What is impetigo?
A superficial, contagious, blistering infection of the skin caused by the bacteria Staphylococcus aureus and Streptococcus pyogene
What are the different types of impetigo?
- Bullous
- Non-bullous
What is the most common form of impetigo?
Non-bullous impetigo - 70% of cases
What layer of the skin does impetigo affect?
Epidermis
What is bullous impetigo caused by?
Staphylococcus - produces exfoliative toxin
How do bullae form in impetigo?
Toxin that contains serine proteases acting on desmoglein 1. This process allows S. aureus to spread under the s.corneum in the space formed by the toxin, causing the epidermis to split just below the stratum granulosum.
Large blisters then form in the epidermis with neutrophil and, often, bacterial migration into the bullous cavity. In bullous impetigo, the bullae rupture quickly, causing superficial erosion and a yellow crust
What are the main causative agents of impetigo?
- Staphylococcus
- Group A B-haemolytic strep
What causes non-bullous impetigo?
Streptococcus pyogenes
What is the following?
Impetigo
What might you see on examination in someone with impetigo?
Erosions that have a yellowish to golden crust on an erythematous base, with patchy distribution, often in the peri-oral and peri-nasal area, although they can occur anywhere on the body.
How would you manage someone with impetigo?
Topical antibiotics
- Fusidic acid
- Flucloxacillin
Hygeine advice
What is erysipelas?
A distinct form of superficial cellulitis with notable lymphatic involvement and is raised, sharply demarcating it from uninvolved skin
What layer of the skin does erysipelas affect?
Dermis
What is the cause of erysipelas?
Strep. pyogenes
What are features of erysipelas?
- Painful, red area
- Fever
- Regional lymphadenopathy and lymphangitis
- Distinct elevated borders
What is the following?
Erysipelas
Where does erysipelas most commonly affect?
The face
How would you treat erysipelas?
Benzylpenicillin + Flucloxacillin - consider IV if serious
What is cellulitis?
An acute spreading infection of the skin with visually indistinct borders that principally involves the dermis and subcutaneous tissue
What layers does cellulitis affect?
Dermis and subcut tissue
What organisms are implicated in cellulitis?
- B-haemolytic streps
- Staph. aureus
What are signs of a cellulitis?
- Pain
- Swelling
- Warmth
- Erythema - no distinct borders
- Systemic upset plus fever
- Lymphadenopathy/lymphangitis
Where does cellulitis most commonly affect?
Lower legs
What is the following?
Ascending lymphangitis
What is the following?
Cellulitis
How would you treat a mild cellulitis empirically?
Oral Flucloxacillin or clarythromycin - 7-14 days
How would you treat moderate to severe cellulitis?
IV Flucloxacillin, switch to oral fluclox/doxycycline
What is folliculitis?
Pustular infection of a single hair follicle which can occur in clusters typically on head, back buttocks and extremities
What is the cause of folliclitis?
S. Aureus
What are the features of folliculitis?
- Circumscribed, pustular infection of a hair follicle
- Up to 5mm in diameter
- Present as small red papules - Central area of purulence that may rupture and drain
Where is folliculitis typically found?
Head, back, buttocks and extremities
What is furunculosis?
An inflammatory infection of a single hair follicle that extends deep into dermis and subcutaneous tissue. Usually affecting moist hairy areas of body
What is the most common cause of furunculosis?
S. aureus
What are features of furunculosis?
- Single hair follicle-associated inflammatory nodule
- Extending into dermis and subcutaneous tissue
- May spontaneously drain purulent material
What are risk factors for folliculitis?
- Obesity
- Diabetes mellitus
- Atopic dermatitis
- Chronic kidney disease
- Corticosteroid use
What are carbuncles?
Large abscess involving multiple adjacent hair follicles, which tend to by multiseptated. These may drain spontaneously
What are features of carbuncles?
Infection extends to involve multiple furuncles
- Multiseptated abscesses
- Purulent material expressed from multiple sites
Where are carbuncles most commonly found?
- Back of neck
- Posterior trunk
- Thigh
How would you treat folliculitis?
Topical antibiotics
How would you treat a furuncle?
Topical/oral antibiotics
How would you manage someone with a carbuncle?
Hospital admission, surgery and IV Abx
What is necrotising fasciitis?
A life-threatening subcutaneous soft-tissue infection that may extend to the deep fascia, but not into the underlying muscle. The causal organisms may be aerobic, anaerobic, or mixed flora
What are the main clinical forms of necrotising fasciitis?
- Type I - polymicrobial
- Type II - monomicrobial infection with Streptococcus pyogenes (group A streptococci)
What organisms are commonly involved in type I necrotising fasciititis?
An aerobe and a facultative anaerobe
- Streptococci
- Staphylococci
- Enterococci
- Gram negative bacilli
- Clostridium
What are the majority of superificial skin infections caused by?
- S. aureus
- S. pyogenes
What layers are involved in necrotizing fasciitis?
Infection extends through the fascia but not into the underlying muscle, and tracks along fascial planes extending beyond the area of overlying cellulitis
What are symptoms of necrotizing fasciitis?
Rapid onset, sequential development of:
- Severe, unremitting pain around site
- Fever
- Delerium
What are signs of necrotising fasciiitis?
- Crepitus
- Haemorrhagic bullae
- Skin necrosis
- Anaesthesia at site of infection
How would you diagnose necrotising fasciitis?
Clinical diagnosis
How would you manage someone with necrotizing fasciitis?
- ABx - Fluclox + benpen + Gentamicin + Clindamycin
- Urgent surgical debridement +/- amputation
What is the overall mortality associated with necrotising fasciitis?
17-40%
What would you trat GAS necrotizing fasciitis?
Benzylpenicillin and clindamycin
What is pyomyositis?
A bacterial infection of the skeletal muscles which results in a pus-filled abscess. Pyomyositis is most common in tropical areas but can also occur in temperate zones.
Where does pyomyositis most commonly occur?
- Thigh
- Calf
- Arms
- Gluteal region
- Chest wall
- Psoas muscle
What are predisposing factors to the development of pyomyositis?
- Diabetes mellitus
- HIV/immunocompromised
- Intravenous drug use
- Rheumatological diseases
- Malignancy
- Liver cirrhosis
What are features of pyomyositis?
- Fever
- Pain
- Woody induration of affected muscle
How would you investigate suspectedd pyomyositis?
- Clinical diagnosis
- Imaging - CT/MRI
How would you manage someone with pyomyositis?
- Drainage
- Antibiotics
Where are features of septic bursitis?
- Fever
- Pain on movement
- Peribursal cellulitis
- Swelling
- Warmth
How would you investigate someone with septic arthritis?
- Clinical diagnosis
- Fluid aspiration
What is infective tenosynovitis?
Infection of the synovial sheats that surround tendons
What are organisms implicated in infective tenosynovitis?
- S. aureus
- Strep
- Mycobacteria
- Fungi
What are features of infective tenosynovitis?
- Erythematous fusiform swelling of finger
- Pain with extension of finger
- Held in a semiflexed position
- Tenderness over the length of the tendon sheath
How would you manage someone with infective tenosynovitis?
- Abx
- Hand surgeon referral
What is staphylococcal scalded sking syndrome?
An illness characterised by red blistering skin that looks like a burn or scald, hence its name staphylococcal scalded skin syndrome.
The scalded skin syndrome is caused by a toxin-secreting strain of S. aureus.
What toxin is implicated in SSSS?
Exfoliatin - causes intra-epidermal cleavage at the level of the stratum corneum leading to the formation of large flaccid blisters that shear readily.
Who does SSSS most commonly affect?
Children under the age of 5
How would you treat staph scalded skin syndrome?
IV fluids and flucloxacillin
What is toxic shock syndrome?
A condition of shock caused by bacterial super antigens
What organisms cause toxic shock syndrome?
- Staphylococcus
- Streptococcus
What toxin is implicated in TSS?
TSST-1 - causes cytokine release with abrupt onset of fever and shock, with a diffuse macular rash and desquamation of the palms and soles
What are features of TSS?
- Shock
- Confusion
- Fever
- Rash
- Diarrhoea
- Myalgia
- Desquamation of hands and feet
What can be a cause of TSS in females?
Indwelling tampon
What is a class I surgical wound?
Clean wound (respiratory, alimentary, genital or infected urinary systems not entered)
What is a class II surgical wound?
Clean-contaminated wound (above tracts entered but no unusual contamination)
What is a class III surgical wound?
Contaminated wound (Open, fresh accidental wounds or gross spillage from the gastrointestinal tract)
What is a class IV surgical wound?
Infected wound (existing clinical infection, infection present before the operation)
What is MRSA?
Methicillin-resistnat staphylococcus aureus
Where is MRSA most commonly acquired?
Hospital acquired infection
What is MRSA resistant to?
Resistant to penicillin and isolated resistance to other β-lactam antibiotics such as meticillin (now rarely used) and flucloxacillin
What is MRSA most commonly found in?
Surgical wounds
What antibiotics would you use for MRSA infection?
- Vancomycin
- Linezolid
- Teicoplanin
- Daptomycin