Mycobacterium chelonei keratitis: report of a case and review of the literature

Abstract

Background: Mycobacterium (M) chelonei keratitis is a rare opportunistic eye infection that can cause significant morbidity when not being treated properly. The first case was documented by Gangadharam et al in 1978 and since then, a total of 49 cases were reported in the literature. One alarming fact is that more than 50% of cases were found in the Chinese population and mostly reported in recent years. The key to successful management of M. chelonei keratitis is early diagnosis by high index of suspicion. In order to alert ophthalmologists of this condition, we report a typical case of M. chelonei keratitis and review the literature of all the reported cases with special reference to its risk factors, treatments and outcome.

Methods: The cases reported in the literature and a case of our own were reviewed and analyzed.

Results: Our case was a 42-year-old gentleman who developed M. chelonei keratitis following pterygium surgery. He had typical clinical features of irregular infiltrates with radiating projections, indistinct fluffy lesion margins, satellite lesions and associated epithelial defect. Penetrating keratoplasty was performed after failed medical treatments. He recovered fully with a best corrected visual acuity (BCVA) of 20/30 at 24 months after the corneal transplant. A total of 49 cases were reported in the literature. The major risk factor was corneal injury, including surgical trauma. Corneal foreign bodies (24 cases, 48%) were found to be highly correlated, especially metallic foreign bodies (16 cases, 32%). Diagnosis was usually delayed for weeks or months and medical treatment alone often failed. Amikacin is usually the treatment of choice but its efficacy is just sub-optimal. Multi-resistance to the commonly used board spectrum antibiotics is not uncommon. The drug sensitivity test against atypical mycobacterium is technically difficult to perform and in vitro results are well known to be poorly related to clinical response. Combined extirpative keratectomy and topical antibiotics had been tried and was shown to be effective. Penetrating keratoplasty appeared to be a good definitive treatment for drug-resistance and advanced cases.

Conclusion: M. chelonei keratitis is a rare opportunistic infection. The major risk factor is eye injury, with foreign bodies or surgical trauma. Diagnosis is often missed and delayed as a result of its scarcity and variable presentations. High index of clinical suspicion with early diagnosis and prompt combined medical and surgical intervention seem to be the best measure to decrease ocular morbidity. Good alertness and knowledge of this condition would help our patients in the Far East as the literature review has shown a recent trend of increase in frequency and more than 50% of the reported cases come from the Chinese patients.