Innovative Cold Atmospheric Plasma (iCAP): Efficacy for Bacterial Keratitis and Comparison to Antibiotics

Abstract

Purpose : Previously, application of innovative cold atmospheric plasma (iCAP) to infected rabbit corneas was efficacious for Pseudomonas aeruginosa (PA) keratitis. We aimed to compare iCAP to antibiotics and analyze its efficacy against Staphylococcus aureus.

Methods : New Zealand white rabbits were used to evaluate iCAP efficacy against methicillin-resistant S. aureus (MRSA) and PA keratitis. Groups were untreated (control), topical moxifloxacin (MOX), iCAP, and iCAP + MOX. Additional groups of topical vancomycin (VAN) and iCAP + VAN were included in the MRSA study (n ≥ 6 per group). Keratitis was induced in anesthetized rabbits by intrastromal injection of bacteria, followed by 3 iCAP and 4 antibiotic treatments until 24 hours. Clinical scores were assigned in a blinded fashion 25 hours after infection. Rabbits were euthanized and corneal bacterial loads were quantitated. Kruskal-Wallis test was used for initial data analysis followed by pairwise comparisons with Dunn’s test.

Results : For MRSA, treatment with iCAP resulted in lower clinical scores (9.813 ± 0.861) than control (14.219 ± 1.087) or MOX-treated (12.813 ± 1.956) eyes (p ≤ 0.020). VAN-treated eyes had lower scores (9.583 ± 1.076) than those of control or MOX (p ≤ 0.030). Parameters exhibiting improvement with iCAP were fibrin accumulation in the anterior chamber and presence/size of corneal ulceration. Eyes treated with iCAP, iCAP + MOX, and iCAP + VAN had lower colony-forming units (CFU) of MRSA than control or MOX-treated eyes (p ≤ 0.038); with loads of 4.826 ± 0.636, 4.277 ± 0.821, 5.341 ± 0.538, 7.098 ± 0.260, and 6.731 ± 0.500 log₁₀ CFU, respectively. For PA, treatment with iCAP + MOX resulted in reduced clinical scores (10.313 ± 0.978) compared to control (15.656 ± 1.397) or iCAP-treated (16.719 ± 1.618) eyes (p ≤ 0.029). Parameters exhibiting improvement with iCAP + MOX were fibrin accumulation in the anterior chamber, stromal infiltrate (haze), and presence/size of corneal ulceration. Eyes treated with MOX or iCAP + MOX had lower PA loads compared to control and iCAP-treated eyes (p ≤ 0.031); with loads of 2.123 ± 0.570, 1.159 ± 0.718, 7.518 ± 0.068, and 6.513 ± 0.44 log₁₀ CFU, respectively.

Conclusions : iCAP alone or in combination with antibiotics significantly reduces bacterial loads and improves clinical scores for MRSA and PA keratitis.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.