The new lamellar techniques for selective replacement of diseased layers of the cornea, which are now largely preferred over penetrating keratoplasty, have been related, at least to some extent, to an increased trend of post keratoplasty fungal infection in the USA. Two factors have been suggested as risk factors: first, these techniques might enhance infiltration of infectious organisms in the lamellar interspace and second, but no less importantly, the cold storage media commonly used in the US do not contain antimycotic agents.
Recently, our R&D team has concluded the studies to assess the in vitro killing efficacy of Kerasave against various Candida species commonly associated with keratitis and endophthalmitis, including C. albicans, C. glabrata, and C. tropicalis.
Kerasave, a new storage medium developed by Alchimia Srl (Italy), which is supplied with an Amphotericin B tablet to be added to the medium before use (thus giving a final concentration 2.5 µg/ml), is intended for the storage of donor corneas at 4°C for up to 14 days.
Kerasave showed high antifungal efficacy against susceptible fungal strains at 4°C, in particular against C. albicans and C. tropicalis. Already within 5 days of incubation, four of the six strains contaminated with 10 CFU/ml demonstrated a significant ≥ 3 Log10 reduction on average as compared to controls (p < 0.01).
The usefulness of adding an antimycotic agent to cold storage media is still a matter of debate in the USA, mainly because of some concerns about efficacy and safety issues. The results of this study help to dispel all these doubts, as:
- to obtain truly reliable results on the antimycotic efficacy, all liquid samples before plating were treated with RESEP (Alchimia srl), a syringe-like, patented, CE marked device, which contains a resin mixture for the removal of antimicrobials from samples to avoid false-negative results during the microbiology assay;
- the absence of cytotoxicity, irritation, or sensitization of Kerasave media were assessed by cytotoxicity, topical ocular irritation, and delayed hypersensitivity tests according to the ISO 10993-5 and 10993-10.
Besides, it should be reminded that transplanting the donor graft soon after tissue recovery (as commonly performed in the USA) does not leave the time for microbiological testing before surgery; in case of post kerapoplasty infection, the only option is the recipient treatment.
Therefore, the results of the time-kill studies add further data in favour of the antimycotic safety and efficacy and safety of supplementation of cold corneal storage media with Amphotericin B.