Mycobacterium chelonei masquerading as Corynebacterium in a case of infectious keratitis: A diagnostic dilemma

Purpose. The diagnosis of Mycobacterium keratitis can often be missed both clinically and microbiologically and this report highlights one such case. Methods, Review of medical and microbiological records. Results, We report a case of Mycobacterium keratitis in a 25-year-old man that was misdiagnosed as Corynebacterium keratitis at initial presentation. presence of partially stained and beaded bacilli in a Gram-stained smear of repeat corneal scrapings raised the suspicion of an unusual organism. Ziehl-Neelsen staining of the decolorized Gram-stained smear and subculture on Lowenstein-Jensen medium helped us to establish the diagnosis. Conclusions, A high degree of suspicion needs to be maintained, especially in cases in which (a) there is a history of corneal trauma involving a foreign body, (b) the Gram-stained smear of corneal scrapings shows a paucity of organisms and the presence of partially stained and beaded bacilli in the presence of confluent growth of colonies resembling those of Corynebacterium, and (c) a typical corneal feature like "cracked windshield" stromal lesion is seen, to avoid such a misdiagnosis. Inclusion of a Lowenstein-Jensen culture at the initial presentation, especially when the clinical presentation is atypical, as seen in this case, will lead to an early diagnosis.