Evaluating novel therapeutic options of fatty acid compounds and essential oils to combat bacterial ocular infections

Bacteria pathogens cause ocular infections that may lead to visual impairment or blindness. Neisseria gonorrhoeae ocular infections predominate in new-borns as ophthalmia neonatorum while Staphylococcus aureus and Pseudomonas aeruginosa eye infections are common in adults. The rise in resistance strains and antibiotic treatment failures necessitates that novel therapeutic agents are developed.

This research aims to evaluate natural products and develop a candidate into ophthalmic formulations that can prevent and treat bacterial eye infections. A panel of 44 fatty acid compounds and six essential oils were screened. At ≤ 6.25 mM, caprylic acid, pelargonic acid, monocaprin and oregano oil (≤ 0.39%) were effective against N. gonorrhoeae NCCP 11945, S. aureus NCTC 6571 and P. aeruginosa ATCC 15442 and demonstrated broad spectrum activity against a range of Gram positive and Gram-negative bacteria. Caprylic acid was formulated into eyedrops (5% w/v) and contact lens solution (5% w/v) that were safe in ocular irritation and cytotoxicity assays. The caprylic based eyedrops were effective against N. gonorrhoeae, S. aureus and P. aeruginosa and caprylic contact lens solutions compared favourably with commercially available contact lens solutions in their disinfection properties. Furthermore, eight lipase treated non-volatile oils (rapeseed, sunflower, olive, groundnut, grapeseed, sesame, avocado and coconut oils) demonstrated anti-gonococcal properties. Additionally, an ex vivo bovine corneal infection and clearance model suitable for N. gonorrhoeae, S. aureus and P. aeruginosa was developed. Further testing in ex vivo and in vivo models can establish the therapeutic concentrations of the developed ophthalmic formulations prior to clinical use.