Updates on the Management of Bacterial Keratitis

Posted by e-Medical PPT Saturday, February 18, 2012
Infective Keratitis:
30,000 cases annually in the US (Bacterial, Fungal and Acanthanoeba)Bacterial Keratitis rarely occurs in normal eyes because of human cornea’s natural resistance to infection

Risk Factors-Exogenous factors :
Contact lens use Trauma Previous ocular/eyelid surgery Loose sutures Previous Corneal Surgery (incl. Lasik & PRK) Medication related and medicamentosa (contaminated ocular medications, topical NSAIDS, anesthetics, antimicrobials, preservatives, glaucoma medications) Immunosuppresion Factitious disease (incl. anesthetic abuse)

Risk Factors-Ocular Surface Disease:
Misdirection of eyelashes Abnormalities of eyelid anatomy and function (incl. exposure) Tear film deficiencies Adjacent infections: conjunctivitis incl gonococcal, blepheritis, canaliculitis, dacrocysytitis

Risk factors-Corneal Epithelial Abnormalities :
Neurotrophic Keratopathy Disorders predisposing to recurrent corneal erosion Viral Keratitis Corneal epithelial oedema, especially bullous keratopathy

Risk factors-Systemic conditions:
Diabetes mellitus Debilitating illness ( malnourishment and respirator dependence) Collagen vascular disease Substance abuse Deramtological/ mucous membrane disorders (e.g. Stevens-Johnson syndrome, ocular cicatricial pemphigoid) Immunosuppressed status Atopic dermatitis/ Gonococcal infection and conjunctivitis Vitamin A deficiency

Common etiological agents of bacterial keratitis in the U.S. (AAO Preferred Practice Pattern Aug 2005-Bacterial Keratitis) :
Class/Organism Common Isolates* Cases (%) Gram-Positive Isolates 44–90 Gram-positive Cocci Staphylococcus aureus 4–30 Coagulase negative Staphylococci 5–40 Streptococcus pneumoniae 1–25 Streptococcus viridans group 1–15 Gram-positive Bacilli Corynebacterium species 1-5 Propionibacterium species 1-12 Mycobacterium species 1-2 Gram-Negative Isolates 10–50 Gram-negative Bacilli Pseudomonas aeruginosa 5-45 Serratia marcescens 1-12 Proteus mirabilis 1-5 Enteric gram-negative bacilli, other 1-10 Gram-negative Coccobacillary organisms Haemophilus influenzae, other 1-6 Haemophilus species 1-5 Moraxella species and related species Gram-negative Cocci Neisseria species 1 Common etiological agents of bacterial keratitis in the U.S. (AAO Preferred Practice Pattern Aug 2005-Bacterial Keratitis)

Natural History of Bacterial Keratitis:
Corneal scarring (significant visual loss if invl. central visual axis) Corneal perforation Endophthalmitis Rapid progression(24 hrs)-pseudomonas, gonococcal Indolent course atypical mycobacteria, viridans type streptococcus

Prevention and Early Detection:
Screening of patient with high risk factors Education on use of extended wear contact lens Protective eye wear for work and sports Treatment of ocular surface disease Use of prophylactic antibiotics is controversial both in its effectiveness and risk of promoting bacterial resistance (except in the following -removal of loose suture & corneal FB)

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