Ocular mycobacteriosis-dual infection of M. tuberculosis complex with M. fortuitum and M. bovis

Background: We report unfavorable outcome in a patient with subretinal granuloma caused by dual infection of Mycobacterium tuberculosis complex with Mycobacterium fortuitum and Mycobacterium bovis in an immunosuppressed, non-HIV patient. We did a systematic review of literature on dual infection due to M. tuberculosis and M. fortuitum via MEDLINE and PUBMED and could not find any case reported of causing this kind of dual infection in the eye.

Results: A 38-year-old Indian male patient presented with decreased vision in the left eye for 3 months, diagnosed as tubercular choroidal granuloma with associated retinal angiomatosis proliferans (RAP) lesion. He also had multiple enlarged lymph nodes in the chest, and sternal pus sample was positive for acid-fast bacilli (AFB). M. tuberculosis complex was detected by gene expert. The patient was started on antitubercular treatment (ATT) whereby the lung lesions improved but the ocular lesion showed initial clinical improvement followed by worsening. Twenty-five-gauge diagnostic pars plana core vitreous surgery was done whereby sample demonstrated a large number of AFB on Ziehl-Neelsen stain and auramine-rhodamine stain. The vitreous sample showed growth on routinely inoculated mycobacteria growth indicator tube (MGIT) 960 tubes, and multiplex polymerase chain reaction (PCR), Gene Xpert MTB/ RIF assay (Cepheid, Sunnyvale, CA), and line probe assay (LPA) were positive for ocular tuberculosis. In view of nonresponse to conventional ATT, a suspicion of dual infection of M. tuberculosis complex with a nontubercular mycobacteria was kept and a subculture was made onto the solid Lowenstein-Jensen (LJ) medium from the positive MGIT 960 tubes. Two morphologically distinct types of colonies were obtained on LJ slopes. Subsequently, the two etiological agents were identified as M. fortuitum and M. bovis by PCR from the vitreous sample.

Conclusions: Co-infection of M. tuberculosis complex with nontubercular mycobacterium (NTM) has never been reported from ocular tuberculosis before. In immunosuppressed individuals, who test positive for MTB, not responding to the standard ATT, one needs to have a high index of clinical suspicion to rule out associated NTM infection and initiate appropriate multidrug systemic antibiotic therapy early.