Abstract
Background:
Bacterial contamination of medical equipment is a significant risk in both human and veterinary medicine, leading to potential cross-contamination between clinicians, technicians, patients, and healthcare professionals. Pathogens can persist on surfaces, resulting in healthcare-associated infections. Tonometry used to measure intraocular pressure (IOP) for diagnosing conditions like glaucoma and uveitis, is crucial in both human and veterinary care. However, there is limited information on bacterial transmission through reused tonometer probes in veterinary patients. This pilot study aimed to explore the potential for cross-contamination of bacteria via a rebound tonometer probe using bacterial isolates linked to bacterial ulcerative keratitis in dogs.

Aim:
To evaluate the potential for bacterial transmission via rebound tonometry using the ICare® TONOVET Plus in a controlled laboratory environment. The study focused on two bacterial isolates commonly implicated in canine bacterial ulcerative keratitis: Pseudomonas aeruginosa and beta-haemolytic Streptococcus.

Methods:
Bacterial cultures were inoculated on blood agar and MacConkey agar plates. Tonometer probes were used to perform multiple corneal rebounds (CR) readings on known bacterial samples, followed by multiple CR readings on agar growth plates, incubation and re-examination of the agar plates for evidence of bacterial transfer. Controls included plates where the probes were only used on sterile agar.

Results:
Bacterial transmission was detected with distinct bacterial colonies corresponding to individual CR readings on the plates inoculated with Pseudomonas and beta-haemolytic Streptococcus. A control plate exhibited a single bacterial colony, likely due to inadvertent contamination.

Conclusion:
The results indicate that bacterial transmission via rebound tonometer probes is possible. Although this was an in vitro study, the findings raise concerns about cross-contamination in clinical practice. Changing tonometer probes between patients, particularly after those with bacterial ulcerative keratitis is advised until further investigation into the in vivo bacterial transmission is investigated.

Key words: Bacteria, Contamination, Culture, Tonometry