Sight-threatening antibiotic-resistant eye infections are becoming a significant threat to vision in dogs, cats, and horses, according to a newly published comprehensive review. The study examines global trends in antimicrobial resistance in animal eye infections and warns that multidrug-resistant bacteria are becoming more common in referral veterinary settings. The review also highlights a critical challenge for veterinarians: standard laboratory tests may not always predict how well topical eye treatments will work in practice. The authors call for earlier diagnostic testing, more targeted antibiotic use, stronger infection-control measures, and the development of antibiotic-sparing strategies to help preserve treatment options for future patients.

Sight-threatening eye infections in pets and horses are becoming more difficult to treat as antibiotic-resistant bacteria spread worldwide, according to a new review published in Veterinary Ophthalmology by researchers from the Hebrew University of Jerusalem.

The review by Dr. Lionel Sebbag and Dr. Oren Pe'er of the Koret School of Veterinary Medicine, Hebrew University of Jerusalem, examines the growing challenge of antimicrobial resistance (AMR) in veterinary ophthalmology, with a particular focus on bacterial corneal infections that can threaten vision within hours or days if left uncontrolled.

Bacterial keratitis, a serious infection of the cornea, is among the most urgent emergencies in veterinary eye care. While antibiotics remain the cornerstone of treatment, the researchers found mounting evidence that many of the bacteria responsible for these infections are becoming increasingly resistant to commonly used drugs.

Drawing on studies from North America, Europe, Asia, South America, and Australia, the review identifies Staphylococcus pseudintermedius, beta-hemolytic streptococci, and Pseudomonas aeruginosa as the most frequently isolated bacterial pathogens in companion animals. Particularly concerning is the rising prevalence of multidrug-resistant strains, especially in referral and specialty-care settings where the most severe cases are concentrated.
One of the most consistent findings across studies was the impact of previous antibiotic use. Animals that had recently received topical antimicrobial treatment were more likely to harbor resistant bacteria and less likely to yield positive culture results, making accurate diagnosis and targeted treatment more challenging.

The review also highlights a surprising gap between laboratory testing and real-world clinical outcomes. Standard antimicrobial susceptibility tests are largely based on how antibiotics behave when administered systemically, yet eye drops achieve very different drug concentrations at the ocular surface. As a result, laboratory susceptibility reports may not always accurately predict whether a treatment will succeed or fail in clinical practice.

“Antimicrobial resistance is no longer a theoretical concern in veterinary ophthalmology,” the authors note. “It is a clinically significant and evolving reality.”

The researchers argue that laboratory findings should always be interpreted alongside clinical observations, disease severity, and patient history. They emphasize the importance of obtaining microbiological samples before extensive antibiotic treatment whenever possible, allowing veterinarians to make more informed treatment decisions.

Beyond the immediate clinical implications, the review places antibiotic-resistant eye infections within a broader One Health framework. Some bacterial species commonly found in animal eye infections have recognized zoonotic potential, meaning they can be transmitted between animals and humans.
The authors note that veterinary clinics, equipment, and even households can serve as environments where resistant organisms circulate, highlighting the importance of rigorous hygiene and infection-control practices.

Looking ahead, the review explores a range of antibiotic-sparing approaches designed to reduce reliance on traditional antimicrobials. These include antiseptic therapies, biofilm-disrupting treatments, corneal cross-linking technologies, ultraviolet-based approaches, and other emerging methods that may complement conventional antibiotic therapy.

The authors conclude that preserving the effectiveness of existing antibiotics will require coordinated efforts in surveillance, antimicrobial stewardship, infection control, and the development of ophthalmology-specific guidelines for managing ocular infections.

“The goal is not simply to resolve the current infection,” the authors write, “but to preserve therapeutic reliability for future patients.”