Skin infection

Skin Infections

Omar Y. Abdullah

Bacterial skin infections

Why does skin get infected?
There are multiple types of bacteria which are normally present on the skin. For example: Staphylococcus epidermidis and yeasts The presence of bacteria does not automatically lead to a skin infection What is the difference between colonisation and infections???


Colonisation: Bacteria are present, but causing no harm Infection: Bacteria are present and causing harm. A break in the epidermal integrity can allow organisms to enter and become pathogenic. This can occur as a result of trauma, ulceration, fungal infection, skin disease such as eczema

Impetigo

A highly infectious skin disease, which commonly occurs in children.

The causative organism is usually Staphylococcus Aureus (>90% cases1), but less often can be strep pyogenes. Begins as a vesicle, which may enlarge into a bulla. Weeping, exudative area with characteristic honey coloured or golden, gummy crusts, which leave denuded red areas when removed. Usually on the face around the mouth, but any area could be affected.


Impetigo
Treatment:Mild localised cases - use topical antibiotic Polyfax Widespread or more severe infections – use systemic antibiotics, such as flucloxacillin (or erythromycin if penicillin allergic)

Folliculitis

Inflammation of the hair follicle. Presents as itchy or tender papules and pustules at the follicular openings. Complications include abscess formation and cavernous sinus thrombosis if upper lip, nose or eye affected.A

Most common cause is Staph Aureus.Other organisms to consider include:Gram negative bacteria – usually in patients with acne who are on broad spec antibioticsPseudomonas (“Hot tub folliculitis”)Yeasts (candida and pityrosporum)

Folliculitis treatment

Topical antiseptics such as ChlorhexidineTopical antibiotics, such as Fusidic acid or MupirocinMore resistant cases may need oral antibioics such as FlucloxacillinHot tub folliculitis – ciprofloxacinGram negative – trimethoprim

Cellulitis

Infection of the deep subcutaneous layer of the skin Presents as a hot, tender area of confluent erythema of the skin Can cause systemic infection with fever, headache and vomiting. Erysipelas is more superficial and has a more well demarcated border

Erysipelas

Cellulitis
Streptococcus – Group A Strep Pyogenes.Others include Group B, C, D strep, Staphylococcus Aureus, haemophilus influenzae (children) and anaerobic bacteria (e.g Pasteurella spp. After animal bites)

Treatment of cellulitis

Oral Flucloxacillin or erythromycin if allergicCo-amoxiclav in facial cellulitisIf severe systemic upset, may require admission for IV antibiotics. After the acute attack has settled, especially in recurrent episodes – consider the underlying cause


Orbital cellulitis – refer urgently

Staphylococcal Scalded Skin Syndrome

A superficial blistering condition caused by exfoliative toxins of certain strains of Staph Aureus Usually in children less than 5 yrs old Characterised by blistering and desquamation of the skin and Nikolsky's sign (shearing of the epidermis with gentle pressure), even in areas that are not obviously affected

begins with a prodrome of pyrexia and malaise, often with signs and symptoms of an upper respiratory tract infection discrete erythematous areas then develop and rapidly enlarge and coalesce, leading to generalised erythema - often worse in the flexures with sparing of the mucous membranes large, fragile bullae form in the erythematous areas and then rupture

Complications include hypothermia, dehydration and secondary infection. Treatment: ABC, refer urgently for IV antibiotics and fluids, may need referral to tertiary burns centre

What is the diagnosis?

Painful red nodule

Furunculosis (boils) and carbuncles

Deeper Staphylococcal abscess of the hair follicle Coalescence of boils leads to the formation of a carbuncle Treatment is with systemic antibiotics and may need incision and drainage. Consider looking for underlying causes, such as diabetes

Erythrasma

Colonisation of axillae or groin with Corynebacterium Minutissimum. Presents as a fine, reddish brown rash in the flexures, which is sharply marginated. Often misdiagnosed as a fungal infection Woods light illumination produces a characteristic coral-pink fluorescence. Treatment is with topical fusidin cream.


When you use the Wood’s light, the skin lesion shows a dramatic coral pink fluorescence.

Viral Skin Infections

Viral warts and verrucas
Caused by human papilloma virusMain types, common, plane and plantarVery commonDisappear spontaneously eventuallyIf treatment is needed, options include:Salicylic acid topically – needs daily treatment and can take monthsCryotherapyImiquimod cream

Molluscum contagiosum

Caused by DNA pox virusCommon in children, but can occur at any ageSpread by direct contactPresents as multiple small, pearly, dome-shaped papules with central umbilicationCan occur at any siteUsually resolve spontaneously in 6-18 monthsResolution is heralded by the development of erythema around the lesions. Treatment is not usually necessary – simple reassurance and advice about reducing transmission. If treatment is necessary, options include:Piercing the lesion with an orange stick tipped with iodineCurretageimiquimod cream

Herpes Zoster (Shingles )

Caused by reactivation of the chickenpox virus which has lain dormant in the dorsal root or cranial nerve ganglia Rash is preceded by a prodromal phase of up to 5 days of tingling or pain Then develop painful grouped vesicles/pustules on a red base in a dermatomal distribution. Most common in thoracic and trigeminal areas Lesions become purulent, then crusted Healing takes place in 3-4 weeks

Shingles treatment

Aciclovir 800mg 5 times daily, for 7 days Rest, analgesia Complications include: Post herpetic neuralgia Secondary infection Guillain Barre Syndrome Occular disease

Post-herpetic Neuralgia

Pain lasting longer than 3 months after the rash. The followings are risk factors for developing post-herpetic neuralgia? A: Older age B: More severe pain during the eruption C: Severely inflamed rash D: Prodromal pain in dermatome


Herpes Simplex Virus
A highly contagious infection spread by direct contactHSV 1 : also commonly called “coldsore”HSV 2 usually presents on the genitaliaPrimary infection is usually asymptomatic.Recuurent infection presents as acute, painful gingivo-stomatitis with multiple small intra/peri-oral ulcers (but any site could be affected). Associated with fever, malaise and lymphadenopathy.

Genital herpes

Herpetic Whitlow
Herpes Simplex Keratitis


Clinically: Grouped umbilicated vesicles/pustules on erythematous base. Treatment: Topical aciclovir can be used: 5 times daily for 5 days. Reduces duration of attack and duration of viral shedding. The correct dose of aciclovir for HSV is 200mg 5 times daily for 5 days

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