Spider Venom-Derived Peptide Eye Drops Effectively Treat Resistant Bacterial Eye Infections in Rabbits

Eye drops containing LyeTxI-b — a synthetic antimicrobial peptide designed from a Brazilian wolf spider (Lycosa erithrognatha) venom toxin — effectively treated resistant bacterial keratitis in rabbits with no signs of ocular toxicity. The peptide killed planktonic Staphylococcus aureus bacteria at a very low concentration (MIC 3.6 μmol/L), reduced biofilm viability by 90%, and when applied as drops four times daily for one week, eliminated bacteria and reduced inflammatory cell activity to levels comparable to healthy untreated eyes. Toxicity testing on chorioallantoic membranes and the standard Draize eye irritation test showed no adverse effects.

Researchers induced bacterial keratitis in New Zealand white rabbits by intrastromal injection of S. aureus (4 × 10⁵ cells). The peptide eye drop formulation (LyeTxI-b 28.9 μmol/L in 0.5% CMC and 0.9% NaCl) was instilled four times daily for one week. Outcomes included slit-lamp biomicroscopy, corneal histopathology, and quantification of inflammatory cell infiltration through myeloperoxidase (MPO) and N-acetylglucosaminidase (NAG) assays. Ocular safety was assessed via chorioallantoic membrane and Draize tests. In vitro MIC and biofilm viability assays were also performed.

Bacterial keratitis (corneal infection) can cause rapid, severe vision loss and is a leading cause of corneal blindness worldwide. Antibiotic-resistant strains of Staphylococcus aureus are increasingly common, and bacteria protected within biofilms on the corneal surface are notoriously difficult to treat. Spider venom-derived peptides offer a fundamentally different antimicrobial mechanism than conventional antibiotics — they typically disrupt bacterial membranes, making resistance development much harder. The added anti-inflammatory activity of LyeTxI-b addresses both the infection and the damaging immune response.

Antibiotic resistance is a growing crisis in ophthalmology, with resistant corneal infections increasingly difficult to treat. Antimicrobial peptides derived from venoms represent one of nature's oldest defense systems against infection and offer mechanisms of action that bacteria struggle to develop resistance against. The fact that LyeTxI-b also reduces inflammation is a significant bonus — most antibiotics treat the infection but do nothing for the inflammatory damage that often causes the actual vision loss. Spider venom peptides join a growing pipeline of venom-derived therapeutics in ophthalmology.

This is a rabbit model — ocular pharmacokinetics and immune responses differ between rabbits and humans. The study tested only S. aureus, so efficacy against other keratitis pathogens (Pseudomonas, fungi) is unknown. Sample sizes for the animal experiments are not specified in the abstract. The one-week treatment duration doesn't address whether longer courses would be needed for more severe infections. Manufacturing, stability, and cost considerations for a clinical formulation are not discussed.