A novel ex vivo bovine corneal infection and clearance model for Neisseria gonorrhoeae, Staphylococcus aureus, and Pseudomonas aeruginosa.

Abstract

Ocular infections caused by bacterial pathogens may damage the cornea and rapidly progress to permanent blindness. Topical application of an ophthalmic formulation is often used to treat corneal infections. The animal models used in many preclinical studies frequently involve expensive in vivo experiments that compromises the corneal epithelium to mimic real life conditions such as during contact lens wear, but these do not consider other instances where infection occurs in intact corneas such as in ophthalmia neonatorum. To develop an ex vivo model of infection, bovine eyes from human food chain waste were processed and the corneas inoculated with Neisseria gonorrhoeae strain NCCP 11945, Staphylococcus aureus strain 6571, and Pseudomonas aeruginosa strain ATCC 15442 for 1 hour, 4 hours, and 6 hours, respectively. Inoculation included intact bovine corneas and those compromised with scalpel, needle, and blot methods. Recovery of N. gonorrhoeae, S. aureus, and P. aeruginosa colonies demonstrated that infection of bovine corneas was achieved with intact and compromised corneas using this model. In addition, corneas inoculated with the bacteria were treated with a suitable antibiotic, demonstrating clearance of the bacterial infections with at least 5 log10 reduction. This model is appropriate for both establishing infection and testing the ability of antimicrobial agents to clear bacterial eye infections. The bovine ex vivo model is reliable, cost-effective, suitable for different bacteria species, and reduces the need for further animal exploitation in laboratory research. Author SummaryBacterial pathogens such as Neisseria gonorrhoeae, Staphylococcus aureus, and Pseudomonas aeruginosa infect the eyes, damage the clear transparent cornea and may eventually cause blindness. Several in vivo animal models that have been used to investigate corneal infections in preclinical studies involve compromising the integrity of the corneal epithelium, which predisposes the eye to infection and simulates conditions of corneal abrasion suggested to be seen during contact lens wear. However, corneal infection in infants during ophthalmia neonatorum occurs with intact corneal epithelium and as such may not be explained by abrasion simulating models. Also, in vivo experiments are expensive, involve invasive corneal procedures despite efforts at ethical compliance, and may be time consuming. Reliable models that are quicker, cost effective, cause less (or no) discomfort to animals, and simulate a wide range of corneal infection scenarios need to be explored. Here, we demonstrate the use of a novel ex vivo bovine eye model to establish bacterial infection of the cornea, with and without compromising the corneal epithelium, and clearance of the infection with selected antimicrobial agents. The optimisation of the ex vivo bovine corneal infection model may serve as a bridge between in vitro and in vivo models of corneal infection.