usually lasts ~2 weeks and then becomes latent. Can reactivate in shingles.
Treatment: vaccine is available and anti-viral medication can be give
What is herpes zoster/shingles?
When can there be serious consequences?
Herpes Zoster or Shingles where there is reactivation of the VZV and a painful vesicular rash appears along the course of a dermatome – usually heals in 2-4 weeks.
- There can be serious consequences if CN V1 (ophthalmic division of trigeminal).
What are the features and pathogenesis of trichophytum?
What is its treatment?
Trichophytum – e.g. Trichophytum rubrum
Features of Trichophytum:
- o A common cause of superficial fungal infections.
- o It is a dermatophyte – a type of fungus that particularly affects parts of the body that have keratin.
- o The names of the clinical infections are prefixed with the Latin “tinea” followed by the body part:
- Tinea capitis – Kerion is a type of tinea capitis.
- Tinea manuum – dorsum of hand.
Yeasts are another form of fungal infection distinct from dermatophytes – e.g. candida (grow in warm/wet places).
Pathogenesis:
- o Clinical manifestations – eryhthromatous scaly rash on skin/scalp, discoloured or crumbly nails.
Treatment: with topical or systemic anti-fungal medications such as Terbinafin
What are the features and pathogenesis of scabies?
How is it transmitted and what is its treatment?
Features:
- o A skin infestation by the mite Sarcoptes scabei.
Pathogenesis:
- o The mite burrows into the surface of the skin and exposure to the mite faeces and eggs cause a delayed-type allergic reaction resulting in widespread eczematous rash occurring ~4 weeks after first infestation.
- o Usually very itchy.
- o The burrow sites are usually at – genital regions, nipples, wrists, finger webs, instep of feet, axilla.
- o Secondary bacterial infection is common.
Transmission: by skin-skin contact.
Treatment: with topical systemic insecticides.
