An alternative explanation for the origin of this infection is that the patient harbored mycobacterial organisms in his conjunctiva prior to vitrectomy. Radiation therapy, and perhaps other topical therapies, could have predisposed the conjunctiva to opportunistic infection or colonization by mycobacterial organisms. Although white and quiet at the time of vitrectomy, our patient's conjunctiva, which was chronically inflamed for more than 6 months prior to surgery, cannot be discounted as the potential source of the infection. The optimal therapy for nontuberculous mycobacterial infections is not known. Amikacin has been the single most frequently used antibiotic for atypical mycobacterial infection, but some patients fail to respond to topical therapy.
Some nontuberculous mycobacteria demonstrate in vitro resistance to ciprofloxacin.
4 Topical ciprofloxacin may be more effective against M fortuitum than M chelonae . 17 Animal models of atypical mycobacterial keratitis have shown that topical ciprofloxacin can effectively reduce the number of organisms and infiltrate size, but these findings are more consistently demonstrated for M fortuitum than M chelonae . 19-22 Animal models have also suggested that multiple topical drugs do not improve effectiveness. 19 Single-agent treatment, however, may be more likely to fail because of the development of drug resistance. In one series, clarithromycin had the best in vitro sensitivity profile against nontuberculous mycobacteria.