Bacterial keratitis: Description, Causes and Risk Factors:The human eye is composed of mucosal surfaces, such as the mucosal epithelium of the cornea, as well as interior chambers, such as the vitreous humor, that are potential targets of bacterial infection. Bacterial infections of the eye can range from mild, self-limiting conjunctivitis to devastating panophthalmitis involving the entire orbit.Bacterial keratitis is a potentially sight-threatening disorder and the leading cause of monocular blindness worldwide. Ocular trauma is the leading cause of bacterial keratitis. Pseudomonas is the most common organism causing bacterial keratitis.Common causative organisms associated with bacterial keratitis are Pseudomonas aeruginosa, Staphylococcus aureus, coagulase-negative staphylococci, Streptococcus pneumoniae, Enterobacteriaceae (including Klebsiella, Enterobacter, Serratia, and Proteus). Less common gram-positive organisms include aerobic, spore forming bacilli Bacillus coagulans and B. brevis, as well as Corynebacterium diphtheriae.Different bacterial toxins and enzymes (including elastase and alkaline protease) may be produced during corneal infection, contributing to the destruction of corneal substance.Incidence of bacterial keratitis varies considerably, with less industrialized countries having a significantly lower number of contact lens users and, therefore, significantly fewer contact lens-related infections.Risk Factors:Contact lens wear.
Ocular surface disease.
Decreased immunologic defenses secondary to malnutrition, alcoholism, and diabetes (Moraxella).
The clinical criteria for presumed bacterial keratitis may include:Diffuse and/or severe progressive corneal suppuration.
Lesions often central but can be in any location.
Lesions >1mm in diameter.
Progressively deteriorating pain, sometimes severe
Symptoms:Symptoms of bacterial keratitis may include:Reduced vision.
Diagnosis:A meticulous history, thorough clinical examination, anddetailed microbiologic technique are vital steps insuccessful management.To accurately diagnose bacterial keratitis eye infection, your ophthalmologist may gently scrape the eye to take a small sample of material and test it for infection. He or she will also discuss your bacterial keratitis symptoms with you.Imaging:Slit lamp photography can be useful to document the progression of the keratitis, and, in cases where the specific etiology is in doubt, it is used to obtain additional opinions, particularly in indolent and chronic cases not responding to antimicrobial therapy.
A B-scan ultrasound can be obtained in eyes with severe corneal ulcers with no view of the posterior segment where endophthalmitis is being considered.
Corneal biopsy using a small trephine or a corneal blade should be considered in cases of deep stromal infiltrates, particularly if cultures are negative and the eye is not improving clinically.Treatment:The goals of therapy in a case of bacterial keratitis are eradication of viable bacteria from the cornea and rapid suppression of the inflammatory response elicited by the causative microorganisms.Bacterial keratitis is usually treated with antibiotic drops and may require multiple return visits to your ophthalmologist. Drops are usually put in frequently. Treatment may also involve a topical steroid applied to the eye.Topical antibiotics constitute the mainstay of treatment in cases of bacterial keratitis, with subconjunctival antibiotics used only under unusual circumstances, and systemic antibiotics used only in cases of perforation or specific organisms (eg, N gonorrhoeae). The use of topical corticosteroids remains controversial; however, when they are used, strict guidelines and close follow-up care are mandatory to ensure the best ultimate outcome of these patients.Antibiotics may include: Fortified tobramycin 14 mg/mL (AKTob, Tobrex), Amikacin 20 mg/mL (Amikin), Fortified cefazolin 50 mg/mL (Ancef, Kefzol, Zolicef), Ceftazidime 50 mg/mL (Fortaz, Ceptaz), Chloramphenicol ophthalmic (Chloromycetin), Erythromycin ophthalmic (E-Mycin), Vancomycin 50 mg/mL (Vancocin), Sulfacetamide ophthalmic, Ciprofloxacin 0.3% (Ciloxan), Ofloxacin ophthalmic (Floxin), Gatifloxacin ophthalmicTopical corticosteroids may include Prednisolone acetate 1% (AK-Pred, Pred Forte).NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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