Mycobacterium chelonae in a tectonic corneal graft.

Atypical mycobacterial infections of the cornea can present with nonspecific inflammatory changes and graft rejection, with no obvious focus to culture and a subsequent delay to diagnosis. These pathogens are well documented in the literature following laser-assisted in situ keratomileusis but have rarely been described following corneal transplant surgery. We report a single case of Mycobacterium chelonae keratitis 1 year after tectonic keratoplasty.

Introduction

Atypical mycobacterial infections from organisms such as Mycobacterium chelonae have been well documented in the literature following laser-assisted in situ keratomileusis (LASIK).[12] However, it is not until recently that there have been further reports of the involvement of this pathogen in a patient with Sjogren's syndrome[3] and no other apparent risk factors and also following corneal graft surgery for a range of indications,[45] manifesting almost three decades posttransplant.[6] We present a case of M. chelonae keratitis occurring 1 year after tectonic keratoplasty.

Case Report

A 71-year-old male presented to our Emergency Department with a short history of reduced vision and pain in the left eye. His only known previous ophthalmic history was of corneal foreign body removal 45 years previously although previous medical history included peripheral vascular disease, ischemic heart disease, chronic obstructive pulmonary disease, and osteoporotic vertebral fractures. Initial ophthalmic assessment revealed vision of light perception only, with an inferior descemetocoele and positive Seidel test. His right eye was unremarkable with no evident corneal pathology. Emergency tectonic keratoplasty was performed and culture of samples taken at the time of surgery revealed skin flora only. Recovery following tectonic keratoplasty was complicated by a nonhealing epithelial defect which necessitated an amniotic membrane graft. Eight months following surgery, the patient developed a graft rejection episode; poor concordance with topical steroid medication being a likely contributing factor.

Four weeks following this rejection episode, he presented again with a painful, injected left eye. Visual acuity remained at hand movements only. Anterior segment examination revealed a large, central, white corneal infiltrate within the tectonic keratoplasty [Figure 1]. A 1 mm hypopyon was present. An initial corneal scrape failed to identify a causative pathogen, and there was no clinical response to topical antibacterial and antifungal medication. A further corneal scrape revealed tiny, fine colonies of long Gram-positive rods [Figure 2], consistent with mycobacteria. Subsequent auramine phenol staining was positive. Line probe assay of mycobacterial genetic material (Genotype Mycobacterium CM, Hain Lifescience) was performed, which resulted in the diagnosis of M. chelonae.

Figure 1

Anterior segment photograph

Figure 2

Gram-stain

Treatment was commenced with topical cefuroxime, amikacin, and gentamicin supplemented by oral linezolid. Following 1 month of therapy, an epithelial plaque and significant scarring remained, so the patient underwent further therapeutic penetrating keratoplasty. This was complicated further by postoperative hyphema and recurrence 1 month later of the endothelial plaque, suggestive of recurrence of M chelonae infection. Anterior chamber washout with culture of washings was negative for acid-fast bacilli. The patient retains light perception vision and is being managed for chronic epithelial defect in the corneal graft.

Discussion

M. chelonae are nontuberculous mycobacteria classified in the rapidly growing mycobacteria subgroup. They are present throughout our environment and have been isolated from both natural and distilled water sources with resistance to chlorine and some common hospital grade detergents such as glutaraldehyde.[7] Sources of infection include household water heaters due to the stagnant nature of the water and optimized growth temperatures.[8]

It frequently infects the skin in the form of a cellulitis or more disseminated disease having first colonized the skin flora with subsequent skin trauma facilitating cutaneous invasion.[9]

The organism is known to cause dacryocystitis, canaliculitis, conjunctivitis, scleritis, endophthalmitis, and keratitis;[10] making the eye the second most common site of infection. Risk factors for infection include trauma, LASIK, and all procedures involving retained biomaterial.[11] Additional risk factors include the presence of contact lens, corticosteroid use, and human immunodeficiency virus infection.

Atypical mycobacterial infections of the cornea can often present initially with mild nonspecific inflammatory changes and graft rejection. Because there is often no obvious focus to culture, a subsequent delay to diagnosis can result. It is likely that our patient developed an infection from contact from a contaminated water source or subsequent skin surface lid colonization following acute graft rejection and the accompanying topical and subconjunctival steroids, he received.

To the best of our knowledge, this is one of the first cases of M. chelonae keratitis reported following tectonic corneal graft. This presentation emphasizes the importance of having a high index of suspicion when presented with nonresolving inflammation or graft rejection in corneal transplant patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.