BACTERIAL SKIN INFECTIONS

Question 1

What is erysipelas?

Answer 1

A localised skin infection caused by streptococcus pyogenes
In simple terms it is a more superficial, limited version of cellulitis
It affects the dermis and upper subcutaneous tissue only

Question 2

Clinical features of erysipelas?

Answer 2

Sharply defined borders of raised, swollen, firm, erythematous skin
Commonly affects the lower limbs but can cause a “butterfly” distribution on the face

Question 3

What causes erysipelas?

Answer 3

Almost all are caused by group A beta-haemolytic streptococci

Question 4

Treatment of erysipelas?

Answer 4

Flucloxacillin

Question 5

What is cellulitis?

Answer 5

A bacterial infection of the dermis and deeper subcutaneous tissues

Question 6

What causes cellulitis most commonly?

Answer 6

Streptococcus pyogenes
Less commonly - staph aureus

Question 7

Clinical features of cellulitis?

Answer 7

Unilateral usually. Most commonly on shins
Erythema
Swelling
Systemic upset - fever, malaise, nausea
Blisters and Bullae may be seen with more severe disease

Question 8

Diagnosis of cellulitis?

Answer 8

Clinical - no further investigations required
Bloods and cultures only if septicaemia is suspected

Question 9

What classification do we use to guide how we manage pt with cellulitis?

Answer 9

The Eron classification

Question 10

Outline the Eron classification?

Answer 10

Class 1 - no signs of systemic toxicity and pt has no uncontrolled comorbities
Class 2 - pt is systemically unwell or has a co-morbidity which may complicate/delay resolution of infection
Class 3 - significant systemic upset or unstable co-morbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromise
Class 4 - sepsis syndrome or a severe life-threatening infection e.g. necrotising fasciitis

Question 11

Which patients with cellulitis should be admitted to hopsital for IV antibiotics?

Answer 11

Eron Class 3 or 4 cellulitis
Severe or rapidly deteriorating cellulitis
<1 or frail
Immunocomprosed
Significant lymphoedema
Facial cellulitis or periorbital cellulitis

Question 12

Management of Eron Class 1 cellulitis?

Answer 12

Antibiotics - oral Flucloxacillin as first-line Tx

Question 13

Management of Eron Class 2 cellulitis?

Answer 13

Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines

Question 14

Management of Eron Class 3-4 cellulitis?

Answer 14

Admit
NICE recommend oral/IV co-amoxiclav, clindamycin, cefuroxime, ceftriaxone

Question 15

Risk factors for erysipelas or cellulitis?

Answer 15

Previous infection
Venous insufficiency
Immunodeficiency
Breaks in skin barrier - bites, ulcers, psoriasis, eczema
Obesity
Fissured toes/heels due to athletes foot

Question 16

What is impetigo?

Answer 16

A superficial bacterial skin infection that can be a primary infection or a complication of an existing skin condition such as eczema, scabies or insect bites
It’s common in children, particuarly during warm weather

Question 17

What typically causes impetigo?

Answer 17

Staph aureus or streptococcus pyogenes

Question 18

Where does impetigo typically occur on the body?

Answer 18

On the face, flexure and limbs not covered by clothing

Question 19

How is impetigo spread?

Answer 19

By direct contact with discharges from the scabs of an infected person
The bacteria invade the skin through minor abrasions and then spread to other sites by scratching

Question 20

How does impetigo present?

Answer 20

Erythematous macule that vesiculates or pustulates
Characteristic golden crust

Question 21

Management of limited, localised impetigo?

Answer 21

Hydrogen peroxide 1% cream
Other options - topical fusidic acid, topical mupirocin

Question 22

Management of extensive impetigo?

Answer 22

Oral flucloxacillin or oral erythromycin if penicillin-allergic

Question 23

School exclusion for impetigo?

Answer 23

children should be excluded from school until the lesions are crusted and healed or 48 hours after commencing antibiotic treatment

Question 24

What is Folliculitis?

Answer 24

An inflammatory condition of the hair follicles, typically presenting as papules or pustules
Occurs anywhere on the body but the palms and soles are usually exempt

Question 25

Aetiology of Folliculitis?

Answer 25

Folliculitis can be caused by various factors, predominantly bacterial infections, specifically Staphylococcus aureus. It can also result from Gram-negative organisms, often following long-term antibiotic therapy for conditions like acne.

A particular form, eosinophilic folliculitis, is sterile and most commonly arises in the context of immunosuppression, like in HIV patients. The causative factor in this case is not an infection but a reactive condition associated with the immune status.

Question 26

Presentation of Folliculitis?

Answer 26

Papules and pustules
You may see a hair coming out of these bumps
The affected skin can feel painful, hot and may be itchy

Question 27

What is hot tub folliuclitis?

Answer 27

Folliculitis caused by an infection with pseudomonas aeruginosa from improperly santisided hot tubs or spas

Question 28

Management of folliucltiies?

Answer 28

Mild cases dont need treatment and will clear within 7-10 days
Antibacterial soaps can be used
Fusidic acid can be used for localised areas
Oral antibiotics may be needed if folliuclities is severe or widespread

Question 29

What is a furuncle?

Answer 29

A boil - a painful, pus-filled bump that forms under your skin when bacteria infect a hair follicle
They usually start as a red/purple tender bump which quickly fills with pus growing larger and more painful until they rupture and drain. They develop a yellow-white tip

Question 30

What is a carbuncle?

Answer 30

A cluster of boils that form a connected area of infection

Question 31

What are the 2 types of necrotising fasciitis?

Answer 31

Type 1 : caused by mixed anaerobes and aerobes - most common
Type 2 : strep pyogenes

Question 32

Who does type 1 necrotising fasciitis most commonly occur in?

Answer 32

Diabetics post-surgery

Question 33

Risk factors for necrotising fasciitis?

Answer 33

Recent skin trauma, burns or soft tissue infections
Diabetes mellitus, particularly if Tx with SGLT2 inhibitors
IV drug users
Immunosuppression

Question 34

Most commonly affected site for necrotising fasciitis?

Answer 34

The perineum - known as fournier’s gangrene

Question 35

What’s is necrotising fasciitis?

Answer 35

A severe, life-threatening infection characterised by rapidly progressing inflammation and necrosis of the fascia and subcutaneous tissue
It spreads along fascial planes, but typically spares the underlying muscle

Question 36

Features of necrotising fasciitis?

Answer 36

Acute onset pain, swelling and erythema at the affected site
Often presents with rapidly worsening cellulitis with pain out of keeping with physical features
It’s extremely tender with hypoaesthesia to light touch
Skin necrosis, crepitus and gas gangrene are late signs
Fever and tachycardia may occur

Pain is disproportionate to clinical signs

Question 37

Management of necrotising fasciitis?

Answer 37

Urgent surgical referral debridement
IV antibiotics

Question 38

Prognosis of necrotising fasciitis?

Answer 38

Average mortality of 20%

Question 39

What is staphylococcal scalded skin syndrome?

Answer 39

A rare, severe, superficial blistering skin disorder characterised by detachment of the epidermis - triggered by exotoxins release from staph aureus strains

Question 40

Who gets staphylococcal scalded skin syndrome?

Answer 40

Predominantly in children younger than 5
Peak age 2-3