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Bacterial Infections
Acne Vulgaris
This is a condition where there is increased sebum production due to increased androgens
– This causes excess keratin production which block follicles making comedones
-Anaerobic bacteria Propionibacterium acnes colonise plugs giving inflammation
Appearance
– Red spots with pustules on face, cheeks, neck and upper trunk
N.B. Can become disseminated around the body with fever, malaise.
– This is known as acne fulminans and needs to be treated in hospital.
Management:
– 1st line is single topical creams –> Benzoyl peroxide (antimicrobial action) or Vitamin A derivative
– If not successful –> try multiple topical agents together
– If still uncontrolled –> oral antibiotics – tetracyclines (unless pregnant or under 12, so use erythromycin)
– In women, can use combined oral contraceptive pill with oestrogen + anti-androgenic progestogen
– If uncontrolled –> refer to dermatology for oral isotretinoin (Vitamin A derivative)
– This is the most successful treatment but needs monitoring of LFTs, mood and must not get pregnant.
Bacterial Folliculitis
This is infection and inflammation of one of more hair follicles, which can occur anywhere except palms of hands and soles of feet.
Cause: Most common is Staphylococcus aureus
– Pseudomonas Aeruginosa –> causes hot-tub folliculitis usually after sitting in a hot tub that was not cleaned properly before use
Appearance
– Reddened, itchy skin with pustules located around the hair follicles Management
Management
– Topical antiseptic treatment –> then topical antibiotics (Mupirocin)
Impetigo
This is a superficial bacterial infection due to S aureus or S pyogenes
– It commonly affects children, usually in warmer months and affects the face
– It is very contagious, and spread is by direct contact during play, and also indirectly through contaminated clothing and other items
Appearance
– Most common type is non-bullous, giving pustules around the mouth
– These red pustules release exudate making a golden-brown crust.
– Apart from the visual lesions, it is quite asymptomatic (non-painful, non-itchy)
Management
– Children excluded from school until 2 days after starting antibiotics
– If localised –> 1st line is hydrogen peroxide cream or fusidic acid cream, if resistant then mupirocin
– If widespread –> Oral flucloxacillin
Cellulitis
This is used to describe inflammation of the deep dermis and subcutaneous tissue
– Usually due to Streptococcus pyogenes or Staphylococcus Aureus
Appearance
– Usually seen on lower limbs affecting one leg
– Gives acute onset red, tender swollen skin that rapidly spreads
– Can have associated systemic upset e.g. fever, nausea
– Usually non-purulent (S, pyogenes) or purulent if Staph. Aureus.
Management
– Graded by Eron Classification according to systemic upset
– If < class 2 (systemically well) ➔ oral flucloxacillin
– If class 3 or more, or <1-year-old, or facial cellulitis ➔ admit to hospital for IV antibiotics due to sepsis risk
N.B. Erysipelas is an acute infection, usually due to S. Pyogenes which is very similar
– But it is more superficial to cellulitis and the rash is more raised + well demarcated and also seen on the face
Preseptal Cellulitis
This is an infection of the soft tissues in front of the orbital septum (eyelid, skin)
– Can be caused by breaks in the skin around the eye allowing bacterial entry
– Patients usually have a history of sinusitis or URTI, most commonly with Gram positive bacteria S. Aureus, S. epidermidis and streptococci.
– Different to orbital cellulitis, which is infection of soft tissues behind the orbital septum, a much more serious infection and needs IV antibiotics
Symptoms
– Swelling, redness and pain in one eye
– Inflammation of the eyelids causes a partial/complete ptosis
– Systemic symptoms e.g. fever, malaise
– No loss of vision, proptosis (bulging of the eye), ophthalmoplegia (suggests orbital cellulitis)
Tests – If any suspicion of orbital cellulitis, need CT contrast of the orbit
Management – Refer to hospital –> 1st line is co-amoxiclav (if untreated, can become orbital cellulitis)
Necrotising fasciitis
This is a bacterial infection of the subcutaneous tissue and fascia which covers muscles.
Bacteria release toxins which cause thrombosis of blood vessels.
– This leads to complete necrosis of the tissue and fascia.
– Type 1 –> Commonest type due to mixture of bacteria
– Usually seen in elderly patients with comorbidities (diabetes)
– Type 2 –> due to haemolytic group A Streptococcus e.g. S. Pyogenes
– Type 3 –> due to clostridium perfringens giving gas gangrene
Symptoms
– Development of a painful, red lesion within 24 hours of minor injury
– Usually seen on the limbs and perineum, giving a rapidly worsening cellulitis
– The pain is very severe, out of proportion to physical signs
– Lesion spreads almost like it is eating away the skin and can quickly lead to sepsis and toxic shock.
Management
– Admit to intensive care unit and IV antibiotics
– Surgical debridement ASAP to remove all necrotic tissue (usually repeated multiple times for a few days)
Viral Infections
Viral Warts (Verruca)
This is a HPV (human papilloma virus) infection of keratinocytes
Appearance
– Multiple skin coloured lesions, which have a warty appearance.
– Commonly found in hands and feet, which recur
Management
– Only treat is pain, functional disablement or cosmetic deformity
– 1st line is salicylic acid with paring and occlusion
– 2nd line is cryotherapy in combination with salicylic acid
Molluscum contagiosum
This is an infection which is due to the poxvirus Molluscum Contagiosum, seen in children aged younger than 10 who have a history of atopic dermatitis.
– It can also be widespread in immunosuppressed patients (e.g. HIV infection)
– Transmission occurs by direct close contact or contaminated surfaces
Appearance
– Clusters of round pink/white papules 1-6mm diameter.
– Have a shiny, waxy appearance with a central pit (umbilication)
– The papule has within it whitish matter
– Arises in warm, damp parts of the body like axilla, knee flexures and the groin – Do not arise on the palms of hands or sole of feet.
Management
– Self-limiting condition that usually resolves within 2 years
– Physical treatments –> squeezing lesions, cryotherapy (can leave white scars) or curettage
– Can lead to inflammation or secondary infection –> treat accordingly with steroid to topical antibiotic cream.
Fungal Infections
Dermatophytosis
This describes a superficial fungal infection which affects hair, skin or nails
3 main types of dermatophyte fungal infections categorised by part of body affected. – If unsure whether it is fungal, you can take fungal scrapings from the patient.
Causes: 90% due to mould Trichophyton rubrum, also due to Candida, Microsporum
i) Tinea capitis – An infection of the scalp commonly seen in children
– Can give dry scaling (like dandruff) and black dots (where hairs break off scalp) – Can gives an inflamed spongey mass called a kerion
Treatment – Oral terbinafine, griseofulvin or itraconazole
iii) Tinea corporis (Ringworm) – Gives well-defined annular red lesions with pustules
Treatment – Topical antifungal agents –> if unsuccessful oral itraconazole/terbinafin
ii) Tinea pedis (Athlete’s foot) – Gives itchy skin with peeling between toes – It is a very common condition and seen more in younger populations
Treatment – Topical terbinafine
Pityriasis Versicolor
This is a superficial fungal infection due to the yeast Malassezia furfur, which causes discoloured patches on the torso and the back.
– The hypopigmentation occurs due to a chemical that impairs melanocyte functioning
– It most often affects young adults and is seen more in hot humid climates
Appearance
– Hypopigmented, pink or brown patches usually on trunk
– The patches can start scaly but then resolve and become more white
– It is usually asymptomatic but can be a bit itchy
Management
– Topical antifungal (ketoconazole) –> switch to oral if topical fails
Parasitic Infections
Scabies
A condition due to the mite Sarcoptes scabiei seen in young adults and children
– The mite colonises the skin and lays eggs within the epidermis.
– This then leads to a type 4 hypersensitivity reaction to the eggs which can occur up to a month after initial exposure, usually by direct skin-skin contact
– This causes the release of inflammatory cytokines giving rise to a widespread itch.
Appearance
– Pruritus, which is particularly worse at night (12)
– Linear burrows (wavy, thread-like grey lines that can have a small vesicle with a
black do at the end). Seen on fingers, wrists and penis.
– Rash (erythematous papules) on side of fingers, web spaces and under the nails
Management
– Treat whole household contact even if asymptomatic
– If >2 months –> 1st line is permethrin cream 5%, then 2nd is malathion 0.5%
– Apply product to the whole body for 8-12 hours (permethrin) or 24 hours (malathion)
N.B. Crusted scabies is seen in immunosuppressed patients (e.g. HIV). This is a much more serious condition where the lack of immune system results in >100,000 mites in the skin making it crust significantly.
Management – Combination therapy with topical insecticide and oral ivermectin
Head lice (Pediculosis capitis)
This is a common condition caused by the parasite Pediculus capitis on human scalp – Spread by direct head-to-head contact so seen in children who play together
Symptoms
– Repeated itching and scratching of the scalp
Diagnosis
– Detection combing of wet or dry hair (wet hair more accurate)
– A live louse must be found to confirm infestation and treat
Management – Continue to send children to school + check whole household
– 1st line is Web combing -> if pregnant, breastfeeding, child <2 or asthma
– Chemical insecticide -> Malathion – Physical insecticides -> Dimeticone, isopropyl myristate or cyclomethicone
