Ocular infections associated with atypical mycobacteria: A review

Abstract

Atypical mycobacteria or non-tuberculous mycobacteria (NTM) are a group of acid-fast bacteria that are pathogenic to different parts of the eye. The organisms can cause a spectrum of ocular infections including keratitis, scleritis, uveitis, endophthalmitis and orbital cellulitis. Trauma, whether surgical or nonsurgical, has the highest correlation with development of this infection. Common surgeries after which these infections have been reported include laser in situ keratomileusis (LASIK) and scleral buckle surgery. The organism is noted to form biofilms with sequestration of the microbe at different inaccessible locations leading to high virulence. Collection of infective ocular material (corneal scraping/necrotic scleral tissue/abscess material/vitreous aspirate, etc.) and laboratory identification of the organism through microbiologic testing are vital for confirming presence of the infection and initiating treatment. In cluster infections, tracing the source of infection in the hospital setting via testing of different in-house samples is equally important to prevent further occurrences. Although the incidence of these infections is low, their presence can cause prolonged disease that may often be resistant to medical therapy alone. In this review, we describe the various types of NTM-ocular infections, their clinical presentation, laboratory diagnosis, management, and outcomes.

Figure 1

(Case 1) A patient who presented with history of pain, redness, and watering for 1 month duration. (a) At presentation, the patient showed a central epithelial defect with underlying dense, full-thickness corneal infiltrates surrounded by radiating stromal striae, giving a cracked windshield appearance. (b) Microbiologic investigation revealed atypical mycobacteria; the lesion resolved with scarring after 2 months of treatment with fortified vancomycin eye drops. Fortified vancomycin was started as the organism was resistant to other drugs, including amikacin. (Case 2) A 29-year-old man presented with history of pain, redness, watering of right eye of 1-month duration. (c) Slit-lamp picture at presentation showed a small area of infiltrate surrounded by an area of cellularity. (d) Picture after 1 month of starting fortified amikacin drops where the infiltrate started resolving. (e) Corneal scraping specimen stained with Ziehl–Neelsen stain, showing many inflammatory cells and acid-fast bacilli (pink color). (f) Ivory-colored, smooth colonies with elevated centers grown on the blood agar plate

Figure 2

Stepwise algorithmic approach for the diagnosis and management of non-tuberculous mycobacterial keratitis

Figure 3

Patient presented with a 6-month history of redness and severe pain, with secondary glaucoma. Examination showed granulomatous uveitis with endothelial exudate and an inferior scleral abscess. (a) The right eye 1 day after scleral biopsy and endo exudates scraping, air bubble and exudation in the anterior chamber, and inferiorly located scleral abscess. (b) The site of scleral involvement is covered with amniotic membrane. (c) Two weeks after starting therapy with fortified vancomycin eye drops; there is not much improvement and dense exudates are noted in the anterior chamber. (d) New lesion is noted nasally

Figure 4

Histopathology of atypical mycobacterial keratitis showing (a) loss of lamellar architecture (H and E, 8× original magnification); (b) ulcerated epithelium, destroyed Bowman’s membrane, and diffuse stromal infiltrates (H and E, 15× original magnification); (c) stromal infiltrates composed of lymphocytes, neutrophils, and plasma cells with ill-defined granuloma (arrow) (H and E, 40× original magnification). (d) Ulcer bed shows slender, beaded 20% acid-fast bacilli (inset) (Ziehl–Neelsen, 100× original magnification). Microbiology and histopathology of scleritis: (e) photomicrograph of smear from scleral scrapings shows scattered epithelial cells along with debris and thin, slender, and beaded bacilli (asterisk), which appear bright pink on Ziehl–Neelsen staining (100× original magnification); (f) scanner view of the scleral biopsy shows intact epithelium and underlying substantia propria with dense inflammatory infiltrates (H and E, 4× original magnification); (g) higher magnification image of aggregates of epithelioid cells forming granuloma (asterisk) admixed with neutrophils and blood vessels (H and E, 40× original magnification); (h) thin, slender, beaded acid-fast bacilli (red arrows) are noted in clusters and are also singly scattered (Ziehl–Neelsen, 100× original magnification). H and E = hematoxylin and eosin