Spectrum and clinicomicrobiological profile of Nocardia keratitis caused by rare species of Nocardia identified by 16S rRNA gene sequencing

Abstract

Purpose To report the predisposing factors, clinical profile, and treatment outcome of patients with keratitis that was caused by a rare species of Nocardia. Methods Between April 2006 and October 2008, medical and microbiology records of patients with keratitis that was caused by Nocardiawere reviewed. Isolates were identified to species level by 16S rRNAgene sequencing, and antibiotic susceptibility testing was performed by E-test to amikacin, azithromycin, clarithromycin, ciprofloxacin, gatifloxacin, and tobramycin. Results Of 19 cases with Nocardiakeratitis, 8 were caused by unusual isolates. Species distribution among the eight isolates was as follows: the Nocardia levis (2 of 8), Nocardia amamiensis (2 of 8), Nocardia abscessus (1 of 8), Nocardia puris (1 of 8), Nocardia beijingensis (1 of 8), and Nocardia thailandica (1 of 8). All eight (100%) isolates were sensitive to amikacin and tobramycin. Trauma to the cornea was the major predisposing factor in seven of the eight patients. Five patients presented with the characteristic wreath-pattern infiltrate. The infection resolved to topical therapy with amikacin sulphate (2.5%) in six patients, whereas two patients treated with the same antibiotic were lost to follow-up at a point when the lesion was showing signs of resolution. Conclusion The healing response in Nocardiakeratitis cases was the same, irrespective of species.