Impetigo

Dermatology

Clinicals - History

Fact Explanation
Pruritic skin lesions Due to infection by staphylococcus aureus and group A streptococcus. Pruritus is seen especially if associated with atopic dermatitis, ie. owing to the inflammation . Pruritic skin lesions
Due to infection by staphylococcus aureus and group A streptococcus. Pruritus is seen especially if associated with atopic dermatitis, ie. owing to the inflammation .
History of predisposing factors: injury to skin, genetic & inflammatory conditions and cutaneous infections These predisposing factors act as portals of entry for pathogenic organisms. Minor cuts / ulcers cause primary impetigo while atopic dermatitis / insect bites / porphyria cutania tarda / sunburn / bullous pemphigoid /
chronic lymphedema / cutaneous infections with herpes simplex, varicella zoster, herpes zoster and dermatophytes cause secondary impetigo .
History of predisposing factors: injury to skin, genetic & inflammatory conditions and cutaneous infections
These predisposing factors act as portals of entry for pathogenic organisms. Minor cuts / ulcers cause primary impetigo while atopic dermatitis / insect bites / porphyria cutania tarda / sunburn / bullous pemphigoid /
chronic lymphedema / cutaneous infections with herpes simplex, varicella zoster, herpes zoster and dermatophytes cause secondary impetigo .

Clinicals - Examination

Fact Explanation
Non-bullous impetigo: Skin lesions are 1-3 cm size erosions with golden crusting. Central healing and satellite lesions may be present. Satellite lesions occur by autoinoculation . Usually there are multiple lesions in a single patient, mostly involving the face .
Note: The golden/honey color of the lesions is not a distinguishing feature of impetigo, as there are other causes for this presentation as well .
Non-bullous impetigo: Skin lesions are 1-3 cm size erosions with golden crusting. Central healing and satellite lesions may be present.
Satellite lesions occur by autoinoculation . Usually there are multiple lesions in a single patient, mostly involving the face .
Note: The golden/honey color of the lesions is not a distinguishing feature of impetigo, as there are other causes for this presentation as well .
Bullous impetigo: skin lesions are bullae and vesicles containing fluid/pus, with surrounding erythema. Exfoliative toxins of staphylococcus aureus produce blistering by cleaving cell adhesion molecules. When the bullae are ruptured yellowish exudate is released, followed by crust formation .
This is considered the localized form of staphylococcal scalded skin syndrome .
Bullous impetigo: skin lesions are bullae and vesicles containing fluid/pus, with surrounding erythema.
Exfoliative toxins of staphylococcus aureus produce blistering by cleaving cell adhesion molecules. When the bullae are ruptured yellowish exudate is released, followed by crust formation .
This is considered the localized form of staphylococcal scalded skin syndrome .
Underlying skin conditions predisposing to impetigo may be observed. Patients with atopic dermatitis / sunburns / abrasions / lymphedema / ulcers are more prone to develop impetigo, as a breach in the skin is essential for staphylococcal infection . Underlying skin conditions predisposing to impetigo may be observed.
Patients with atopic dermatitis / sunburns / abrasions / lymphedema / ulcers are more prone to develop impetigo, as a breach in the skin is essential for staphylococcal infection .

Investigations - Diagnosis

Fact Explanation
Gram stain of the skin lesions Will show gram positive cocci in clusters in staphylococcal infection, and gram positive cocci in chains in streptococcal infection .
Note: the diagnosis is made clinically and can be confirmed by the investigations if required only .
Gram stain of the skin lesions
Will show gram positive cocci in clusters in staphylococcal infection, and gram positive cocci in chains in streptococcal infection .
Note: the diagnosis is made clinically and can be confirmed by the investigations if required only .
Bacterial culture of the skin lesions Will show the growth of causative organisms . Bacterial culture of the skin lesions
Will show the growth of causative organisms .

Management - Supportive

Fact Explanation
Preventive measures Daily bath with benzyl peroxide wash helps to eliminate methicillin resistant staphylococcus aureus (MRSA) . Intranasal mupirocin ointment, chlorhexidine gluconate washes, oral doxycycline & rifampicin are also effective in eradicating MRSA. However, susceptibility testing should be done before starting treatment with mupirocin, due to the developing resistance . Preventive measures
Daily bath with benzyl peroxide wash helps to eliminate methicillin resistant staphylococcus aureus (MRSA) . Intranasal mupirocin ointment, chlorhexidine gluconate washes, oral doxycycline & rifampicin are also effective in eradicating MRSA. However, susceptibility testing should be done before starting treatment with mupirocin, due to the developing resistance .

Management - Specific

Fact Explanation
Topical antibiotics Application of neomycin, fusidic acid, mupirocin or bacitracin after removal of the crust is sufficient for minor lesions . Topical mupirocin is superior to oral erythromycin in eradicating MRSA . Note: sometimes the lesions heal even without treatment . Topical antibiotics
Application of neomycin, fusidic acid, mupirocin or bacitracin after removal of the crust is sufficient for minor lesions . Topical mupirocin is superior to oral erythromycin in eradicating MRSA . Note: sometimes the lesions heal even without treatment .
Systemic antibiotics Flucloxacillin, erythromycin or cephalexin is needed for severe lesions. Penicillin V is used for streptococcal strains that are at risk of causing glomerulonephritis .
Note: resistance rates to erythromycin are rising and is considered to be less effective .
Oral cephalexin is considered the drug of choice for systemic treatment in children .
Systemic antibiotics
Flucloxacillin, erythromycin or cephalexin is needed for severe lesions. Penicillin V is used for streptococcal strains that are at risk of causing glomerulonephritis .
Note: resistance rates to erythromycin are rising and is considered to be less effective .
Oral cephalexin is considered the drug of choice for systemic treatment in children .

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