Sunday 5 February 2006
Whether the lesion is located in the skin, lungs, bones, or heart valves, S. aureus causes pyogenic inflammation that is distinctive for its local destructiveness.
Staphylococcal skin infections
Excluding impetigo, which is a staphylococcal or streptococcal infection restricted to the superficial epidermis, staphylococcal skin infections are centered around the hair follicles.
A furuncle, or boil, is a focal suppurative inflammation of the skin and subcutaneous tissue, either solitary or multiple or recurrent in successive crops. Furuncles are most frequent in moist, hairy areas, such as the face, axillae, groin, legs, and submammary folds.
Beginning in a single hair follicle, a boil develops into a growing and deepening abscess that eventually "comes to a head" by thinning and rupturing the overlying skin.
Carbuncles typically appear beneath the skin of the upper back and posterior neck, where fascial planes favor their spread. Chronic abscess formation of apocrine gland regions, most frequently of the axilla, is known as hidradenitis suppurativa.
Those of the nail bed (paronychia) or on the palmar side of the fingertips (felons) are exquisitely painful. They may follow trauma or embedded splinters and, if deep enough, destroy the bone of the terminal phalanx or detach the fingernail.
Staphylococcal lung infections
Staphylococcal lung infections have a polymorphonuclear infiltrate similar to that of pneumococcus but are much more destructive of lung tissues. S. aureus lung infections usually occur in patients with predisposing conditions such as influenza or hematogenous spread of infected thrombi.
Staphylococcal scalded skin syndrome (SSSS), also called Ritter disease, is caused by the exfoliative A and B toxins.
It is an exfoliative dermatitis that most frequently occurs in children with staphylococcal infections of the nasopharynx or skin. In staphylococcal scalded skin syndrome, there is a sunburnlike rash that spreads over the entire body and forms fragile bullae that lead to partial or total skin loss.
The intraepithelial split in staphylococcal scalded skin syndrome is in the granulosa layer, distinguishing it from toxic epidermal necrolysis, or Lyell’s disease, which is secondary to drug hypersensitivity and causes splitting at the epidermal-dermal junction.