Topical blood products modulate the effects of ophthalmic antibiotics against common bacterial pathogens in dogs with infectious keratitis.
Authors: Kubai Melissa A, Roy Mackenzie M, Stinman Chloe C, Kenne Danielle E, Allbaugh Rachel A, Sebbag Lionel
Journal: Frontiers in veterinary science
Summary
Bacterial keratitis demands rapid, effective treatment to prevent corneal scarring and blindness, yet practitioners frequently combine topical antibiotics with blood products to control protease-mediated corneal breakdown—a practice that risks compromising drug efficacy through albumin-protein binding. Kubai and colleagues conducted an in vitro study using serum and plasma from 10 dogs and 10 horses (with albumin levels nearly double in equine samples) to test 30 bacterial isolates from canine keratitis cases against 17 antibiotics on standard susceptibility plates, comparing antibiotic minimum inhibitory concentrations (MICs) in blood product-free controls against eight test conditions. Canine blood products caused significantly greater MIC shifts than equine products (median 2-fold versus 2-fold but with narrower range; p=0.004), with some antibiotics showing MIC increases up to 10.8-fold, though selected drug-pathogen combinations paradoxically demonstrated improved susceptibility. For clinical application, prioritise equine serum over canine products and plasma alternatives, and consider delaying blood product administration by at least 15 minutes after the final antibiotic instillation to allow sufficient tear film drug concentration before albumin-induced binding becomes problematic.
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Practical Takeaways
- •If using topical blood products for corneal protection during keratitis treatment, consider equine serum over canine products as it causes less interference with antibiotic efficacy
- •Administer blood products ≥15 minutes after the last antibiotic eyedrop to reduce albumin-antibiotic binding in the tear film and maximize antibiotic effectiveness
- •Monitor clinical response closely when combining topical antibiotics with blood products, as MIC changes may reduce drug efficacy despite appropriate in vitro susceptibility
Key Findings
- •Equine blood products showed lesser impact on antibiotic MICs (median 2-fold change) compared to canine blood products (median 2-fold change, p=0.004), with equine serum producing direct antimicrobial effects particularly against Staphylococcus pseudintermedius
- •Blood product albumin concentrations were significantly higher in equine samples (25.9-26.5 mg/mL) than canine samples (13.8-14.6 mg/mL)
- •MIC changes ranged from 0.25-fold to 10.8-fold depending on antibiotic-pathogen combination and blood product type, with canine products causing greater increases in MICs
- •Serum showed greater antimicrobial effects than plasma, and fresh vs. frozen blood products demonstrated similar albumin levels and effects