Dermatological and ENT Microbiology Flashcards
What is Necrotising Fasciitis?
Necrotising Fasciitis is a severe skin disease in which bacteria release toxins that damage the fascia underneath the skin, including the muscle and bone, which can lead to skin necrosis.
MEDICAL EMERGENCY AS IT CAN KILL OVERNIGHT
What bacteria cause Necrotising Fasciitis?
Staph. Aureus
Strep. Pyogenes (Group A) - most common cause
Coliforms and Anaerobes
What are the 2 Types of Necrotising Fasciitis?
Type 1 - caused by Coliforms and Anaerobes
Type 2 - caused by Strep. Pyogenes (Group A)
List symptoms of Necrotising Fasciitis
Patient is in excruciating pain despite there being no obvious deformity e.g. scarring/wounds.
Crepitations heard from skin due to gas build-up underneath (air seen under the skin on imaging)
Skin feels like bubble wrap on squeezing
Inflammatory Signs e.g. Redness, swelling, hot
Explain management for necrotising fasciitis
Surgical Debridement of dead skin, pus and foreign bodies is curative!
Samples can be taken from the debrided dead skin for targeting antibiotics (given for 6-8 weeks)
Are antibiotics curative in Necrotising Fasciitis?
NO.
They simply aid in recovery.
What is the difference between Impetigo and Cellulitis?
Impetigo is localised to the face and is therefore, spread via Facial Discharge.
Cellulitis can occur anywhere on the body and is a more general term.
Moreover, Impetigo is superficial whereas Cellulitis can involve the Dermis.
Which bacteria most commonly cause impetigo?
Staph. Aureus
Strep. Pyogenes (Group A)
Is Cellulitis associated with Necrosis?
No.
Who does Impetigo most commonly occur in?
Children
What antibiotics are used in Cellulitis treatment?
Flucloxacillin for Staph. Aureus
Benzylpenicillin (Penicillin G) for Strep. Pyogenes
What is a Toxinosis?
Infections caused by Toxins released by the bacteria
What is Toxic Shock Syndrome (TSS)?
Infection caused by toxin release from Staph. Aureus which results in the surrounding host tissue being attacked
What are the 2 types of TSS?
Menstrual TSS
Non-Menstrual TSS
What happens in Menstrual TSS?
Staph. Aureus releases TSST-1 which diffuses through the vaginal wall causing the surrounding host tissue to be attacked by the host immune system
Biggest risk factor for this is Tampon Use
What happens in Non-Menstrual TSS?
Staph. Aureus releases SEB and SEC exotoxins which diffuse through the host tissues causing the surrounding host tissue to be attacked by the host immune system
What condition similar to TSS is caused by Strep. Pyogenes?
Toxic Shock-LIKE Syndrome (TSLS)
What happens in TSLS?
Bacteriophage 12 causes the normally harmless Strep. Pyogenes to change into a harmless form, which in turn releases exotoxins causing the surrounding host tissue to be attacked by the host immune system
What is the differentiating clinical sign for TSS and TSLS?
TSS is localised
TSLS is more invasive
What is the diagnostic criteria for TSS and TSLS?
Fever
Hypotension
>3 Organ Systems involved
Macular Rash and Desquamation
What are conditions caused by Staph. Aureus (including MRSA)?
Recurrent Furunculosis
Necrotising Pneumonia
Scalded Skin Syndrome (SSS)
What happens in Recurrent Furunculosis?
Staph. Aureus infection of the hair follicles causing abscess, pus and necrotic tissue formation.
It is defined as 3 or more attacks within a 12 month period.
What happens in Necrotising Pneumonia?
Staph. Aureus infection in the lungs which enter the blood and inner tissues, releasing PVL which attacks the immune system.
List symptoms of Necrotising Pneumonia
Acute Respiratory Distress
Hypoxaemia
Deteriorating Lung Function
Multi-Organ Failure DESPITE ANTIBIOTICS
Antibiotics do not help much - patients tend to die after 10-12 days
What happens in SSS?
Staph. Aureus releases toxins which target Desmoglein-1 in the Corneodesmosomes between the Corneocytes of the Keratin Layer, causing cleavage resulting in a build-up of residue and excess exfoliation of the skin
Where does SSS typically arise?
Groin, Axillae and Face
What is the most common cause of Fungal Skin Infections?
Ringworm (Tinea)
What fungus causes Athlete’s Foot?
Tinea Pedis (Ringworm of the Foot)