Cold atmospheric pressure plasma jet for the treatment of Aspergillus keratitis

Purpose

In an in-vitro and in-vivo study, we investigated the effect of cold atmospheric pressure plasma jet (CAPPJ) in the treatment of Aspergillus fumigatus (A. fumigatus) keratitis.

Methods

In the in vitro phase, suspensions of A. fumigatus with 10⁶ colony forming units (CFUs) were exposed to CAPPJ, 1, 2, 3, 4, and 5 min per day for 7 consecutive days. After culturing the post-treatment suspension in Saboraud dextrose agar, fungal colonies were counted. The same experiment was performed for fungal colonies cultivated on agar plates. Mean logarithm of CFUs were compared between the baseline and CAPPJ-treated groups and also between the exposure times by using Friedman and Bonferroni tests. In the in vivo phase, 3 rabbits with A. fumigatus keratitis were treated with CAPPJ, 5 min daily for 3 days followed by microbiologic and histopathologic investigations on the excised corneas.

Results

Agar plate and broth media treatment assays disclosed a significant decreasing rate in mean logarithm of CFUs with increased exposure time as compared to the baseline (P = 0.010 and P = 0.012, respectively). This decrease in both treatment assays was statistically significant in the 5 min-treatment group in comparison with the baseline (P = 0.016). However, in broth medium treatment assay, the decrease was slower and less than CAPPJ-treated agar plates. Direct application of the plasma jet in experimental model of rabbit A. fumigatus keratitis resulted in significant fungal inactivation evidenced by microbiologic and histopathologic investigations.

Conclusion

Both in vitro and in vivo results demonstrated that CAPPJ treatment was effective in inactivating fungal pathogens and therefore it may be considered as a new treatment modality for fungal keratitis. However, further studies are required to investigate its long-term safety.