Contributors: John M. Kissane and John D. Pfeifer
Staphylococcal blepharitis is a chronic inflammation of the eyelid margins caused by Staphylococcus. S. aureus is the usual pathogen; S. epidermidis and S. saprophyticus produce lesions in special circumstances. After birth, staphylococci . from the environment colonize the infant's umbilical stump, skin, perineum and sometimes the gastrointestinal tract. A carrier state, usually in the anterior nasopharynx is maintained throughout life in 20 to 40% of human beings. Staphylococci can gain access to tissues through an accidental or deliberate injury in the skin, or via the blood or lymphatic system. Physicians, nurses, and hospital attendants are more than normally susceptible to staphylococcal colonization as are diabetic patients receiving insulin, patients on hemodialysis, and intravenous drug abusers. Staphylococci resist drying and persist for months on contaminated surfaces. There is no significant non-human biologic resevoir.
S. aureus produces a variety of cutaneous and subcutaneous lesions, among which are the conveniently described pyodermas (or localized infections), and those with systemic manifestations such as skin rash. When staphylococci reach specific organ sites either by penetrating trauma, contiguity to a purulent focus or transmission by the blood or lymphatic streams, important organ infections result. When staphylococci gain access to tissues the organisms evoke a typical acute inflammatory reaction of which the principal constituent is the polymorphonuclear leukocyte. Soon central necrosis in such a focus of inflammation gives rise to pus, a mixture of fibrin, living and dead bacteria, leukocytes, and products of tissue breakdown. S. aureus secretes a large array of enzymes and toxins that contribute to its pathogenicity. S. aureus is a transient colonizer of the eyelids. Staphylococcus is a cause of chronic blepharitis and hordeolum. S. aureus and coagulase negative staphylococci cause blepharitis. Two types of blepharitis exist: (1) seborrheic blepharitis, characterized by hard fibrinous scales surrounding cilia, and (2) ulcerative blepharitis, which is less common, characterized by matted hard crusts encircling the cilia. Both types may have dilated blood vessels on the eyelid margins, poliosis, madarosis, and thin, broken eyelashes. Patients may also have recurrent chalazia and styes. Chronic papillary conjunctivitis usually accompanies the blepharitis. S. aureus is a less common cause of purulent conjunctivitis in neonates as well as adults. Keratitis and phylctenulosis may occur. Staphylococcal keratitis typically follows a corneal insult, such as an abrasion, surgical suture, exposure to contaminated contact lenses, or prolonged use of topical steroids. Development of corneal catarrhal marginal ulcers during S. aureus infection represents a hypersensitivity reaction that depends on the development of cell mediated immunity to staphylococcal antigens. S. aureus and coagulase negative staphylococci also cause blepharitis and phlyetenules. Staphylococcus is the most frequent cause of bacterial endophthalmitis and infectious dacryocystitis.
Implantation of S. aureus by penetrating trauma, or spread from cutaneous infections adjacent to the eye, may cause orbital cellulitis.