4. Skin infections Flashcards
Is Staph. aureus G+ or G-?
G+
Where is Staph. aureus most commonly found on the body?
In the nostrils or skin (commensal bacteria)
What is panton valentine leucodin?
- Toxin produced by S. aureus
- Virulence factor
- Leads to a necrotising infection
What is exfoliative toxin?
- Toxin produced by S. aureus
- Cleaves the epidermis
- Blistering
What is TSST-1?
- Toxic shock syndrom toxin 1
- Produced by S. aureus
- Causes sickness, fever, malaise => organ failure
- Related to tampons
What do we see if the S. aureus infection is within the top layer of the skin (stratum corneum)?
Impetigo
What is a ‘boil’ and ‘carbuncle’?
Boil - abscess of the hair follicle
Carbuncle - abscess of several adjacent follicles
What is a deep (full thickness involvement of epidermis) form of impetigo called?
Ecthyma • firmly adherent crust • won't come off • surface of skin is dying • common after infected insect bites
What is infection and inflammation of a hair follicle called?
Folliculitis
Describe impetigo
- S. aureus infection on surface of epidermis
- Honey-coloured crust on eroded base
- Mainly occurs around the nose and mouth
- Blisters can be easily broken and cause erosions
What is bullous impetigo?
S. aureus is making the exfoliative toxin on the surface of the epidermis
Local infection
What is Staphylococcal scaled skin syndrome?
- Condition caused by the exfoliative toxin
- Toxin has entered from skin into blood
- Toxin is also causing cleavage of the epidermis distant to the origin of the infection (desquamation of the epidermis)
- Systemic infection
- Mucous membranes not affected
Who does Staphylococcal scaled skin syndrome affect and how do we treat it?
- Children under age of 5 - related to immature immune system
- Treat with antibiotics and emollients
What is toxic epidermal necrolysis?
- Widespread desquamation of the skin
- Mucous membranes are affected
- Result of an allergic reaction to a drug
What does Staphylococcal scaled skin syndrome affect?
Only the skin
What is Treponema Pallidum and what does it increase the transmission of?
- Gram negative spirochete
- Cause of Syphilis
- Increases transmission of HIV
Describe the 3 phases of syphilis
1) Primary (3-8 weeks)
• Painless ulcer (chancre) at inoculation site (genital or oral)
• Lasts a few weeks then heals
2) Secondary (6-12 weeks)
• Disseminated infection, generalised rash and lymphadenopathy
• Warty lesions around perineum, axillae and groins
• Gets better and enters latent phase
• Patient can be asymptomatic for several years but can lead to tertiary syphilis without treatment
3) Tertiary syphilis (years later)
• Skin, neurological and vascular manifestations
• e.g. dementia, depression, dilatations of thoracic aorta
What is congenital syphilis?
- Acquired perinatally (trans-placental transmission from mother with latent syphilis)
- Early and late manifestations
- Most of these babies die before or prematurely after birth
- Skin ulcers, bony defects, saddle nose, blindness etc.
- All pregnant mothers are screened
What are gummatous skin lesions?
- Caused by syphilis, but very rare now
- Ulcerating lesions of the skin
- Often with destruction around the oro-nasal region
How do we treat syphilis?
Penicillin antibiotics
What are the 4 most important human herpes viruses and what do they cause?
- HHV-1 (HSV-1) - cold sores
- HHV-2 (HSV-2) - genital warts
- HHV-3 (varicella zoster) - chicken pox / shingles
- HHV-4 (EBV) - infectious mononucleosis (glandular fever)
What does HHV-8 cause?
Kaposi Sarcoma - cancer in endothelial cells and lymphatics
Which herpes viruses show latency?
All viruses
What are the 3 types of clinical presentations of the herpes simplex virus (1/2)?
- Vesicular rash (2 weeks)
- Eczema herpeticum
- Herpes encephalitis
