Close
New

Medscape is available in 5 Language Editions – Choose your Edition here.

 

Bacterial Keratitis Workup

  • Author: Fernando H Murillo-Lopez, MD; Chief Editor: Hampton Roy, Sr, MD  more...
 
Updated: Aug 28, 2014
 

Laboratory Studies

See the list below:

  • Scrapings of the corneal ulcer, including the edges, should be obtained using a sterile spatula or blade, and they should be plated in chocolate, blood, and Sabouraud agar plates.
  • Microscope slides are used for stained smears with Gram, Giemsa, and acid-fast stain or acridine orange/calcofluor white (if fungi or Acanthamoeba are suspected).
  • Samples of the eyelids/conjunctiva, topical ocular medications, contact lens cases, and solutions also may be cultured.
  • If the patient has been treated partially and the keratitis is mild or moderately severe, antibiotic therapy can be suspended for 12 hours before obtaining corneal/conjunctival samples for culture and sensitivity, to increase the yield of a positive culture.
  • Cotton swabs contain fatty acids, which have an inhibitory effect on bacterial growth. On the other hand, calcium alginate moistened with trypticase soy broth can be used to obtain culture material to inoculate directly onto the culture media.
  • Topical anesthetic (proparacaine hydrochloride 0.5%) should be used to anesthetize the patient prior to culture scraping because it has the least inhibitory effect. In contrast, tetracaine and cocaine have bacteriostatic effects.
  • Repeat cultures can be obtained if the original cultures were negative and the ulcer is not improving clinically.
  • 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.
Next

Imaging Studies

See the list below:

  • 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.
Previous
Next

Procedures

See the list below:

  • Corneal biopsy: A deep lamellar excision can be made using a disposable skin punch or a small Elliott corneal trephine. The superficial cornea is incised and deepened with a surgical blade to approximately 200 microns. Then, a lamellar dissection is performed, and the material is plated directly onto culture media. A portion also can be sent for histopathologic evaluation.
Previous
Next

Histologic Findings

During the initial stages, the epithelium and the stroma in the area of injury and infection swell and undergo necrosis. Acute inflammatory cells (mainly neutrophils) surround the beginning ulcer and cause necrosis of the stromal lamellae. In cases of severe inflammation, a deep ulcer and a deep stromal abscess may coalesce, resulting in thinning of the cornea and sloughing of the infected stroma.

As the natural host defense mechanisms overcome the infection, humoral and cellular immune defenses combine with antibacterial therapy to retard bacterial replication. Following this process, phagocytosis of the organism and cellular debris take place, without further destruction of stromal collagen. During this stage, a distinct demarcation line may appear as the epithelial ulceration and stromal infiltration consolidate and the edges become rounded.

Vascularization of the cornea may follow if the keratitis becomes chronic. In the healing stage, the epithelium resurfaces the central area of ulceration and the necrotic stroma is replaced by scar tissue produced by fibroblasts. The reparative fibroblasts are derived from histiocytes and keratocytes that have undergone transformation. Areas of stromal thinning may be replaced partially by fibrous tissue. New blood vessel growth directed toward the area of ulceration occurs with delivery of humoral and cellular components to promote further healing. The Bowman layer does not regenerate but is replaced with fibrous tissue.

New epithelium slowly resurfaces the irregular base, and vascularization gradually disappears. With severe bacterial keratitis, the progressive stage advances beyond the point in which the regressive stage can lead to the healing stage. In such severe ulcerations, stromal keratolysis may progress to corneal perforation. Uveal blood vessels may participate in sealing the perforation, resulting in an adherent vascularized leukoma.

Previous
 
 
Contributor Information and Disclosures
Author

Fernando H Murillo-Lopez, MD Senior Surgeon, Unidad Privada de Oftalmologia CEMES

Fernando H Murillo-Lopez, MD is a member of the following medical societies: American Academy of Ophthalmology

Disclosure: Nothing to disclose.

Specialty Editor Board

Simon K Law, MD, PharmD Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine

Simon K Law, MD, PharmD is a member of the following medical societies: American Academy of Ophthalmology, Association for Research in Vision and Ophthalmology, American Glaucoma Society

Disclosure: Nothing to disclose.

Christopher J Rapuano, MD Professor, Department of Ophthalmology, Jefferson Medical College of Thomas Jefferson University; Director of the Cornea Service, Co-Director of Refractive Surgery Department, Wills Eye Hospital

Christopher J Rapuano, MD is a member of the following medical societies: American Academy of Ophthalmology, American Ophthalmological Society, American Society of Cataract and Refractive Surgery, Contact Lens Association of Ophthalmologists, International Society of Refractive Surgery, Cornea Society, Eye Bank Association of America

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cornea Society, Allergan, Bausch & Lomb, Bio-Tissue, Shire, TearScience, TearLab<br/>Serve(d) as a speaker or a member of a speakers bureau for: Allergan, Bausch & Lomb, Bio-Tissue, TearScience.

Chief Editor

Hampton Roy, Sr, MD Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences

Hampton Roy, Sr, MD is a member of the following medical societies: American Academy of Ophthalmology, American College of Surgeons, Pan-American Association of Ophthalmology

Disclosure: Nothing to disclose.

Additional Contributors

Jack L Wilson, PhD Distinguished Professor, Department of Anatomy and Neurobiology, University of Tennessee Health Science Center College of Medicine

Jack L Wilson, PhD is a member of the following medical societies: American Association of Anatomists, American Heart Association, American Association of Clinical Anatomists

Disclosure: Nothing to disclose.

References
  1. Hall BJ, Jones L. Contact Lens Cases: The Missing Link in Contact Lens Safety?. Eye Contact Lens. 2010 Jan 19. [Medline].

  2. Khan YA, Kashiwabuchi RT, Martins SA, Castro-Combs JM, Kalyani S, Stanley P. Riboflavin and ultraviolet light a therapy as an adjuvant treatment for medically refractive acanthamoeba keratitis report of 3 cases. Ophthalmology. 2011 Feb. 118(2):324-31. [Medline].

  3. Haas W, Pillar CM, Torres M, Morris TW, Sahm DF. Monitoring Antibiotic Resistance in Ocular Microorganisms: Results From the Antibiotic Resistance Monitoring in Ocular MicRorganisms (ARMOR) 2009 Surveillance Study. Am J Ophthalmol. 2011 Oct. 152(4):567-574.e3. [Medline].

  4. Lalitha P, Srinivasan M, Manikandan P, Bharathi MJ, Rajaraman R, Ravindran M, et al. Relationship of In Vitro Susceptibility to Moxifloxacin and In Vivo Clinical Outcome in Bacterial Keratitis. Clin Infect Dis. 2012 Mar 23. [Medline].

  5. Bower KS, Kowalski RP, Gordon YJ. Fluoroquinolones in the treatment of bacterial keratitis. Am J Ophthalmol. 1996 Jun. 121(6):712-5. [Medline].

  6. Caballero AR, Marquart ME, O'Callaghan RJ, Thibodeaux BA, Johnston KH, Dajcs JJ. Effectiveness of fluoroquinolones against Mycobacterium abscessus in vivo. Curr Eye Res. 2006 Jan. 31(1):23-9. [Medline].

  7. Genvert GI, Cohen EJ, Donnenfeld ED. Erythema multiforme after use of topical sulfacetamide. Am J Ophthalmol. 1985 Apr 15. 99(4):465-8. [Medline].

  8. Goldstein MH, Kowalski RP, Gordon YJ. Emerging fluoroquinolone resistance in bacterial keratitis: a 5-year review. Ophthalmology. 1999 Jul. 106(7):1313-8. [Medline].

  9. Hirst LW, Harrison GK, Merz WG. Nocardia asteroides keratitis. Br J Ophthalmol. 1979 Jun. 63(6):449-54. [Medline].

  10. Hirst LW, Smiddy WE, Stark WJ. Corneal perforations. Changing methods of treatment, 1960--1980. Ophthalmology. 1982 Jun. 89(6):630-5. [Medline].

  11. Hyndiuk RA, Eiferman RA, Caldwell DR. Comparison of ciprofloxacin ophthalmic solution 0.3% to fortified tobramycin-cefazolin in treating bacterial corneal ulcers. Ciprofloxacin Bacterial Keratitis Study Group. Ophthalmology. 1996 Nov. 103(11):1854-62; discussion 1862-3. [Medline].

  12. Knapp A, Stern GA, Hood CI. Mycobacterium avium-intracellulare corneal ulcer. Cornea. 1987. 6(3):175-80. [Medline].

  13. Leibowitz HM. Clinical evaluation of ciprofloxacin 0.3% ophthalmic solution for treatment of bacterial keratitis. Am J Ophthalmol. 1991 Oct. 112(4 Suppl):34S-47S. [Medline].

  14. Moore MB, Newton C, Kaufman HE. Chronic keratitis caused by Mycobacterium gordonae. Am J Ophthalmol. 1986 Oct 15. 102(4):516-21. [Medline].

  15. Newman PE, Goodman RA, Waring GO 3d. A cluster of cases of Mycobacterium chelonei keratitis associated with outpatient office procedures. Am J Ophthalmol. 1984 Mar. 97(3):344-8. [Medline].

  16. Parmar P, Salman A, Kalavathy CM. Comparison of topical gatifloxacin 0.3% and ciprofloxacin 0.3% for the treatment of bacterial keratitis. Am J Ophthalmol. 2006 Feb. 141(2):282-286. [Medline].

  17. Pate JC, Jones DB, Wilhelmus KR. Prevalence and spectrum of bacterial co-infection during fungal keratitis. Br J Ophthalmol. 2006 Mar. 90(3):289-92. [Medline].

  18. Poggio EC, Glynn RJ, Schein OD. The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med. 1989 Sep 21. 321(12):779-83. [Medline].

  19. Schein OD, Glynn RJ, Poggio EC. The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. A case-control study. Microbial Keratitis Study Group. N Engl J Med. 1989 Sep 21. 321(12):773-8. [Medline].

  20. Schlech BA, Alfonso E. Overview of the potency of moxifloxacin ophthalmic solution 0.5% (VIGAMOX). Surv Ophthalmol. 2005 Nov. 50 Suppl 1:S7-15. [Medline].

  21. Stern GA, Buttross M. Use of corticosteroids in combination with antimicrobial drugs in the treatment of infectious corneal disease. Ophthalmology. 1991 Jun. 98(6):847-53. [Medline].

  22. Stern GA, Schemmer GB, Farber RD. Effect of topical antibiotic solutions on corneal epithelial wound healing. Arch Ophthalmol. 1983 Apr. 101(4):644-7. [Medline].

  23. Varma R, eds. Cornea/external diseases. Essentials of Eye Care: The Johns Hopkins Wilmer Handbook. Lippincott Williams & Wilkins. 1997:152-203.

 
Previous
Next
 
Human eye anatomy.
 
 
 
All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.