Evaulation of predatory bacteria on corneal wound healing, ocular safety, and clearance of fluoroquinolone resistant Pseudomonas aeruginosa from the ocular surface

Abstract

Purpose : The increasing spread of antibiotic resistant microorganism is a global health problem. Generation of novel approaches to deal with antibiotic resistant pathogens is essential. Predatory bacteria are bactericidal to ocular pathogens in vitro. The goal of this study was to test the safety of predatory bacteria on the ocular surface, and to determine whether they can kill multi-drug resistant P. aeruginosa on the ocular surface.

Methods : Predatory bacteria, Bdellovibrio bacteriovorus strains 109J and HD100, and Micavibrio aeruginovous (10⁷ PFU), were applied to the ocular surface of NZW rabbits five times a day for five days. Controls included saline (negative control) or vancomycin (50 mg/ml as a positive control for toxicity). The rabbit eyes (n=9 per group) were either left intact or had the corneal epithelium removed with an Amoil’s epithelial scrubber. Eyes were stained with fluorescein and evaluated with a slit lamp and a modified MacDonald-Shadduck scoring system of ocular toxicity. Wound sizes were measured. The experiment was carried out for 12 days and eyes were evaluated on days 1-5, 8, 10, and 12. To evaluate bacterial clearance from the ocular surface P. aeruginosa strain PaC was applied to the ocular surface of intact rabbit eyes (10⁹ CFU/eye, n=12 eyes) followed by three applications of predatory bacteria (~10⁸ PFU/eye) at hour 1, 3, and 5 post-PaC inoculation. At 0.5, 2, 4, and 6 hours the ocular surface was swabbed and PaC were enumerated.

Results : Predatory bacteria were non-toxic to the ocular surface and did not alter wound healing, whereas significant toxicity and a remarkable inhibition of wound healing was observed in the vancomycin treated eyes (p<0.05). Fluoroquinolone-resistant P. aeruginosa was more rapidly cleared from the ocular surface in predatory bacteria treated eyes, most notably those treated with M. aeruginovous.

Conclusions : Predatory bacteria are non-toxic to the rabbit ocular surface and may be developed as a new method for the treatment of antibiotic resistant ocular pathogens.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.