Clinical Case Report - Mycobacterium fortuitum keratitis.

By Ruben Sanchez, MD

Doheny Eye Institute, University of Southern California

Chief Complaint: “My left eye is red and hurts”

History of Present Illness: 46 year-old Asian female presented with a two week history of red, painful left eye (OS) with decreased vision OS. The patient states that one week prior to evaluation, she saw an outside ophthalmologist who diagnosed her with an “ulcer” and was started on oral Acyclovir, Vigamox and Pred-Forte drops. The patient states no relief of symptoms despite therapy.

Past Medical History: Unremarkable

Past Ocular History: Mild hyperopia. The patient denies contact lens wear or trauma to OS.

Medications: None

Allergies: No known drug allergies.

Best-Corrected Visual Acuity: 20/30 (right eye -OD), 20/100 (left eye -OS)

Pupils: Pharmacologically dilated OS

Intraocular Pressures: 12 mmHg OD, 33 mmHg OS

Ductions: Full in both eyes (OU)

Slit Lamp Examination:

• Lids/Lashes/Lacrimal Glands: 2+ Scurf OS, 1+ Meibomian Gland Dysfunction OS
• Conjunctiva/Sclera: 4+ Injection OS
• Cornea: Epithelial defect with ulcer OS, 1+ corneal edema OS, small keratoprecipitates OS (Figure 1).
• Anterior Chamber: 40% formed hypopyon OS (Figure 2).

Figure 1. Slit lamp biomicrosopy OS with topical fluorescein and cobalt blue filter. Note epithelial defect with ulcer OS.










Figure 2. Slit lamp biomicrosopy OS. Note 40% formed hypopyon in anterior chamber.

Review of Systems: Denied any trauma from vegetable matter, past soft contact lens use or history of herpetic keratitis.

Corneal Scrapings & Culture: 2+ Acid Fast Bacilli that was later identified as Mycobacterium fortuitum.

Discussion:

Mycobacterium fortuitum keratitis was first described by Turner and Stintson in 1965 following removal of a superficial corneal foreign body. This organism is second only to Mycobacterium chelonae as the most commonly implicated cause of nontuberculous mycobacterial keratitis. This organism is ubiquitous and found in municipal, tap, distilled lab and operating room waters, soil and milk. Perhaps most alarming of all, this organism is resistant to chlorine. Antecedent ocular trauma was reported in 3% of cases.

Of note, 50% of patients who developed Mycobacterium fortuitum keratitis report previous ocular surgery ranging from penetrating keratoplasty to simple outpatient procedures that include: radial keratotomy; pterygium removal; cataract extraction and laser-assisted in situ keratomileusis (LASIK). Many case reports describe flap-related infection following LASIK. It is important to understand that LASIK utilizes aseptic but not completely sterile techniques. Specifically, the motor compartment of the microkeratome can not be autoclaved. Treatment is difficult as Mycobacterium fortuitum keratitis is usually resistant to anti-mycobacterial agents such as Amikacin, Ethambutol, Isoniazid, Rifampin and Streptomycin. Therefore, the American Academy of Ophthalmology currently recommends treatment with Clarithromycin (10 mg/ml) and Moxifloxacin (5mg/mL) or Gatifloxacin (3mg/mL). Despite these treatment modalities Mycobacterium fortuitum keratitis has an indolent and recalcitrant course that frequently results in corneal scarring and a poor visual outcome.

Diagnosis: Mycobacterium fortuitum keratitis

Differential Diagnosis: Fungal keratitis, Acanthoemeba keratitis, Herpes simplex keratitis

References:

• Abshire R, Cockrum P, Crider J, Schlech B. Topical antibacterial therapy for mycobacterial keratitis: potential for surgical prophylaxis and treatment. Clin Ther. 2004 Feb;26(2):191-6.

• Hyon JY, Joo MJ, Hose S, Sinha D, Dick JD, O'Brien TP. Comparative efficacy of topical gatifloxacin with ciprofloxacin, amikacin, and clarithromycin in the treatment of experimental Mycobacterium chelonae keratitis. Arch Ophthalmol. 2004 Aug;122(8):1166-9.

• John T and Velotta E. Nontuberculous (Atypical) Mycobacterial Keratitis After LASIK: Current Status and Clinical Implications. Cornea. 24(3):245-255, April 2005.

• Kinota S, Wong KW, Biswas J, Rao NA. Changing patterns of infectious keratitis: Overview of clinical and histopathologic features of keratitis due to acanthamoeba or atypical mycobacteria, and of infectious crystalline keratopathy. Current Ophthalmology. 1993;41(1):3-14.

• Turner L, Stinson I. Mycobacterium fortuitum as a cause of corneal ulcer. Am J Ophthalmol. 1965;60:329–331.