Antimycotic Efficacy and Safety of a New Cold Corneal Storage Medium by Time–Kill and Toxicity Studies

Investigating the Influence of Temperature and Supplementation Timing on Antifungal Efficacy in Storage Medium for Corneal Transplantation

INTRODUCTION

Although antifungal supplementation reduces the fungal load in the corneal storage medium, consensus is lacking on the influence of dosing and temperature. The study aims to evaluate the impact of eye bank warming protocol and timing of antifungal supplements on efficacy in Optisol-GS and tissue.

METHODS

Corneoscleral rims contaminated with Candida albicans (C. albicans) were incubated in Optisol-GS, either without antifungal agents or with the addition of amphotericin B or voriconazole at various concentrations (2 ×, 5 ×, 10 ×, and 20 × MIC), at different time points, and under various preservation temperatures (2-8 °C versus 2 h-room temperature exposure). Antifungal efficacy was evaluated by counting viable yeast colonies cultured from Optisol-GS samples. Tissue sterility was determined through direct tissue culture and histological examination of the contaminated rims after a 14-day incubation period.

RESULTS

Room temperature exposure did not increase colony growth at the same multiple MIC of antifungal agents. Although antifungal addition reduced C. albicans growth in a concentration-dependent manner, yeast growth was still observed in all Optisol-GS samples with a single supplementation after a 14-day incubation. Only groups with additional antifungal supplementation on either day 2 or day 6 showed a 99% or greater reduction of C. albicans growth in Optisol-GS samples and yielded negative results in direct tissue culture.

CONCLUSIONS

The eye bank warming protocol did not compromise antifungal efficacy. To sustain the required concentration and effectively reduce C. albicans growth in Optisol-GS and contaminated tissue, additional antifungal supplementation on either day 2 or day 6 was necessary during a 2-week preservation period.

Synergistic activity of clioquinol with voriconazole and amphotericin B against fungi of interest in eye infections

Keratoplasty represents a risk factor for fungal eye infections, despites the antibacterial actives in the corneal tissue preservation means, it does not contain active substances with antifungal action. Among the most commonly associated fungal agents are the species belonging to the genera Fusarium and Candida. These agents can trigger an infectious process characterized by swift progression associated with high rates of morbidity, causing irreversible damage. Polyene and azole antifungals are the main agents of ocular therapy, however, they demonstrate some limitations, such as their toxicity and fungal resistance. In this context, drug repositioning and the combination of antifungals may be an alternative. Hence, the goal of this study was to investigate the potential activity of clioquinol (CLQ), a derivative of 8-hydroxyquinoline with previously described antifungal activity, along with its triple and quadruple combinations with antifungal agents commonly used in ophthalmic fungal therapy, natamycin (NAT), voriconazole (VRC), and amphotericin B (AMB), against main fungal pathogens in eye infections. The MICs for CLQ ranged from 0.25 to 2.0 μg/mL, for NAT from 4.0 to 32.0 μg/mL, for AMB it ranged from 0.25 to 16.0 μg/mL and for VRC from 0.03125 to 512.0 µg/mL. Among the tested combinations, the VRC-AMB-CLQ combination stands out, which showed a synergistic effect for more than 50 % of the tested strains and did not present antagonistic results against any of them. Toxicity data were similar to those antifungals already used, even with lower potential toxicity. Therefore, both clioquinol and the triple combination VCR-AMB-CLQ exhibited promising profiles for use as active components in corneal tissue preservation medium.

Prospective In Vitro Comparison of Kerasave and Optisol-GS Corneal Storage Solutions

PURPOSE

The aim of this study was to compare the performance of Kerasave and Optisol-GS for hypothermic corneal storage for 14 days.

METHODS

This study was a prospective laboratory investigation. Mate corneas were recovered into Kerasave or Optisol-GS (27 pairs) and stored at 2°C to 8°C for 14 days. Corneas were evaluated by trained eye bank technicians, and study parameters were compared between the initial and final evaluations. Endothelial cell density (ECD), hexagonality (HEX), and coefficient of variation (CV) were evaluated by specular microscopy, and central corneal thickness (CCT) was examined by optical coherence tomography after 1, 3, 7, and 14 days of storage. Corneal transparency was scored using slit lamp examination at days 1 and 14.

RESULTS

Average ECD, HEX, and CV for the Kerasave (2653 ± 303 cells/mm 2 , 57 ± 4%, and 36 ± 3%) and Optisol-GS (2623 ± 306 cells/mm 2 , 57 ± 5%, and 36 ± 4%) groups were not significantly different at day 1. There was also no difference at any other study time points (all P > 0.05). ECD did not significantly change from day 1 to day 14 in either group ( P > 0.05), but a statistically significant change in HEX and CV was observed between day 1 and day 14 in both groups ( P < 0.01). Average CCT measured at day 1 for corneas stored in Kerasave was 622 ± 49 μm and those stored in Optisol-GS was 580 ± 35 μm ( P < 0.01). The difference in CCT measurements was not significantly different at day 14 (Kerasave: 674 ± 46 μm vs. Optisol-GS: 647 ± 58 μm, P > 0.05). Corneal transparency was not significantly different between the 2 groups at day 1 or day 14.

CONCLUSIONS

The corneal quality and clinically relevant parameters including ECD, endothelial morphometry, and corneal transparency were not different in corneas stored in Kerasave or Optisol-GS for 14 days. The initial difference in CCT between the 2 groups decreased at day 14. These results demonstrated that Kerasave corneal storage solution preserves the corneal endothelium similarly to Optisol-GS.

Donor related corneal graft infection: a review of literature and preventive strategies

PURPOSE

Donor-related infections are a serious threat to patient safety after corneal transplantation. We provide a concise review of literature from the last decade on donor-related graft infections, sources of contamination and means to reduce the contamination of donor tissue and preservation media.

METHODS

We reviewed 50 papers from year 2005 to 2021 related to donor-related graft infections. We included 14 studies related to the risk factors associated with post-keratoplasty infection and preventive methods.

RESULTS

Incidence of post-keratoplasty infections has been reported to be approximately 0.2%-0.77% for endophthalmitis and 6.5%-10.5% for microbial keratitis. We analyzed six important studies regarding the risk factors related to donor contamination. It was observed that younger donor age, increased death to retrieval time, warming cycles and increased eye bank processing time and positive corneo-scleral rim cultures were important risk factors for donor-related infections post keratoplasty. Eye banks have adapted newer protocols over the time period for prevention of donor-related contamination. Recommended preventive strategies were published in about eight important studies over the past decade. In addition to meticulous donor screening, rapid warming cycles, double contact with povidone iodine during retrieval and addition of antifungals like amphotericin B, Voriconazole and cycloheximide have been suggested over the last decade although their use is still in debate with regard to the efficacy, toxicity and cost-effectiveness.

CONCLUSION

The last decade has witnessed a relative rise of fungal infections and multidrug resistant bacterial infections post-keratoplasty. Eye bank prepared corneas for lamellar surgeries are at increased risk for donor contamination due to increased exposure to the higher temperatures during their processing. Addition of antifungals and broad spectrum antibiotics to the hypothermic preservation media needs to be considered in the new era of increasing trends of lamellar keratoplasty.

Overview of Short-Term and Intermediate-Term Corneal Storage Solution: Comparison of Clinical Outcomes and Need For Future Research

ABSTRACT

Corneal donor tissue preservation techniques have incrementally improved since the introduction of McCarey-Kaufman storage solution from short-term storage to intermediate duration of storage with the advent of organ culture and Optisol GS storage solutions. Improved understanding of the corneal endothelial cell physiology has helped in designing newer storage solutions, such as the Life 4C and Cornea Cold. The incorporation of antibiotics, ATP precursors, minerals, and vitamins has improved the viability of tissues. In addition, these modifications to the newer storage solutions have increased the endothelial longevity and metabolic activity. Despite these advances, the duration of tissue storage has largely been restricted to 2 weeks in Optisol GS and 4 weeks in organ culture. The role and cost-effectiveness of antifungal supplementation and the need for improved epithelial preservation are additional areas that need to be explored. This review intends to summarize the efficacy and viability of donor corneas in different tissue storage solution and compare clinical outcomes while providing an insight into the challenges in developing newer methods of corneal preservation.

Endophthalmitis secondary to donor to host infection in posterior lamellar keratoplasties: A systematic review

Donor to host transmission of infectious agents is a well-recognized entity, more commonly related to Endothelial Keratoplasty (EK) than to Penetrating Keratoplasty (PK), that involves complications ranging from interface keratitis to endophthalmitis. A systematic review of the literature was conducted to identify the published articles until December 2020 reporting cases of endophthalmitis secondary to corneal graft contamination in posterior lamellar keratoplasties (DSAEK and DMEK) along with donor characteristics, microbiological profile, treatment and outcomes. Each identified article was assessed to meet donor to host infection criteria, defined as a post-procedural infection in which the same microbiological agent was identified in both the donor corneoscleral rim or preservation medium and receptor ocular tissue. From 23 research articles, eight reports of endophthalmitis in nine patients following DSAEK or DMEK secondary to donor to host infection fulfilled the inclusion criteria. The majority were male and the median age was 72.0 (45.0-81.0) years old. Indications of surgery were primarily pseudophakic bullous keratopathy and Fuchs dystrophy. A fungal pathogen was identified in eight of nine patients. All the cases underwent surgical management with lenticule removal or endothelial plaque aspiration. The final corrected distance visual acuity (CDVA) in all cases was 20/200 or better. Endophthalmitis after an EK procedure is a rare complication whose outcome depends on the aggressive and precocious treatment. Identification of early signs of interface keratitis and lenticule removal seems mandatory in patients undergoing DSAEK or DMEK to prevent further involvement of the globe.

Killing efficacy of a new hypothermic corneal storage medium against the micro-organisms frequently found in human donor cornea intended for transplantation

Objective

To study the in vitro killing efficacy of Kerasave (AL.CHI.MI.A Srl), a medium provided with amphotericin B tablet for hypothermic storage of human donor corneas, against relevant contaminants associated with postkeratoplasty infections.

Methods and Analysis

The antimicrobial activity of Kerasave was determined after 0, 3 and 14 days of incubation at 2°C-8°C, inoculating Kerasave and the control medium with 10⁵-10⁶ colony forming units (CFU) of Candida albicans (CA), Fusarium solani (FS), Aspergillus brasiliensis (AB), Staphylococcus aureus (SA), Enterococcus faecalis (EF), Bacillus subtilis spizizenii (BS), Pseudomonas aeruginosa (PA), Enterobacter cloacae (EC) and Klebsiella pneumoniae (KP). Log₁₀ reductions at different time intervals were determined by assessing the number of viable CFU using the serial dilution plating technique.

Results

After 3 days, Kerasave induced the highest log₁₀ decrease in the concentrations of KP, PA, CA and EC (5.37, 4.15, 2.97 and 2.67, respectively; all p<0.001). The log₁₀ decreases of SA and EF were 2.27 and 2.11, respectively (all p<0.001). The lowest log₁₀ decrease was observed in BS, AB and FS concentrations (0.25, 0.30 and 0.67, respectively; p<0.001 for BS and AB and p=0.004 for FS). After 14 days, the microbial count of CA, FS, SA, EF, PA and EC further decreased (p=0.006 for FS; p<0.001 for the others).

Conclusion

Kerasave effectively reduced or kept unchanged the microbial concentration of almost all tested strains after 3 days. Thus, this novel medium represents a valuable tool to control the microbial contamination of human donor corneas during hypothermic storage for up to 14 days before transplantation.

Pancreas preservation with amphotericin B deteriorates islet yield for porcine islet isolation

BACKGROUND

Amphotericin B is a crucial agent in the management of serious systemic fungal infections. It is also known to be cytotoxic. In this study, we evaluated the effect of amphotericin B added to the preservation solution on islet yield during islet isolation.

METHODS

Porcine pancreata were preserved in the preservation solution with or without amphotericin B (0.25 μg/mL) for approximately 18 hours at 4°C, and then islet isolation was performed. An optimized number (1750 IE) of isolated islets from each group were transplanted into streptozotocin-induced diabetic mice. The culture of isolated islets and acinar tissue with amphotericin B was also evaluated.

RESULTS

The islet yield before and after purification in the amphotericin B (-) group was significantly higher than that in the amphotericin B (+) group. After islet transplantation into diabetic mice, blood glucose levels reached the normoglycemic range, with 50% and 0% of that of the diabetic mice in the amphotericin B (-) and amphotericin B (+) groups, respectively. In the culture study, amphotericin B was found to be cytotoxic to porcine islets and acinar tissue.

CONCLUSIONS

Amphotericin B added to the preservation solution deteriorates islet yield during porcine islet isolation. Thus, the use of amphotericin B should be considered carefully for the preservation of the pancreas for islet isolation and islet culture before islet transplantation.

A new storage medium containing amphotericin B versus Optisol-GS for preservation of human donor corneas

BACKGROUND/AIM

We compared the quality of human donor corneas stored in a cold storage medium containing 2.5 μg/ml of amphotericin B (Kerasave, AL.CHI.MI.A. S.R.L., Ponte San Nicolò, Italy) and Optisol-GS (Bausch & Lomb Inc., Bridgewater, NJ, USA) for 14 days.

METHODS

Sixteen pairs of human donor corneas were collected in Eusol-C (AL.CHI.MI.A. S.R.L., Ponte San Nicolò, Italy). Next, all tissues underwent the first evaluation that included the assessments of central corneal thickness (CCT), endothelial cell density (ECD) measured using both trypan blue staining and specular microscopy, endothelial cell (EC) mortality and morphology, and corneal transparency within 24 hours from recovery (Day 1). Afterwards, one cornea of each pair was transferred into Kerasave or Optisol-GS. ECD and CCT were also assessed at Day 7, and all the metrics were evaluated again at the end of the storage period (Day 14).

RESULTS

At all tested time points, no differences were found in the qualitative (corneal transparency, EC morphology) and quantitative metrics (ECD, CCT, EC mortality) between the Kerasave and the Optisol-GS storage groups. At Day 14, the corneas stored in Kerasave and Optisol-GS showed ECD of 2312±98 and 2335±128 cells/mm² (p=0.886), CCT of 717±17 and 697±19 μm (p=0.454) and central EC mortality of 0.54%±0.40% and 0.14%±0.14% (p=0.719), respectively.

CONCLUSIONS

The new amphotericin B-containing medium Kerasave was comparable to Optisol-GS in terms of preservation of corneal characteristics at 2-8°C for 14 days.

Performance of New Hypothermic Corneal Storage Media With an Antimycotic Tablet in Comparison to Traditional Hypothermic Media During Simulated Eye Bank Processing

PURPOSE

To compare the performance of Kerasave (AL.CHI.MI.A. S.R.L., Ponte San Nicolò, Italy) containing 2.5 μg/mL of amphotericin B and Optisol-GS (Bausch & Lomb, Bridgewater, NJ) cold corneal storage media on donor corneas during routine eye bank procedures.

METHODS

Forty-four paired donor corneas were preserved after swab sample collection and povidone-iodine decontamination. Right and left corneas were immersed in Kerasave and Optisol-GS, respectively, and stored at 4°C before the initial evaluation. Paired corneas were assigned to processing subgroups for penetrating keratoplasty (n = 20), Descemet stripping automated endothelial keratoplasty (n = 14), or Descemet membrane endothelial keratoplasty (n = 10). Endothelial cell density, central corneal thickness, slit-lamp examination, and endothelial cell damage were assessed at different intervals. Sterility testing was performed on media samples.

RESULTS

At the initial evaluation, after 25.6 ± 3.2 hours of storage, the mean central corneal thickness of all corneas in Kerasave (n = 22) was greater than those in Optisol-GS (n = 22) (571 ± 12 μm vs. 526 ± 10 μm, respectively; P = 0.006). All other metrics were comparable between Kerasave and Optisol-GS in processing subgroups at all time intervals. Corneal swabs were positive in 90% of corneas before decontamination with povidone-iodine. At the initial evaluation, fungal contamination was detected in 24% and 19% of Kerasave and Optisol-GS, respectively. At the final evaluation, no fungi was detected in Kerasave and 1 Optisol-GS sample was positive (P = 0.999).

CONCLUSIONS

Metrics of corneas stored in Kerasave and Optisol-GS were comparable. Kerasave might be considered an antifungal-possessing alternative to Optisol-GS.

Fungal infection after keratoplasty and the role of antifungal supplementation to storage solution: a review

Fungal infection after corneal transplantation is a rare, yet potentially devastating, postoperative complication and has become a growing concern for the transplant surgeon and eye banking community. The Eye Bank Association of America (EBAA) has reported an increasing trend in the rate of postkeratoplasty fungal infections and a reversal in the previously documented predominance of bacterial over fungal infections. Additionally, several studies have confirmed a high correlation between positive corneoscleral donor rim fungal cultures and postoperative infections. Optisol GS (Bausch & Lomb, Irvine, California, USA), the most extensively used corneal storage solution in US eye banks, does not currently contain any antifungal supplementation. Although large randomised control trials evaluating the efficacy and safety of routine antifungal supplementation to corneal storage solution are lacking, several investigative studies have assessed the role of antifungal agents in reducing fungal contamination of donor corneas without causing undue corneal toxicity. This review will present the current epidemiology of postkeratoplasty fungal infections and evidence for obtaining routine fungal rim cultures and antifungal supplementation of storage solution.