Actinomyces bowdenii ulcerative keratitis in a dog

A 5-year-old spayed female diabetic mixed-breed dog underwent phacoemulsification and intraocular lens implantation to correct bilateral hypermature cataracts. Two months postsurgery, the patient presented with ulcerative keratitis and multifocal stromal abscessation OD, which was controlled, but never resolved, with topical fluoroquinolone therapy. The patient re-presented 2 months later with a new, raised, white gritty corneal opacity associated with hyperemia, chemosis, and blepharospasm OD. Cytology of the right cornea revealed filamentous bacteria, suggestive of Actinomyces spp. Actinomyces bowdenii was subsequently isolated in pure culture and identified via 16s rDNA sequencing. Actinomyces bowdenii has never before been described as a cause of ocular infection. An immunosuppressed corneal environment likely contributed to this opportunistic Actinomycosis. The infection was not controlled with fluoroquinolone therapy, and the isolate, in vitro, was resistant to three fluoroquinolones (ciprofloxacin, ofloxacin, and levofloxacin), which also has not been previously reported for this species of Actinomyces. A superficial keratectomy with conjunctival graft was employed to successfully manage the infection.