Unusual anaerobic bacteria in keratitis after laser in situ keratomileusis: diagnosis using molecular biology methods

Laser in situ keratomileusis (LASIK) was performed in the left eye of a 57-year-old man for residual ametropia after phacoemulsification. The patient was given topical tobramycin and a corticosteroid for 1 week postoperatively. Fifteen days later, he developed 3 corneal infiltrates beneath the flap with a gas bubble, suggesting an anaerobic infection. Tobramycin and ofloxacin were administered every 2 hours, but the condition worsened. Corneal scrapings were taken from beneath the flap for microbiological cultures and a polymerase chain reaction (PCR) test. The PCR amplification was negative for fungi and mycobacteria and positive for bacterial DNA. Sequence analysis showed Propionibacterium granulosum as the causal agent, but cultures were negative. Treatment with vancomycin and cefazolin led to clinical improvement, with resolution of corneal infiltrates. Anaerobic microorganisms can cause keratitis after LASIK. Polymerase chain reaction amplification and DNA typing can help detect microorganisms involved in these ocular infections.