Nocardia transvalensis resistant to amikacin: an unusual cause of microbial keratitis

To report a case of microbial keratitis caused by Nocardia transvalensis with resistance to amikacin.

Case report.

A 51-year-old man was referred with a 10-week history of ocular pain, photophobia, redness, and blurred vision. At his initial presentation, a corneal foreign body was removed and he was diagnosed with anterior uveitis, with commencement of topical corticosteroid therapy and ofloxacin. Despite treatment, he experienced ongoing foreign body sensation and glare. At presentation to our clinic, a central epithelial defect with multiple stromal infiltrates in a wreath pattern was identified and a diagnosis of infective keratitis was made. He was initially commenced on topical amikacin, oral trimethoprim-sulfamethoxazole, and oral voriconazole. Corneal scraping confirmed Nocardia species. Microbiological culture revealed N. transvalensis as the causative organism, with resistance to several antibiotics, including amikacin. Clinically, there was only partial response of the keratitis to initial therapy. Treatment was changed to oral trimethoprim-sulfamethoxazole and topical ciprofloxacin, with eventual clinical improvement.

This is the first reported case of N. transvalensis keratitis. In patients with Nocardia keratitis and only partial response to amikacin treatment, this isolate should be considered as it is resistant to aminoglycoside antibiotics.