Confocal microscopy for Nocardia keratitis.

PURPOSE

To assess the role of confocal microscopy for in vivo detection of Nocardia in patients with microbial keratitis.

DESIGN

Retrospective interventional case series.

PARTICIPANTS

Three patients with microbiologically proven Nocardia keratitis.

INTERVENTION

Confocal microscopy.

METHODS

We performed confocal microscopy in microbiologically proven cases of Nocardia asteroides keratitis. A masked observer examined the images. For better understanding of the images, we also performed confocal microscopy on a blood agar culture plate with Nocardia growth.

RESULTS

Confocal microscopy of infiltrated cornea revealed highly reflective, short, thin branching filaments with bright inflammatory cells in the background. The filaments were seen clearly at the edge of the infiltrate. In scans with faint images, these filaments became more visible on inversion of bright and dark components. Confocal microscopy of cultured organisms also revealed filamentous beaded structures with a morphology identical to that of those seen in vivo.

CONCLUSION

Nocardia, a filamentous bacterium, produces a distinct image on confocal microscopy. This in vivo examination technique may be useful in cases of deep-seated infiltrates where routine microbiology workup does not yield positive results.