THE TREATMENT AND MANAGEMENT OF MICROBIAL KERATITIS Joseph P. Shovlin, O.D., F.A.A.O. This presentation begins with a review of the epidemiology and pathogenesis of ulcerative keratitis in contact lens wear. Several recent landmark studies will be analyzed in order to cite the risk factors associated with the increased incidence of infection. Preventive measures in minimizing these occurrences will be stressed. The organisms most likely to be encountered will be reviewed along with the key measures used to make the important differential diagnosis between a sterile versus an infectious keratitis. As a primary care provider, the optometrist must be familiar with the appropriate treatment protocols in suspected and confirmed cases of ulcerative keratitis and what to do when these accepted standards of initial therapy fail. Finally, a few rare corneal pathogens will be reviewed as a cause of microbial keratitis. TOPICS: I. RISK FACTORS AND THE PATHOGENESIS OF ULCERATIVE KERATITIS II. THE DIFFERENTIAL DIAGNOSIS OF INFILTRATIVE KERATITIS III. TREATMENT PROTOCOLS FOR BACTERIAL ULCERATIVE KERATITIS IV. FUNGAL AND PROTOZOAN INFECTIONS OF THE EYE I. RISK FACTORS AND THE PATHOGENESIS OF ULCERATIVE KERATITIS IN CONTACT LENS WEARERS RISK FACTORS FOR BACTERIAL CORNEAL ULCERS EXOGENOUS: contact lenses, especially extended wear, contaminated cases and solutions, patching a contact lens abrasion; trauma including foreign body, chemical and thermal injury; previous ocular surgery including loose sutures; medicamentosa, contaminated medications and make-up. OCULAR ADNEXAL DYSFUNCTION: misdirection of lashes; abnormal lid anatomy & function; tear deficiencies, conjunctivitis; neuropathy involving cranial nerve(s) III, V and VII; blepharitis, canaliculitis/dacryocystitis. CORNEAL ABNORMALITIES: hypesthesia, bullous keratopathy, erosive disorders, viral keratitis. SYSTEMIC DISEASE: diabetes mellitus; debilitating illness, especially malnutrition or respirator dependence; collagen vascular disorders, substance abuse, mental illness; exfoliative skin disease; immunocompromised patient; atopic dermatitis, vitamin A or B deficiency. IMMUNOSUPPRESSIVE THERAPY: systemic corticosteroids; topical immunosuppressive agents; systemic chemotherapy for malignancy, organ transplant or collagen vascular disease. PATHOGENESIS Epithelial Compromise- hypoxic, mechanical, osmotic Contact Lens Contamination- lens care products, case,cosmetics, skin flora, adherence to lens Cascade of Events- adherence of microorganism to surface of cornea, invasion of the cornea, spread and multiplication, induction of the host inflammatory response, encounter of microorganisms with host immune factors, tissue damage, tissue repair and recovery EPIDEMIOLOGY [Adapted from O.D. Schein] RELATIVE RISK Population at risk- approximately 24 million lens wearers Overnight wear the overwhelming risk Relative risk of extended wear vs daily wear: 10-15:1 Overnight wear of disposable lenses equal risk Additional risk factors- aphakia, smoking, lens case cleaning, minimal protective effect of hygiene INCIDENCE Daily Wear: approximately 1/2,500/year Overnight wear of extended wear lenses: estimates range from one case among 150-300 wearers/year Population at risk- probably 12,000-15,000 cases /year in U.S. PREVENTION Minimizing overnight wear with careful patient selection Host Factors- diabetes, age, personal hygiene, unknown role of conjunctival flora Contact Lens Induced Changes- compromised/injured epithelium, tear film stagnation and reduced oxygen tension, elevated surface temperature Minimizing lens care contamination- wash hands, remove lenses at pre-determined intervals, clean and disinfect using FDA approved regimens, small bottles of solution to avoid contamination, lens case replacement and care, prophylactic antibiotics not recommended Warning signs: vision, comfort, appearance (observe < 2 hrs.) II. THE DIFFERENTIAL DIAGNOSIS OF INFILTRATIVE KERATITIS BACTERIAL FLORA OF THE NORMAL EYE Staphylococcus epidermidis Diphteroids (C. xerosis) Staphylococcus aureus Streptococcus (S. viridans) Hemophilus influenza Streptococcus pneumoniae Gram negative rods Pseudomonas aeruginosa 75-90%* 20-33% 20-25%* 2-6% 3% or more 1-3%* 1% or more* 0-5%* *Dominant organisms for microbial keratitis CLINICAL FEATURES Symptomotology- pain, photophobia, decreased acuity, foreign body Signs-significant lid edema and reactive ptosis, conjunctival and ciliary injection, discharge, papillary response, stromal infiltration, surrounding edema, epithelial defect, anterior chamber reaction, cellular debris of the tear meniscus, and hypopyon DISTINCTIVE SIGNS Epithelium Stromal inflammation Site of inflammation Typical Atypical ulcerated suppurative focal*, diffuse intact non-suppurative multifocal *multifocal, suppurative keratitis suggestive of mixed infection INDICATIONS FOR CULTURES Mandatory Recommended Rarely Helpful corneal ulcers neonatal conjunctivitis hyperacute conjunctivitis dacryocystitis chronic conjunctivitis chronic blepharitis hospital acquired infections ulcerative conjunctivitis epidemic conjunctivitis atypical external disease follicular conjunctivitis dendritic ulcer acute blepharitis papillary conjunctivitis hordeolum/chalazian corneal abrasion allergic conjunctivitis LABORATORY CONFIRMATION/SCRAPINGS Smears- Gram, Giemsa, acridine orange, acid fast, methenamine silver, calcofluor white Cultures- blood agar, chocolate agar (heated blood), thioglycolate broth, Sabouraud’s, Lowenstein-Jensen, non-nutrient agar, and others like Thayer-Martin medium for suspected Neisseria infections Methods of obtaining material-corneal swabing & scraping, superficial keratectomy, biopsy, lamellar keratoplasty Equipment-Bunsen burner, magnification, anesthetic, swabs, spatula, glass slides, culture media, fixative, stains, lab form Suggestions for increasing value of lab tests- follow the same technique regardless of the clinical impression, use fresh media removed from refrigeration several minutes prior to plating, do not use transport media, use unpreserved anesthetic (lidocaine),work with magnification, multiple samples on multiple media, fix slides promptly, culture each site as indicated by location of disease, recognize any growth as potentially important, when relevant culture contact lens paraphernalia, in-use medications (micro-antibiotic removal devices may be helpful in patients who have received therapy prior to culturing) Reasons to culture before treatment- reveal sensitivities of organisms to eliminate ineffective drugs to reduce toxicity, discriminate between static and cidal properties of antibiotics and guide modification in therapy, ineffectively treated organisms are often difficult to isolate, medico-legal component of the patient’s record. CORNEAL BIOPSY Corneal biopsy is indicated if there has been a poor response to treatment or if cultures have been negative on more than one occasion, and the clinical picture continues to suggest infection. Also, used where a deep suppurration is not accessible by scraping. The specimen should be sufficiently large to allow bisection; one section for culture and the other for histopathology. Specimen should be delivered to the technician without delay. DOCUMENTATION DESCRIPTION OF THE ULCER: Document- size and shape of the epithelial defect, depth and location of the infiltrate and surrounding stromal inflammation, presence or absence of anterior chamber and cellular debris of the tear meniscus, and scleral involvement GRADING OF THE ULCER: Mild Moderate Severe Size of the defect (mm.) Depth of ulcer (%) Infiltrate <2 < 20 superficial Sclera not involved 2-5 20-50 dense, midstromal not involved >5 > 50 dense, past mid-stroma may be involved III. TREATMENT PROTOCOLS FOR MICROBIAL KERATITIS ASSESSMENT OF SEVERITY/ INITIAL PLAN OBJECTIVES To distinguish severe suppurative keratitis from non-severe Implications of virulent versus lesser virulent organisms Definition of latitudes of initial therapy GUIDELINES [Adapted from J. McCulley] Feature Suppurative/Severe Non-suppurative/Mild-Mod. Onset/progression acute/ rapid Virulence Laboratory Studies Laboratory Materials Initial Antibiotics highly likely immediate, urgent standard based on smears/broad antimicrobial agents sub-acute, chronic/slowly progressive uncertain, doubtful may delay special based on smears + biopsy/ latitude for deferral PRINCIPLES Broad spectrum of initial coverage: single agent (fluoroquinolones) vs. multiple agents Rapid, intensive topical therapy Daily evaluation Tailor antibiotic choice by culture results and clinical response DESIGN FOR DRUG PENETRATION Topical- every 15 min.- 1 hr. for initial 24-48 hrs. or altered loading dose Collagen shield- 12 hr. shield reconstituted in water soluble fortified antibiotic Subconjunctival injections- once or twice daily for 1-2 days Intravenous antibiotics- only for impending perforation or scleral suppuration MECHANISMS OF ACTION OF ANTIBIOTICS 1. Inhibition of bacterial cell wall synthesis (Penicillins, Cephalosporins, Bacitracin and Vancomycin) 2. Increasing the permeability of the bacterial cell wall (Polymixin B, Colistin, Gramicidin) 3. Inhibition of bacterial protein synthesis (Aminoglycosides, Tetracycline, Erythromycin, Chloramphenicol and Clindamycin) 4. Inhibition of bacterial intermediary metabolism (folic acid synthesis)(Sulfonamides, Pyrimethamine and Trimethoprim) 5. Interference with bacterial DNA synthesis (Quinolones and Nalidixic acid) INITIAL THERAPY OF INFECTIOUS KERATITIS [Adapted from A. Matoba]* *depends on severity, individual risk factors, initial gram stain results and clinical impression Organism Antimicrobial Topical Dose Subconj. Dose Gram + cocci Cefazolin 50 mg/ml, every 15-30 minutes 100 mg in 1/3 ml Gram - rods Tobramycin or gentamicin 13.6 mg/ml, every 15-30 minutes 20 mg in 1/2 ml No organism or multiple organisms Cefazolin and tobramycin see above dosages for each agent Gram + rods Penicillin and gentamycin 100,000 units/ml, every 15-30 minutes, see above for gentamycin Gram - cocci Ceftriaxone or ceftazidime 50 mg/ml, every 1530 minutes Acid-fast bacilli Amikacin 20 mg/ml, every 1530 minutes 20 mg in 1/2 ml MODIFICATION OF THERAPY Objectives- eliminate replicating bacteria, avoid adverse reaction to the medication, control the destructive components of the inflammatory process Guidelines- avoid abrupt changes in therapy until the response can adequately be assessed and until the sensitivity tests are completed at the lab Expected response despite proper/ effective therapy: Organism Response S. aureus, S. pneumoniae may be relatively unchanged, then improve rapidly after 24-48 hrs.; organisms generally eliminated in 7-10 days Pseudomonas aeruginosa generally appears worse at 24 hrs.; organism may persist for 14 days or longer Bacteria of low virulence (ie. S. epidermidis) generally improve rapidly in 24-48 hrs.; organisms eliminated in 5-7 days Mycobacterium, Filamentous fungi slow response; may persist for weeks RESISTANT BACTERIA* Methicillin resistant Staphylococcus aureus Enterococcus fecalis (group D Streptococcus) Aminoglycoside resistant Pseudomonas aeruginosa Beta lactamase producing Neisseria Atypical Mycobacteria Current antibiotic recommendation for suspected resistance: Vancomycin 20-30 mg/ml (Vancocin) and Ceftazidine 50 mg/ml (Fortaz/Pentacef) Gram positive organisms: Vancomycin 20-30 mg/ml (Vancocin) or Cefazolin 50 mg/ml (Ancef), .28% Lysostaphin Gram negative organisms: Amikacin 10-20 mg/ml (Amikin) FLUOROQUINOLONE RESISTANCE* Some concern for streptococcus species, enterococci, non-aeruginosa pseudomonas, and some MRSA UCSF Study (1996) Hwuang et al.: topical ciprofloxacin qid. staph. aureus resistance rose from 12%-50% with in-vitro testing Wills Eye Hospital Study (1996) Rodman et al.: Staphylococcus aureus resistance1992: 4% 1996:13% Streptococcus resistance1992:20% 1996:26% LV Prasad Eye Institute Study (1999) Kunimoto et al.: 30.7% of isolates from corneal infections were not sensitive to ciprofloxacin in India; Garg et al.: true pseudomonas resistance to ciprofloxacin is emerging *significant increase in in-vitro resistance with ciprofloxacin; clinical significance is uncertain/fewer pseudomonas infections in CL wearers. (geographical differences remain) ADJUVANT THERAPY Cycloplegia- for comfort and to prevent synechiae Collagenase inhibitors (ie. EDTA, TCN, Galardin)- to minimize stromal destruction Heat (40 degrees C) Steroids- hazardous early in treatment, safety and efficacy not well established in most forms of microbial keratitis; helpful in reducing harmful destruction due to host response NSAIDs/ Analgesics- reduces inflammation and pain, may enhance antimicrobial(s) efficacy (NSAIDs) *anecdotal reports suggest very effective for pain in mycobacteria infections Tissue adhesives- for impending and actual perforations if small/ bacteriostatic Glaucoma medication- if needed, beta-blockers is drug of choice Debridement/ Biopsy- may improve antibiotic penetration Cryotherapy- possible role in sclerokeratitis Bandage lens/ Collagen shield- may promote re-epithelialization and allow for slow concentrated release of antibiotic Continuous antibiotic infusion devices- possible benefit in extensive sclerokeratitis Therapeutic keratoplasty- for large perforations, central/deep medically recalcitrant keratitis INDICATIONS FOR HOSPITALIZATION Inability of patient/ family to deliver high frequency, 24 hr. treatment Inability to return initially for daily follow-up Threatening perforation or scleral involvement TERMINATION OF THERAPY Elimination or substitute antibiotics only if directed by lab results Elimination of the less effective agent if combined microbial therapy initiated for monobacterial keratitis after lab results Measures of improvement: Blunting of the perimeter of stromal suppuration Reduction in the density of suppuration Reduction in cellular infiltrate and edema in surrounding stroma Reduction in the anterior chamber reaction Progressive re-epithelialization Reducing antimicrobials and adjuvants: Avoid abrupt cessation; prolonged therapy needed for Pseudomonas, Mycobacterium, Nocardia, anaerobes Reduce by “halving method”, substitute regular/commercial strength for fortified antibiotics when possible Penetrating Keratoplasty Progressive suppuration despite appropriate therapy Persistent infection Corneal perforation not managed by other methods IV. FUNGAL AND PROTOZOAN INFECTIONS IN CONTACT LENS WEAR FUNGAL KERATITIS Fungi are primitive non-motile plant-like organisms. Yeast are uni-cellular and molds are multi-cellular filamentous structures. In the past 10 years there has been a definite increase in the prevalence of fungal keratitis in certain geographic areas, although nationwide there are probably only 300 cases per year. There are 40 different genera that cause keratomycoses; most are saprophytic. CLASSIFICATION/MOST COMMON ORGANISMS (Adapted from J. McCulley) Filamentous fungi; Molds Septate- most common cause of fungal keratitis, variable geographic distribution, mostly in the southern and southwestern United States,- Nonpigmented: Fusarium (most virulent due to complex enzymes + toxins), Aspergillus, Pigmented:Curvularia, Paecilomyces, Phialophora Non-septate- Mucoraceae (rare corneal pathogen) Risk Factors: corneal injury (frequently a tree branch or vegetative matter in an agricultural setting), soft contact lens wear (extended wear/therapeutic), chronic topical medication, systemic steroids, diabetes mellitus, radial keratotomy. CLINICAL FEATURES Epithelium Type of stromal inflammation Site of inflammation* Typical Atypical, severe intact or ulcerated non-suppurative, feathery infiltrate(s) focal or multi-focal, satellite infiltrates ulcerated suppurative diffuse *typically accompanied by a mild iritis, endothelial plaque and hypopyon in severe infections; hypopyon is of no diagnostic value Yeasts- worldwide distribution: Candida- C. albicans, C. parapsilosis, C. tropicalis Risk Factors- protracted ulceration of the epithelium, topical steroid therapy, penetrating keratoplasty, bandage soft lenses Epithelium Type of stromal inflammation Site of inflammation Typical, common Atypical, rare ulcerated suppurative intact non-suppurative focal or diffuse multifocal Note: ring infiltrates or abscess is possible with an intact epithelium KERATOMYCOSES DIAGNOSIS- clinical suspicion, corneal scraping, superficial keratectomy (paracentesis) Diagnostic stains- Gram, Giemsa, GMS, PAS, KOH, acridine orange, Schwartzman’s, calcofluor white Culture media- Sabouraud dextrose agar (with gentamicin, without Confocal cyclohexamide), blood agar, brain-heart infusion agar with gentamicin @ 25 + 37 C microscopy- identifies hyphae, poor for Candida, a guide to therapeutic response ANTIFUNGAL DRUG MECHANISMS OF ACTION1. Sterol Binding- Polyene drugs like Amphotericin B, Nystatin and Natamycin 2. Inhibition of Sterol Synthesis- the Imidazoles including Miconazole, Ketoconazole, Clotrimazole, Fluconazole 3. Interference with RNA Synthesis- Flucytosine (fluorinated pyrimidine) and Itraconazole (antimetabolites) 4. Inhibition of Mitosis- Griseofulvin INITIAL THERAPY- drugs are generally not introduced until definitive diagnosis is made. Topical*-HYPHAE-Natamycin 5% (Natacyn) suspension (every hr. for 2448 hrs.) YEAST OR PSEUDOHYPHAE- Amphotericin B .1-.5% (Fungizone) (every 15-20 minutes for 24-48 hrs.), Miconazole 1% (Micatin, Monistat) (every hr., but very toxic) as an alternate therapy. Clotrimazole (cream or powder) and Flucytosine (Ancobon tablets) converted to a 1% solution have been effective against Candida infection. Oral- Ketoconazole (Nizoral) (200-400 mg/day) or Fluconazole (Diflucan) (100-200 mg/day) [generally used for hyphae and endophthalmitis; Candida generally responds to topicals alone]; Itraconazole (Sporanox) is more effective against filamentous fungi especially Aspergilli .Reserve systemic treatment for deep keratitis, impending perforation, scleritis, endophthalmitis and post penetrating keratoplasty. Sub-conjunctival injection-Fluconazole (Diflucan) .5ml = 1mg daily pending initial response and identification of the organism. Other agents- atropine 1% or hyoscine .25% 4x/day; glaucoma medication as needed; role of collagen shield as a delivery device not well defined. Avoid steroids in fungal keratitis since mold/yeast replicate more freely and microbial agents are generally only fungistatic. *topicals are often continued for 6 wks. or longer; watch for toxicity Note: excimer ablation may be of some value unless there is deep penetration. PREVENTION-minimize extended wear, therapeutic lens application whenever possible, avoid indiscriminate use of topical steroids. ACANTHAMOEBA KERATITIS Acanthamoeba keratitis remained a curiosity in the past; however recently this pathogen affecting primarily the cornea and sclera is recognized with increased frequency. Early detection will alter the course of therapy and ultimately affect outcome, therefore early diagnosis is critical. The risks factors that have been identified by epidemiologic studies, specifically as they relate to contact lens wear will be examined. THE ORGANISM- "a free living" protozoan (motile) with worldwide distribution; isolated from fresh water, well water, sea and brackish water, sewage, hot tubs, air, soil, wheat and barley; there may be high incidence areas following disasters (ie. Sacramento floods and hurricane, "Hugo") Acanthamoeba: >7 species show ocular parasitology [A. castellani, A. quina, A. culbertsoni, A. lugdunesis, A. polyphaga, A. hatchetti, A. rysodes, A griffini] Note: Sequence types are recommended as much less ambiguous units of classification than currently used species names. Forms: cyst (sessile)*and trophozoite (motile) *makes the organism resistant to freezing, desiccation, standard chlorination and a variety of antimicrobial agents OCULAR INFECTION Clinical features-initial signs are non-specific; they include: patchy epithelial involvement (irregularity or pleomorphic focal or stellate epitheliopathy), suppurative/granulomatous or non-suppurative stromal keratitis, “bull’s eye” lesions, pseudo-guttata and iritis. More advanced signs include: a radial kerato-neuritis, ring infiltrate, nodular episcleritis, scleritis and hypopyon or hyphema; there may be a pseudo-membrane or adenopathy present. A remarkable lack of vascularization; often the only feature to help differentiating this infection from herpes simplex. Recently, early signs identified include a bull’s-eye lesion and the appearance of randomly distributed white spots on the cornea. Persistent epithelial defects immediately following penetrating keratoplasty may signal early amoebic infection. Symptomatology-usually unilateral pain disparate to ocular findings, often history to trauma +/or contact lens wear, symptoms generally wax and wane over time with chronicity. LABORATORY CONFIRMATION Corneal scrapings*- examined with Giemsa or tri-chrome stains, also culture with heated killed E. coli on non-nutrient agar or activated charcoal/yeast extract; other valuable tests include immunofluorescent techniques which include: calcofluor white and indirect immunofluorescent antibody testing. Standard culture negativity for bacteria, fungi, and virus expected. Cysts can sometimes be seen on soft lenses with high magnification. Confocal microscopy is an aid to early differential diagnosis. Polymerase chain reaction may be more sensitive than cultures as a diagnostic test. PCR analysis of the tears and epithelium may prove a useful tool in confirming an early diagnosis. *biopsy with intact epithelium or graft histology THERAPY Reported improvement*Antibiotic/Aminoglycoside: paromomycin (Humatin), neomycin Antifungal: clotrimazole, ketoconazole (Nizoral), itraconazole (Sporanox), miconazole (Monistat, Micatin), fluconazole (Diflucon) Antiparasitic/Aromatic Diamidine: propamidine isethionate (Brolene), hydroxystilbamidine (Pentamidine),hexamidine di-isethionate (Desomedine) Biocide/Cationic Antiseptic: polyhexamethylene biquanide (PHBG, Baquacil, Cosmocil), chlorhexidine digluconate, povidone-iodine (Betadine) *use one agent from at least two of the four categories above, plus oral ketoconazole or fluconazole, apply topicals every 30-60 minutes; for recalcitrants with significant ocular toxicity use drops in a three day cycle (hexamidine, paromomycin, and either PHBG or chlorhexidine) Supportive and adjunct therapy-debridement, conjunctival flaps, bandage lenses, debulking procedures, cryotherapy and steroids with caution**; grafts show a high recrudescence (NSAIDs seem to have little benefit in pain reduction when radial keratoneuritis is present) **inhibits metamorphogenesis Success has been reported by Seals (1995) using .02% chlorhexidine digluconate & .1% propamidine isethionate has been reported. CONTACT LENS RELATED RISK FACTORS/ PREVENTION Accouterment- use of distilled water, tap/well water*, or saliva; bacterial contamination of case and care system a common factor *recent concern especially with rigid lens wear Disinfection- some resistance to chemical disinfection Corneal trauma- hypoxia, mechanical trauma with lens wear Note: should avoid swimming and using hot tubs with contact lens wear ADDITIONAL PROTOZOAN Other amoeba- A similar infection may be caused by another amoeba besides Acanthamoeba, such as Naegleria, Hartmanella or Vahlkampfiid. Microsporidia- an obligate intracellular protozoan recently found on corneal scrapings of HIV infected patients from nasopharyngeal or urinary colonization. Generally it presents as a superficial punctate, multifocal keratitis (may be confined to the superficial cornea for months) in immuno-incompetent patients (genus-Encephalitozoon); a stromal keratitis is possible following trauma especially in immunocompetent individuals (genus- Nosema). A slight improvement has been noted with trimethoprim/sulfisoxazole. Recently itraconazole, propamidine isethionate, albendazole (benzimidazole), and especially topical fumagillin bicyclohexylammonium salt (Fumadil B), a bacteriostatic antibiotic secreted by Aspergillus, have shown some promise. Diagnosis is made by Gram’s stain, cytology with chromotrope-based stain, or by using electron or confocal microscopy. SELF ASSESSMENT QUIZ 1. T F Studies have shown that the majority of bacterial corneal ulcers in an outpatient setting are caused by gram + organisms. 2. T F Pseudomonas is the most common isolate responsible for ulcerative keratitis in contact lens wearers. 3. T F Microsporida infection is often associated with a punctate keratitis in HIV positive patients. 4. T F Most experts agree that contact lens related abrasions should not be patched. 5. T F Tetracaine is recommended for topical anesthesia when scraping the cornea as it is less bacteriostatic than proparacaine. 6. T F Sabourauds agar supports most fungi and yeast while inhibiting bacterial growth. 7. T F Regardless of the nature of the infecting agent, the cornea is usually best treated by frequent, topical application of antimicrobials. 8. T F The use of collagen shields has proven beneficial in delivering sustained concentration of antibiotics to the cornea and anterior chamber. 9. T F All the currently available fluoroquinolones are effective in treating keratitis regardless of the organism causing the disease. 10. T F Using a culturette tube is as effective as in-office plating on various media for retrieval and growth of microorganisms common to infection to contact lens wearers. 1. T 2. F 3. T 4. T 5. F 6. T 7. T 8. T 9. F 10. F Current Controversies In Managing Microbial Keratitis TRANSCRIPT QUALITY ASSESSMENT 1. Which of the following is not a risk factor for developing bacterial keratitis? A. B. C. D. ICU care the use of steroids sleeping with contact lenses aspirin therapy 2. In the landmark CLI relative risk study (extended wear) by Schein and co-workers, which of the following statement(s) is/are true? A. B. C. D. overnight wear is the overwhelming risk in contact lens wear smoking and aphakia are additional risk factors 24 million lens wearers are at risk A, B and C are correct 3. The following are symptoms or signs of corneal infection except: A. B. C. D. pain, redness and photophobia discharge and foreign body sensation anterior chamber reaction all are possible signs or symptoms of corneal infection 4. When culturing a presumed bacterial keratitis, the following media are generally plated: A. chocolate B. Sabouraud’s media C. non-nutrient agar D. A & C are correct 5. Which of the following is not a reason for mandatory culture? A. B. C. D. acute blepharitis dendritic ulcer dacryocystitis A &B are not considered mandatory reasons for culturing 6. There are many reasons to culture corneal ulcers. Which of the following is not one of them? A. should be a medico-legal component of your record in case the ulcer doesn’t respond to empiric treatment B. reveals sensitivities of the organism(s) C. no single agent is generally effective for most infections D. ineffectively treated organisms are difficult to isolate 7. Currently the most effective/complete treatment plan for resistant bacterial infection is: A. B. C. D. Vancomycin and Ceftazidime Tobrex and Ciloxan Gentamycin and Kefzol Ocuflox and Erythromycin 8. A patient with a severe corneal infection should be hospitalized if there is/are: A. B. C. D. inability of patient or family to deliver high frequency treatment inability to return initially for daily follow-up threatening perforation or significant scleral involvement all of the above are potential reasons requiring hospitalization 9. Which of the following statements is true regarding fungal keratitis? A. may account for over 40% of the corneal infections in some geographic area B. Natamycin is the only FDA approved drug for the treatment of fungal keratitis C. sub-conjunctival injections of Diflucon are started immediately upon first suspicion of yeast infection D. topical agents are rarely needed after the first week of treatment 10. Which of the following has generally not been used in the initial treatment acanthamoeba keratitis once a definitive diagnosis is made? A. B. C. D. anti-fungal agents (clotrimozole, ketoconazole, itraconazole) anti-parasitics (propamidine isethionate, hydroxystilbamidine) biocides (polyhexamethylene biquanide) all can be used for the initial treatment of acanthamoeba keratitis since it is often difficult to eradicate ANSWERS 1. D 2. D 3. D 4. D 5. D 6. D 7. A 8. D 9. B 10. D