skin infection pdf - د.هيثم بدر

Fifth stage

Dermatology

Lec-3

.هيثم

29/12/2016

Bacterial skin infections

Viral skin infections

Fungal skin infections

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.



May present as macules, vesicles, bullae or pustules



Bullae are more prominent in staphylococcal infection and in infants
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.



Most common cause is Staph Aureus.



Other organisms to consider include:



Gram negative bacteria – usually in patients with acne who are on broad spec
antibiotics



Pseudomonas (“Hot tub folliculitis”)



Yeasts (candida and pityrosporum)

Folliculitis treatment
 Topical antiseptics such as Chlorhexidine
 Topical antibiotics, such as Fusidic acid or Mupirocin
 More resistant cases may need oral antibioics such as Flucloxacillin
 Hot tub folliculitis – ciprofloxacin2
 Gram 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 allergic



Co-amoxiclav in facial cellulitis



If severe systemic upset, may require admission for IV antibiotics.



After the acute attack has settled, especially in recurrent episodes – consider the
underlying cause

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
generalized 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

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 virus



Main types, common, plane and plantar



Very common



Disappear spontaneously eventually



If treatment is needed, options include:



Salicylic acid topically – needs daily treatment and can take months



Cryotherapy



Imiquimod cream

Molluscum contagiosum



Caused by MC virus



Common in children, but can occur at any age



Spread by direct contact



Presents as multiple small, pearly, dome-shaped papules with central umbilication



Can occur at any site



Usually resolve spontaneously in 6-18 months



Resolution 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 iodine



Curretage



imiquimod 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 usually gabapentine.

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 contact



HSV 1 : also commonly called “coldsore”



HSV 2 usually presents on the genitalia



Primary infection is usually asymptomatic.



Recuurent infection presents as acute, painful gingivo-stomatitis with multiple small
intra/perioral ulcers (but any site could be affected).
Associated with fever, malaise and lymphadenopathy.



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