Nocardia keratitis: species, drug sensitivities, and clinical correlation

To correlate the clinical presentation and treatment outcome of Nocardia keratitis with the time to diagnosis, different species and with the drug sensitivity pattern.

Patients with Nocardia corneal ulcers were studied at a tertiary eye care center. Speciation of Nocardia isolates was done by sequencing the 16s rRNA gene. Clinical response to treatment was assessed by chart review.

Twenty one (65.3%) patients presented within 15 days of the onset of symptoms with typical clinical features of Nocardia keratitis, ie, a ring-like distribution of superficial infiltrates in a wreath pattern. Eight patients (25%) who presented after 15 days and within 30 days had an ulcer resembling fungal keratitis. N. Cyriacigeorgica (n = 11; 34.37%), N. asteroides (n = 9; 28%), N. farcinica (n = 7; 22%,) and N. Otitidiscaviarum (n = 5; 16%). All the species had 100% sensitivity to amikacin, sulphamethoxazole, imipenem and co-trimoxazole. Time to diagnosis of the infection was significantly associated with the different types of clinical presentation; those presenting early having the typical clinical picture (P = 0.004). Patients (73%) presenting within 15 days showed a highest recovery rate. (P = 0.045). The recovery time of the patients when compared with species showed those who were infected with N. cyriageorgica had a healing time of less than 15 days. Clinically, healing was faster when treated with 2% amikacin. Visual outcome improved in fourteen patients (44%) and sixteen (50%) patients remained the same (P = 0.0001).

Characteristic clinical picture of Nocardia is dependant on early presentation. It could be mistaken for fungal keratitis. Microbiological confirmation is important. Drug of choice for Nocardia keratitis is amikacin.