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)
What is Trichophyton Rubrum?
Fungal Worm (Type of Fungus: Dermatophyte)
How does Trichophyton Rubrum infection occur?
Trichophyton Rubrum enters abraded/soggy skin and spreads out its fungal branches (hyphae) in the Keratin Layer.
Can only infect keratinised tissues e.g. Skin, Hair and Nails
List symptoms of Trichophyton Rubrum infection
Scaling due to increased fungal turnover
If acute: Red Patches
If chronic: Ringed Lesions (lesion heals in centre but continues to grow outwards)
How are Dermatophyte Infections diagnosed?
Wood Light
Clinical Appearance
How is Dermatophyte infection of the skin OR nails treated?
Canesten (Clotrimazole) Cream
Amorolfine Topical Nail Varnish
How is Dermatophyte infection found on the skin, hair (scalp) AND nails treated?
Oral Terbinafine
Oral Itraconazole
What virus causes Chicken Pox and Shingles?
Varicella Zoster Virus (VZV)
Chicken Pox a.k.a. Varicella
Shingles a.k.a. Herpes Zoster
What is the differences between Chicken Pox and Shingles?
Chicken Pox occurs on primary exposure to VZV
List symptoms of Chicken Pox
Generalised Rash (starts off macular, then becomes papular, then vesicular, skin scabs over and finally recovers)
Intense itch
Fever
Possible scarring
How is Chicken Pox diagnosed?
On history alone if it is strongly indicative.
Viral swabs are taken in cases of doubt.
How does Shingles occur?
Once infected with Chicken Pox, the VZV NEVER leaves the body. Instead, it becomes dormant and hides away in the Dorsal Root Ganglia.
On spontaneous reactivation, it results in Shingles.
What is the give-away sign of Shingles?
Rash localised along a single dermatome, appearing no where else in the body
Describe the classic history of Shingles
Neuralgic/Tingling pain in the soon-to-be-affected dermatome.
Erythematic rash follows.
Rash develops vesicles and crusting
What is Trigeminal Shingles?
When VZV reactivates in the Trigeminal Nerve.
In Ophthalmic Zoster, involve the Ophthalmologist as there is a high chance of eye damage.
How is the VZV Vaccine useful for Shingles?
Reduces the impact of Shingles if reactivation occurs.
What is Ramsay-Hunt Syndrome?
This is when VZV reactivates in the Facial Nerve, causing Facial Nerve Shingles
Generally more associated with Herpes Simplex rather than Herpes Zoster
List consequences of Ramsay-Hunt Syndrome?
Facial Nerve Palsy
Deafness, Vertigo and Tinnitus
Vesicles and Pain in the Auditory Canal and Throat
Ear consequences occur due to irritation of CN VIII
What is Herpes Simplex?
Primary Gingivomatitis
How is Herpes Simplex spread?
Saliva exposure e.g. Kissing
Is Herpes Simplex recurrent?
Yes, it can become dormant and reactivate in later life causing:
Cold Sores
Genital Herpes
What are the 2 Types of Herpes Simplex virus?
Type 1 - main cause of cold sores and 50% of genital herpes. Rare cause of Encephalitis
Type 2 - rare cause of cold sores but 50% of genital herpes. Can cause Encephalitis/Disseminated Infection in neonates.
Where can Recurrent Herpes Simplex spread to?
Herpetic Whitlow - spread of herpes simplex to fingers from touching cold sores on mouth
Eczema Heperticum - spread of herpes simplex throughout eczema lesions on body. Widespread outbreak which is life-threatening
How is VZV and Herpes Simplex treated?
Acyclovir
ONLY TARGETS ACTIVE DISEASE, NOT LATENT DISEASE
What is Erythema Multiforme and how is it caused?
Autoimmune lesions which are induced by either; medications or infection e.g. Herpes Simplex or Mycoplasma bacteria.
Are warts and verrucae the same thing?
Yes, verrucae are simply feet warts that look different as they become squashed from weight load.
How are warts treated?
Burned off with Topical Salicylic Acid
Which viruses are known for causing warts?
HPV Types 1-4
Types 6 and 11 cause Genital Warts
List conditions caused by Enterovirus (particularly the Coxsackie Enterovirus)
Herpangina
Hand, Foot and Mouth Disease
What are symptoms of Herpangina?
Gingivostomatitis
Vesicles on the Soft Palate which are so painful, people do not want to eat
What are symptoms of Hand, Foot and Mouth Disease?
Gingivostomatitis
Blisters on the hand, foot and mouth!
How are the Enteroviruses detected?
Viral Swab and PCR
What is Erythema Infectiosum?
A.k.a. Slapped Cheek Disease
Parvovirus B19 infection
What is the classic appearance of Slapped Cheek Disease?
Erythematic, raised rash on one cheek, making the individual look like they have been slapped hard.
The facial rash then disappears and:
Wrist Arthritis follows
IN CHILDREN ONLY: widespread macular rash follows
List complications of Parvovirus B19
Chronic Anaemia in immunosuppressed patients
Foetal swelling in pregnant women as it passes onto the child (causes aplastic anaemia and congenital heart failure, leading to swelling)
Aplastic crisis as it can shorten RBC life span
What is Syphilis?
STI caused by Treponima Pallidrum
List the stages of syphilis
Primary Stage - painless ulcers (chancre) found on site of entry in sex i.e. mouth or genitals
Secondary Stage - florid red rash prominent on soles and palms with ‘snail-tracking’ lesions on genitals or inside of mouth
Tertiary Stage - CNS or Cardiovascular involvement
How is Syphilis diagnosed?
Antibody blood test or bacterial swab of chancre
How is Syphilis treated?
Penicillin Injections
MUST BE TREATED EARLY AS PRIMARY SYPHILIS CAN PROGRESS TO SECONDARY THEN TERTIARY, INCREASING IN SEVERITY
What bacteria cause Lyme Disease?
Spirochete bacteria i.e. Leptospira and Borrelia
What is the hallmark sign of Lyme Disease?
Erythema Migrans - rash which slowly spreads around the body
How is Lyme Disease diagnosed?
Antibody blood test, especially for late presentation
How is Lyme Disease treated?
Doxycycline/Amoxicllin
