Infections of the Skin

Question 1

What is Acne?

Answer 1

• Subcutaneous skin infections
• Causing spots, painful hot skin
• Caused by Proprionibacterium acnes
• Pathogenesis;
  The bacteria digest sebum which attracts neutrophils and local pro-inflammatory markers.
  The neutrophils release digestive enzymes which create lesions ‘pus pockets’
• Treat only severe cases
• Common during puberty and shortly after (11-30 year olds)
• Can lead to scarring and depression –> possible folliculitis

Question 2

What are Carbuncles/Furnacles

Answer 2

• Deep necrotising form of folliculitis
• Caused typically by Staph. aureus (especially MRSA)
• Caused when the bacteria colonise and invade hair follicles through a wound causing tender, erythematous, perifollicular nodules
• Treatment via antibiotics

Question 3

What is Cellulitis?

Answer 3

• Infection of the skin caused by the normal flora invading and colonising the deeper layer of the skin through abrasion.
• Typically caused by staphylococci and streptococci

Question 4

What is Tetanus?

Answer 4

• Infection caused by Clostridium tetani
• Symptoms include; spasms, paralysis
• Bacterial reservoir typically in soil
• Typically caused when bacteria invade and colonise through a wound. The bacteria releases an endotoxin known as Tetanospasmin, which travels through peripheral motor neurones. Blocks GABA at motor neurones causing hyperexcitability - leading to seizures and contractions
• Can lead to broken bones and respiratory arrest
• Treatment via antibiotics, anti-toxin, and muscle relaxants, GABA agonist
• Prevention via vaccine DTaP

Question 5

What is Toxic Shock Syndrome?

What happens in regards to the cardiovascular system?

Answer 5

• Type of Septic Shock
• Caused typically by streptococci & staphylococci & multiple other bacterium
• Symptoms; Fever, low BP, Confusion, Malaise
• Pathogenesis; Superantigen exotoxin is produced which binds to MHC II on T-Cell receptors –> leading to polyclonal T-Cell activation –> Overexaggerated immune response leading to a release of large amount of cytokines.
• Treatment via Sepsis 6. Resect any necrotic tissue
• (Can be caused by use of very absorbent tampons)

Cardiovascular system:
Toxin –> Vasodilation (decreased TPR), decreased arterial pressure, impaired perfusion of vital organs.
Capillaries are leaky hence blood volume and venous pressure decrease
The fall in arterial pressure is detected and cardiac output increased.

Question 6

Etiology of Herpes Simplex Virus (Labialis, Gladiatorm and Herpes Zoster)

Answer 6

• Highly contagious and is usually transmitted directly through a lesion in the skin or mucous membrane
• Resides in sensory nerve, neurilemmal sheath following initial outbreak
• Recurrent attacks stimulated by sunlight, emotional disturbances, illness, fatigue or infection,
  Type I vs Type II (HSV Type I - Genital sores, HSV II - Cold sores)

Question 7

What is Necrotising Fascitis?

Answer 7

• Caused by streptococci, staphylococci, MRSA
• Symptoms: RUBOR, TUMOR, DOLOR, CALOR - fever, develops bullae
• Subcutaneous bacteria invade and colonise deeper layers of the skin
• Bacteria invade deep and superficial fascia by releasing toxins and digestive enzymes.
• Infection leads to vascular necrosis, ischaemia,
• Superficial nerves are damaged.
• Can lead to septicaemia
• Treatment with antibiotics, resection of necrotic tissue