Predatory Bacteria can Reduce Pseudomonas aeruginosa Induced Corneal Perforation and Proliferation in a Rabbit Keratitis Model.

Purpose: Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included. Methods: Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic Δ lasR mutant and co-injected with PBS or B. bacteriovorus . After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines. Results: We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n=24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n=25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The Δ lasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus . Conclusion: These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Development of Corneal Sensation With Remodeling of the Epithelium and the Palisades of Vogt After Corneal Neurotization.

PURPOSE: Neurotrophic keratopathy (NK) produces persistent epithelial erosion which is hard to treat effectively. Recently, corneal neurotization surgery has produced reinnervation of the cornea with resolving neurotrophic keratopathy. We hypothesized that the generation of corneal epithelial nerves after neurotization surgery would not only restore the integrity of corneal epithelium but also produce a change in the configuration of the palisades of Vogt (POV), which houses the corneal epithelial stem cells. METHODS: We assessed a patient with unilateral congenital corneal anesthesia with optical coherence tomography pre-neurotization and post-neurotization. RESULTS: Over the course of 2 years, the patient gained corneal epithelial sensation and corneal and limbal epithelium was restored to normal thickness with corresponding changes in the POV. CONCLUSIONS: The intimate relationship between epithelium and sensory nerves of the cornea has been well documented; however, changes in the corneal epithelial stem cell niche in conjunction with development of innervation have not previously been reported. Considering the architecture of the corneal nerves in conjunction with the architecture of the POV may assist in developing treatments that can support the regeneration and maintenance of epithelium during nerve regeneration.

Optical Coherence Tomography Imaging of the Palisades of Vogt to Assist Clinical Evaluation and Surgical Planning in a Case of Limbal Stem-Cell Deficiency.

PURPOSE: To describe the use of volumetric optical coherence tomography (OCT) imaging to assist evaluation of a patient referred for autologous limbal stem-cell transplant. METHODS: This is a case report of a 50-year-old patient presenting with unilateral limbal stem-cell deficiency who was referred for autologous limbal stem-cell transplant. The presence of Salzmann nodules in the donor eye raised questions about the efficacy of transplantation, prompting examination of both eyes using volumetric OCT imaging to determine whether there were palisades of Vogt (POV) present. Image volumes were acquired in all clock hours and were compared against those of an age-matched normal subject. RESULTS: Palisades were found in both eyes, although in both eyes there were fewer palisade ridges, and those that were present were not as distinct as those of the normal subject. The OCT volumes also showed that stromal scarring was present only in the anterior stroma of the intended transplant eye. These findings suggested that the patient may be able to sustain a deep anterior lamellar keratoplasty without an autologous transplant, which would spare any insult to the opposing eye and require less surgery to restore vision in the affected eye. Nine months postsurgical follow-up revealed significant improvement in visual acuity and no scar tissue development. CONCLUSION: The OCT evaluation of the POV provides detailed information to the clinician that may assist in diagnosis and evaluation of patients before transplantation. Further development of this technique is necessary to make it clinically available.