Abstract
Antibiotic resistance of bacteria common to the ocular surface is an evolving problem. Thus, novel treatment options with new modes of action are required. We investigated the antibacterial activity and safety of three commercially available topical veterinary ophthalmic products (cationic steroid antibiotics, products A and B, and a neutral superoxidized water, product C) to determine their potential use as antimicrobial alternatives. The minimum inhibitory concentrations (MIC) of the three products were determined against 17 antibiotic resistant bacterial clinical isolates from the ocular surface. Using a standard cytotoxicity assay, the products at varying concentrations were evaluated with a corneal fibroblast cell line and a macrophage-like cell line to determine their potential toxic effect in vitro. The commercial ophthalmic solutions, ofloxacin 0.3%, tobramycin 0.3% and gentamicin 0.3% were used as positive controls for the MIC and tobramycin 0.3% was used as positive control for the cytotoxicity assays. For the MIC, Product C showed no inhibition of growth for any organisms, while Products A and B showed inhibition of growth similar to slightly less than the positive controls. For the cytotoxicity assays, Product C exhibited minimal toxicity while Products A and B exhibited toxicity similar to the controls. In conclusion, Product C had no antibacterial activity in these assays, while Products A and B had antibacterial profiles similar to slightly less than common topical ophthalmic antibiotics and cytotoxicity profiles similar to common topical ophthalmic antibiotics. To our knowledge, this is the first report on the antibacterial activity and safety of the cationic steroid antibiotics and superoxidized water.
Highlights
Multi-drug resistant organisms of the corneal and conjunctival surfaces are a growing concern in numerous veterinary species [1,2,3,4,5]
The cationic steroid antibiotics, Products A and B,; neutral superoxidized water, Product C; and ophthalmic antibiotic solutions, ofloxacin 0.3%, (Akorn Inc., Lake Forest, IL, USA), tobramycin 0.3% (Bausch & Lomb Inc., Tampa, FL, USA) and gentamicin 0.3% (Bausch & Lomb Inc., Tampa, FL, USA), were all purchased from commercial vendors
For the single Neisseria sp. isolate, the cationic steroid antibiotics (CSAs) were less effective than the commercial antibiotics while Product C showed no inhibition of growth
Summary
Multi-drug resistant organisms of the corneal and conjunctival surfaces are a growing concern in numerous veterinary species [1,2,3,4,5]. A study investigating the antimicrobial resistance of 49 isolates of Staphylococcus pseudintermedius from the eyes of dogs with and without ocular disease concluded that fluoroquinolone resistance was increasing. Eighteen of 49 isolates were mec-A positive, 16 of which were oxacillin resistant. Efficacy and safety of CSAs and SOWs were resistant to more than one fluoroquinolone [1]. In another study investigating the prevalence of MRSA-associated keratitis in dogs, 71 Staphylococcus strains were isolated. Twentyfour percent of those strains were methicillin resistant [2]. The increasing prevalence of multidrug resistant bacteria illustrates the need for antimicrobial agents targeting novel sites to circumvent resistance
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