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Skin infections

Bacterial case challenge 2

The skin problems have developed over the last two weeks in siblings.

Which terms best describe the morphology of the lesions? # Abscess #! Crusting || Hard surface deposit. Occurs when plasma exudes through an eroded epidermis. It is rough on the surface and is yellow or brown in colour. Bloody or haemorrhagic crust appears red, purple or black. # Nodule #! Plaque || A palpable flat lesion greater than 0.5 cm diameter. Most plaques are elevated, but a plaque can also be a thickened area without being visibly raised above the skin surface. They may have well-defined or ill-defined borders. What is the most appropriate diagnosis: * Ecthyma * Furunculosis *! Impetigo * Abscess Explanation: The images show inflammatory crusted plaques, characteristic of impetigo. The younger child has very extensive areas of erythema with peripheral crusting (dried-up bullae). Explanation: Ecthyma is non-follicular ulcerated impetigo. Furunculosis results in pustules and crusted nodules. Abscesses are nodules greater than 1cm in diameter full of pus.

Which are the likely organisms?

#! _Staphylococcus aureus_ #! _Streptococcus pyogenes_ # Diphtheroids # _Proprionibacterium acnes_ Explanation: Impetigo is caused by Staphylococcus aureus and/or Streptococcus pyogenes. In these children, both organisms were present on culture.

Prior to developing impetigo, both children had an itchy rash affecting the trunk and limbs.

What underlying skin conditions should be considered: #! Varicella #! Scabies # Headlice #! Atopic dermatitis Explanation: Secondary infection is very common in atopic dermatitis and scabies. Although less common after varicella infection, secondary streptococcal infection can be very serious. Head lice may also cause secondary infection of the scalp and neck but do not result in an itchy rash on trunk and limbs.

The children are treated with oral antibiotics. Which of the following are suitable?

#! Erythromycin # Amoxicillin #! Flucloxacillin #! Amoxicillin/clavulanic acid Explanation: In New Zealand, 80-90% Staphylococcus aureus is currently (2003) resistant to penicillin and amoxicillin. Penicillinase-resistant penicillins, such as flucloxacillin or dicloxacillin, or the broad-spectrum beta-lactamase inhibitor amoxicillin/clavulanic acid, should be used. Erythromycin is suitable for penicillin-allergic subjects (5-10% resistance rates).