What is the most likely identification for a patient with a severe eye irritation caused by a gram-negative rod that tests positive for cytochrome oxidase?

The most likely identification for a patient with severe eye irritation caused by a gram-negative rod that tests positive for cytochrome oxidase is Pseudomonas aeruginosa. This organism is well known for causing a variety of infections, particularly in immunocompromised individuals and in settings where there is exposure to contaminated water or surfaces, which aligns with the symptoms of severe eye irritation.

Pseudomonas aeruginosa is characteristically a strict aerobic rod that not only tests positive for cytochrome oxidase but is also notorious for its resilience, antibiotic resistance, and ability to thrive in various environments, including hospital settings. The positive oxidase test is a key differentiating characteristic for this organism, as it indicates the presence of cytochrome c oxidases, which play an essential role in cellular respiration.

This bacterium is commonly associated with conditions such as keratitis, especially in contact lens wearers or individuals with trauma to the eye, which further supports the likelihood of Pseudomonas aeruginosa being the causative agent in this case of severe eye irritation.