Skin infections Flashcards
Skin infections are more common where?
Hot humid conditions and poor populations
Two important characteristics of staphylococcus aureus bacteria
gram positive
commensal
(= most common bacterial cause of skin infections)
List the toxins produced by SA and the diseases/problems caused by each of this toxins
Panton Valentine Leuocidin => Necrotising soft tissue infections
Exfoliative toxin => Staphylococcal Scalded Skin Syndrome
TSST-1 (Toxic Shock Syndrome Toxin 1) => Toxic shock Syndrome
Enterotoxin => diarrhoea (food poisoning)
State and describe the different manifestations of S. Aureus skin infections
Impetigo (and bullous/blistering impetigo) = infection of sub corneal layer of epidermis; looks like golden crusty skin
Folliculitis = infection mouth of hair follicle
Ecthyma = infection of full thickness of epidermis
Boil = abscess of hair follicle Carbuncle = abscess of several adjacent hair follicles
Treatment of SA infections?
Antibiotics
What kind of bacterium is Treponema pallidum?
Gram negative spirochaete
What disease is caused by Treponema pallidum?
Syphilis (=Sexually Transmited Disease)
Describe the staging of syphilis
Primary (at 3-8 weeks):
- Painless ulcer (aka chancre) at inoculation site (Genital or oral)
Secondary (at 6-12 weeks):
- Disseminated infection
- Generalised maculopapular rash and lymphadenopathy
- Condyloma lata
Latent syphilis (no clinical signs)
Tertiary syphilis (usually years later): - Skin, neurological and vascular manifestations e.g. bone lesions, gummatous lesions, thoracic aneurysm
How is congenital syphilis acquired?
Acquired perinatally
Human Herpes Viruses are what kind of viruses?
DNA viruses
Type 1 and Type 2 HSV causes infections where? State the target cell?
Type 1 – causes oral infections.
Type 2 – causes genital infections.
Muco-epithelial cell
HSV - Site of latency? State the significance.
Neuron
- there can be reactivation with reoccurrences of infection.
How is HSV transmitted? List the clinical features.
Transmission by direct contact.
Clinical features:
- painful vesicular rash (heals over 2-4 weeks)
- eczema herpeticum
- herpes encephalitis
State another name for Human Herpes Virus-3
Varicella Zoster Virus
What deceases does VZV cause?
Chicken pox (primary infection) Shingles
Describe the pathogenesis of 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.
What appears on the skin in the reactivation of the VZV infection as shingles? When might 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.
There can be serious eye consequences if the distribution of the Ophthalmic Division of the Trigeminal nerve is involved.
Trichophytum:
- Most common cause of what kind of fungal infection?
- What type of fungi is it?
- Particularly infects what?
- Describe the method of naming of clinical infections?
- This is a common cause of superficial fungal infections.
- It is a dermatophyte.
- Particularly infects parts of the body which have keratin, ie skin, nails and hair.
The names of clinical infections have the prefix ‘tinea’ then the Latin body part involved, eg tinea capitis, tinea manuum etc.
Give an example of a common species of trichophytum.
What are the clinical manifestations of an infection from this species?
Treatment?
Trichophytum rubrum
The clinical manifestations:
- erythematous scaly rash on skin/scalp
- discoloured and crumbly nails.
These infections can be treated with topical or systemic antifungal medication such as Terbinafinew
What is Scabies?
This is a skin infestation with the mite Sarcoptes Scabei.
What does the mite do?
The mite burrows in the surface of the skin.
Exposure to mite faeces and eggs causes what?
Exposure to mite faeces and eggs causes a delayed allergic reaction which results in a wide spread itchy eczematous rash
Scabetic burrows can be found where on the body?
Burrows can be found in certain regions of the body e.g. genital region, nipples, wrists, finger webs, instep of the feet, axillae.
What is common as a secondary manifestation of the scabetic burrows?
Secondary bacterial infection is common.
