Combination antibiotic supplementation of corneal storage medium

Assessment of performance and safety of Corneal Chamber hypothermic storage medium and PSS-L corneal rinsing solution in human and porcine corneas

PURPOSE

To prove the safety and performance of the hypothermic corneal storage medium "Corneal Chamber" and the rinsing solution "PSS-L" in support of the new Conformité Européenne (CE) certification process in accordance with the Medical Device Regulation.

METHODS

Fifteen (n=15) human donor corneas and 11 (n=11) porcine corneas were evaluated for the following parameters: endothelial cell density (ECD) and mortality, percentage of hexagonal cells (HEX%), coefficient of cellular area variation (CV%) and corneal transparency at Day 0 and after 14±1 days of storage in Corneal Chamber medium at 2-8°C. Then, the same parameters were assessed after rinsing of corneas in PSS-L for 1 min at room temperature. Evaluation of gentamicin sulfate carryover after corneal storage and PSS-L rinsing was performed by ultra-high performance liquid chromatography analysis on human corneas homogenates.

RESULTS

Human and porcine corneas stored in Corneal Chamber medium showed a good overall quality of the tissue according to the quality parameters evaluated. In particular, mean ECD, HEX% and CV% did not show statistically significant changes at the end of storage and endothelial mortality increased to 3.1±3.3 and 7.8±3.5% in human and porcine corneas, respectively. Tissue rinsing with PSS-L did not affect the quality parameters evaluated before and gentamicin sulfate residues were absent in human corneas.

CONCLUSIONS

Corneal preservation in Corneal Chamber medium at 2-8°C for 14 days and the corneal rinse with PSS-L are safe and effective procedures allowing the preservation of the corneal quality parameters as well as the complete elimination of gentamicin sulfate from the tissues before transplantation.Cite Now.

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.

Cold Storage Media versus Optisol-GS in the Preservation of Corneal Quality for Keratoplasty: A Systematic Review

Optisol-GS is the most widely used pharmaceutical composition to preserve corneas for transplantation. This systematic review investigated the effects of different cold corneal storage media (CCSM) compared with Optisol-GS on the quality of stored corneas. The literature was searched throughout May 2022 on six databases and grey literature. Studies including corneas (population) exposed to distinct cold storage media (exposure) and Optisol-GS (comparison) that reported qualitative and/or quantitative parameters of cornea quality (outcome) were included. Methodological quality was assessed using ToxRTool. From 4520 identified studies, fourteen were included according to the eligibility criteria, comprising 769 evaluated cornea samples comparing Optisol-GS with commercial and noncommercial media. All studies showed good methodological quality. Experimental times ranged from 1–28 days, mainly using 4 °C as the preservation temperature. Viable endothelial cell density (ECD) and endothelial cell morphology (EC) were the most assessed parameters. ECD results for Cornisol were higher than Optisol-GS in 10 days (p = 0.049) and favored Cornea ColdTM up to 4 weeks (p < 0.05), which also showed better qualitative results. While the standardization of test protocols could improve comparisons, evidence indicates that most CCSM present similar performances on cornea preservation for transplantation at seven days, while some formulations may increase preservation at extended times.

Fungal infection after endothelial keratoplasty: association with hypothermic corneal storage

PURPOSE

To compare the incidence of fungal infection after endothelial keratoplasty (EK) when donor tissue had been stored in hypothermic medium or organ culture.

METHODS

We describe the clinical features of 10 cases of fungal infection (keratitis or endophthalmitis) following EK identified at three European centres. Case definition was the culture of fungus or a positive PCR from the host cornea or anterior chamber after EK. A survey of the incidence of infection after EK was conducted by the European Eye Bank Association. The main outcome measure was the number of cases in which donor tissue had been stored in hypothermic medium compared with organ culture.

RESULTS

The 10 cases occurred between 2014 and 2017. All donor corneas had been stored in hypothermic medium sourced from three US eye banks. Three pairs of mate corneas caused infections in six recipients. Candida spp were identified from nine cases, with one isolate of Purpureocillium lilacinum. Data on 16 862 corneas supplied for EK were available from 16 European eye banks for the 5-year period from 2012. There were 17 reported cases of infection, of which 15 (88%) were fungal infections and 14 (82%) were Candida spp. Fungal infection was reported from 3 of 14 476 (0.02%) corneas supplied in organ culture compared with 12 of 2386 (0.50%) corneas supplied in hypothermic medium (p<0.0001). The incidence of infection after hypothermic storage was similar for material sourced from Europe (0.52%) or the USA (0.61%).

CONCLUSIONS

Infection after EK is strongly associated with Candida spp. The possible explanations for the higher incidence of infection when tissue is stored in hypothermic medium are discussed.

Serologic Evaluation of Cornea Donors and Microbiologic Evaluation of Cornea Storage Media in an Eye Bank from Izmir, Turkey

OBJECTIVES

Our objective was to evaluate the serologic positivity of cornea donors and microbiologic positivity of cornea storage media at the Ege University Tissue and Cornea Bank, Izmir, Turkey.

MATERIALS AND METHODS

We retrospectively investigated the serologic blood sample and microbiological culture media analysis results of all cornea donors at Ege University Tissue and Cornea Bank between 2007 and 2015 with reference to age, sex, and cause of death of each donor.

RESULTS

Mean age of the 955 deceased donors was 43.19 ± 15.89 years (range, 2-65 y). The mean postmortem time to blood sample removal and excision of the cornea tissue was 8.4 hours (range, 4-12 h). Serologic analyses showed that 855 donors (89.5%) were seronegative. The remaining donors were seropositive for hepatitis B (54 donors; 5.7%), human immunodeficiency (27 donors; 2.8%), hepatitis C (14 donors; 1.5%), and syphilis (5 donors; 0.5%) virus infections. Microbiologic analyses of the storage media were negative, with no microorganisms shown in 855 samples (89.5%). Candida species (32 donors; 3.4%), Escherichia coli (14 donors; 1.5%), Pseudomonas aeruginosa (11 donors; 1.2%), methicillin-resistant Staphylococcus aureus (11 donors; 1.2%), Enterobacter species (11 donors; 1.2%), Klebsiella pneumoniae (7 donors; 0.7%), Acinetobacter baumannii (6 donors; 0.6%), Proteus species (5 donors; 0.5%), and Corynebacterium species (3 donors; 0.3%) were the detected microorganisms in the infected storage media.

CONCLUSIONS

False-positive serologic results among cornea donors were high. The incidence of false-positive results might be decreased by earlier blood removal from deceased donors and testing of all potential donors in intensive care units. Although rare, endophthalmitis after keratoplasty might be a devastating problem. In addition to serologic testing, microbiologic analyses of cornea storage media before transplant may be an effective way to prevent postoperative infectious complications.

In Vitro Antimicrobial Long-Term Evaluation of Corneal Preservation Media Against Microorganisms Using A Closed-Chamber Study Model

PURPOSE

To evaluate the existence of in vitro long-term antimicrobial activity of Optisol-GS against microorganisms related to corneal infection using a closed-chamber study model.

METHODS

Optisol-GS was contaminated with microorganisms related to corneal infections, and different times after contamination was analyzed using a closed-chamber study model. Microbial growths were analyzed by macroscopic observation.

RESULTS

For Staphylococcus aureus and Pseudomonas aeruginosa, bacterial growth was observed in samples taken 1 hour through 7 days and 14 days after contamination occurred. For Staphylococcus epidermidis, Streptococcus agalactiae, and Candida albicans, microbial growth was observed in all samples studied. For Streptococcus pneumoniae, bacterial growth was observed in samples taken 1 hour through 72 hours after contamination. For Streptococcus pyogenes, bacterial growth was observed in samples taken 1 hour through 7 days after contamination. For Escherichia coli, bacterial growth was observed in samples taken 1 hour through 48 hours after contamination occurred.

CONCLUSIONS

We conclude that no in vitro antimicrobial effect for any microorganism analyzed was observed in contaminated Optisol-GS after 72 hours; however, effective antimicrobial activity was observed for S. aureus, Str. pneumoniae, Str. pyogenes, P. aeruginosa, and E. coli after 7 to 10 days.

The safety and efficacy of linezolid and daptomycin as an additive in Optisol-GS against methicillin-resistant Staphylococcus aureus

PURPOSE

To evaluate the efficacy of adding either linezolid or daptomycin to Optisol-GS donor storage medium in reducing methicillin-resistant Staphylococcus aureus (MRSA) contamination of donor corneas.

METHODS

Optisol-GS was supplemented with either linezolid at 2×, 4×, or 10× minimum inhibitory concentration (MIC) or daptomycin and calcium at 5× or 50× MIC. Unsupplemented control groups were also used. Gentamicin-sensitive and gentamicin-resistant isolates of MRSA were added, and vials were refrigerated for 48 hours followed by sampling for viable colony counts immediately upon removal from refrigeration and after warming to room temperature for 3 hours. Safety studies of Optisol-GS supplemented with 50× MIC daptomycin and calcium were performed by evaluating the central corneal thickness and endothelial cell density of the donor cornea. Stability of daptomycin in Optisol-GS at storage was also tested.

RESULTS

No added benefit was observed with linezolid supplementation to Optisol-GS against gentamicin-sensitive MRSA, with reduction in viable colony counts by >90% in all groups. No benefit was observed with linezolid supplementation against gentamicin-resistant MRSA, with the majority of inocula remaining viable in all groups. Viable counts of gentamicin-sensitive MRSA and gentamicin-resistant MRSA were effectively reduced with both 5× MIC and 50× MIC daptomycin supplementation. 50× MIC daptomycin-supplemented Optisol-GS had no appreciable effect on the central corneal thickness or endothelial cell density of the donor cornea and was stable at storage for 14 days.

CONCLUSIONS

The addition of daptomycin to Optisol-GS significantly increases the anti-MRSA activity of the medium without any apparent negative effects on donor corneal tissue.

Preserving the cornea: corneal storage media

PURPOSE OF REVIEW

The aim of this article is to review the recent literature regarding corneal storage media since the last review that discussed this topic in substantial detail in this journal.

RECENT FINDINGS

During the last few years, despite the development of new corneal storage media and the addition of new additives to established corneal storage media, Optisol GS (Bausch & Lomb, Irvine, California, USA) has continued to remain the popular choice among storage media used in the United States, and traditional organ culture methods are still used in Europe. Recognizing that persistent epithelial defects after corneal transplantation can be a serious complication, however, attention has started to focus on not only preserving the endothelium, but also the epithelium. In addition, there has been more research towards antimicrobial prophylaxis.

SUMMARY

With recent evidence suggesting that longer storage times may allow better outcomes in high-risk grafts because of the depletion of donor T cells from the donor cornea into the storage media, storage media will need to be optimized for preserving the endothelium for longer periods of time. In addition, because the epithelium is typically unable to be sustained for longer than 1 week in storage media, research toward preserving the epithelium will also be essential.

Deep anterior lamellar keratoplasty for keratoconus

PURPOSE

To investigate surgical outcomes after deep anterior lamellar keratoplasty (DALKP) in eyes with keratoconus.

METHODS

Retrospective review of 127 eyes of 118 keratoconus patients who underwent DALKP at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia between January 1, 1998 and November 30, 2001. The mean age of all patients was 25.9 years (range 11-70 years). The mean follow-up for all patients was 10.9 months (range 4-61 months). Baring of Descemet's membrane (DM) during DALKP was achieved in 47 (37%) eyes; some stroma was left during operation in the remaining 80 (63%) eyes. Snellen visual acuity, intraoperative complications, and postoperative graft status were assessed.

RESULTS

At the last follow-up visit, 74% of all eyes were able to achieve a best-corrected visual acuity of 20/50 or better. This level of improvement was more statistically significant with baring of DM (P = 0.005). Intraoperative perforation of DM occurred in 16 (13%) cases and was statistically significant in eyes with deep corneal scars (P = 0.012). However, this perforation did not seem to have an impact on the final visual acuity (P = 0.48). Main graft-related complications included graft-host vascularization (7/127), stromal graft rejection (4/127), graft infection (1/127), and persistent epithelial defect (1/127).

CONCLUSIONS

Deep lamellar keratoplasty provides a safer and successful alternative to penetrating keratoplasty for keratoconus patients but remains a challenging procedure. Endothelial graft rejection is absent after DALKP. However, stromal graft rejection, although very rare, does occur.

The effect of temperature on the antimicrobial activity of Optisol-GS

PURPOSE

To determine the survival of different bacteria inoculated in Optisol-GS at refrigerated storage temperature (6 degrees C) and after subsequent warming to room temperature (19-22 degrees C).

METHODS

Staphylococcus aureus, Enterococcus faecium, Streptococcus pneumoniae, and Pseudomonas aeruginosa were chosen from stock clinical isolates for inclusion in the study. The first group consisted of 12 Optisol-GS vials. The second group consisted of 12 Optisol-GS vials containing corneas inappropriate for transplantation according to the Eye Bank Association of America (EBAA) protocols. Each group was inoculated with 3 concentrations of approximately 10, 10, and 10 colony-forming units (CFU)/mL of each bacterial species and then refrigerated per EBAA protocol. After 48 hours of refrigeration, all vials were placed at room temperature (RT) and counts were performed at 48, 50 (2 hour RT), 54 (6 hour RT), 60 (12 hour RT), 72 (24 hour RT), and 96 (48 hour RT) hours. At 96 hours, the corneal tissue from 10 and 10 inocula were cultured. All samples underwent serial dilution, spiral plating on blood agar plates, and incubation at 35 degrees C. Viable colony counts were determined at 24 hours.

RESULTS

Except for the 10 CFU/mL inocula of P. aeruginosa, all isolates were viable after 48 hours of refrigeration. Rapid bactericidal activity was observed against P. aeruginosa after 2 hours at RT, with complete sterilization by 6 hours. The rate and extent of killing against S. aureus were influenced by the initial inoculum. Bactericidal activity was achieved after 2 hours at RT with 10 CFU/mL of S. aureus versus 24 hours with the 10 inoculum. Of note, bactericidal activity was not observed against S. pneumoniae and E. faecium following 24 hours of storage at RT. The presence of corneal tissue did not affect viable counts, with counts from corneal tissue cultures reflecting the counts seen from Optisol-GS after 48 hours at RT.

CONCLUSIONS

The antimicrobial activity of Optisol-GS was reduced at refrigerated temperature and enhanced at RT. Bactericidal activity was not observed against E. faecium at either refrigerated temperature or RT.

Comparison of Chen Medium and Optisol-GS for human corneal preservation at 4 degrees C: results of transplantation

PURPOSE

To compare results after transplantation of donor corneas stored in Chen Medium (containing beta-hydroxybutyrate without sodium bicarbonate or chondroitin sulfate) to corneas stored in Optisol-GS medium (containing sodium bicarbonate and 2.5% chondroitin sulfate).

METHODS

We performed 32 consecutive penetrating keratoplasties with donor corneas stored at 4 degrees C in either Chen Medium or Optisol-GS by random assignment. Corneal thickness measurements were made at 1 day, 1 week, 3 weeks, 2 months, and 1 year postkeratoplasty. Specular microscopic images of the donor endothelium were obtained at the beginning of storage and 2 months and 1 year postkeratoplasty. The percentage of intact epithelium 1 day after keratoplasty and the graft epithelialization time were estimated by the surgeons. Donor rim cultures were performed.

RESULTS

No statistically significant differences in corneal thickness or endothelial cell loss between the corneas stored in the two media were found at any time, although differences of less than 12% cell loss or 0.09-mm thickness at 2 months or less than 25% cell loss or 0.10-mm thickness at 1 year could not be excluded with 90% certainty in this small series. The mean percentages of intact graft epithelium on day 1, 64% for Chen Medium and 65% for Optisol-GS, were not significantly different. Endothelial cell density 2 months postkeratoplasty was significantly decreased for corneas stored in both media. Endothelial cell loss at 2 months was directly correlated with storage time in both media.

CONCLUSIONS

After keratoplasty, no statistically significant differences in corneal thickness, epithelial survival, and endothelial cell loss were found between corneas stored in Chen Medium and Optisol-GS. Endothelial cell loss at 2 months was significantly correlated with storage time in both media.

In vitro comparison of Chen medium and Optisol-GS medium for human corneal storage

PURPOSE

To compare paired human corneas after storage at 4 degrees C in Chen medium (CM) and Optisol-GS medium (OM) for 7, 10, 14, and 21 days.

METHODS

One cornea of each pair from nine human donors was randomly stored in either CM or OM, with its mate cornea stored in the other medium. Three pairs of corneas were stored for 7 days and two pairs each were stored for 10, 14, and 21 days at 4 degrees C. Baseline corneal thickness measurements and endothelial photographs were obtained with a specular microscope. Corneal thickness measurements were also taken on days 7, 10, 14, and 21 of storage. At the end of storage, the corneas were warmed 2 hours before endothelial photographs were taken and were then placed in fixative. A corneal endothelial analysis system was used to compare changes in endothelial size and shape after storage. After fixation, the corneal endothelium was examined by scanning electron microscopy (SEM), and TdT-dUTP terminal nick-end labeling (TUNEL) assays with 4'6-diamidino-2-phenylindole (DAPI) counterstaining were performed on tissue sections of each cornea. A laser scanning confocal microscope and an automated digital analysis system were used to detect the presence of TUNEL-positive apoptotic cells in each cell layer and to determine keratocyte densities.

RESULTS

Mean corneal thickness at 0, 7, 10, 14, 21 days of storage was 0.69 +/- 0.05 mm, 0.69 +/- 0.06 mm, 0.73 +/- 0.08 mm, 0.87 +/- 0.04 mm, and 0.87 +/- 0.03 mm, respectively, for CM and 0.65 +/- 0.06 mm, 0.59 +/- 0.07 mm, 0.63 +/- 0.03 mm, 0.60 +/- 0.03 mm, and 0.69 +/- 0.02 mm, respectively, for OM (p < 0.0001). The mean decrease in endothelial cell density at the end of the 7-, 10-, and 14-day storage periods was 11 +/- 10% for the CM corneas and 5 +/- 5% for the OM corneas (p = 0.18). SEM showed an intact endothelial monolayer in all corneas. The mean percentages of TUNEL-positive cells in epithelium, stroma, and endothelium of CM-stored corneas were 4 +/- 4%, 2 +/- 3%, and 0.1 +/- 0.3%, respectively, and did not differ from the OM-stored corneal values of 4 +/- 3%, 2 +/- 4%, and 0.9 +/- 1.5%. The percentage of TUNEL-positive cells did not increase with storage time. Keratocyte density was 368 +/- 130 cells/mm2 for CM-stored corneas and 447 +/- 96 cells/mm2 for OM-stored corneas (p = 0.13).

CONCLUSIONS

Corneas stored in CM were thicker during storage than those stored in OM. The two storage media did not differ with respect to endothelial cell loss during storage or to the percentage of TUNEL-positive cells or keratocyte density at the end of the storage period.

The past twenty-five years in eye banking

PURPOSE

This review of milestones and challenges in eye banking describes efforts made by dedicated eye bankers to ensure the quality and quantity of corneal tissue for corneal blind patients over the last 25 years.

METHODS

This account is the result of the recollection of the author, discussions with eye bankers, and a review of the literature, public documents, and Eye Bank Association of America (EBAA) records.

RESULTS

A measure of the success of eye banking is the fact that corneal transplant surgery is now scheduled as an elective procedure. Corneal tissue has also enjoyed a stellar safety record. This is due in part to the establishment of comprehensive medical standards by the EBAA, the accreditation of eye banks, and the training and certification of eye bank technicians.

CONCLUSION

Advancements in eye banking over the last 25 years have improved the quality of life of several hundred thousand corneal blind persons in this country. More efforts must be made in the future to eliminate corneal blindness internationally.

Colorimetric indicators of microbial contamination in corneal preservation medium

PURPOSE

To compare acid-base and oxidation-reduction indicators and to investigate the effect of buffer and temperature on the colorimetric detection of microbial growth in corneal preservation media.

METHODS

Corneal preservation media containing gentamicin, without or with HEPES buffer, were prepared with either phenol red or AlamarBlue indicators (AccuMed International, Westlake, OH, U.S.A.). Both media were inoculated with Staphylococcus aureus, Streptococcus sanguis, Pseudomonas aeruginosa, Serratia marcescens, or Candida albicans and then incubated at 4 degrees C, 22 degrees C, or 35 degrees C. The pH or percent reduction were determined hourly for eight hours, then daily for one week.

RESULTS

The length of time before a confirmed change in pH or reduction occurred varied by microorganism, storage temperature, and buffering capacity. At 4 degrees C, none of the microorganisms caused a detectable pH change in buffered medium within one day after inoculation, although two bacterial species reduced AlamarBlue within four hours. At 22 degrees C and 35 degrees C, all bacteria except P. aeruginosa produced a pH shift within a few hours, and all tested bacterial species reduced AlamarBlue. For bacteria producing detectable pH changes, HEPES-buffered medium took longer to change than medium without HEPES. C. albicans was not detectable in HEPES-buffered medium at any temperature by phenol red and was only detectable by AlamarBlue after 2-3 days at 22 degrees C and 35 degrees C.

CONCLUSION

Acidic shifts in refrigerated corneal preservation medium do not occur during contamination by several microorganisms. AlamarBlue, a redox indicator, is more sensitive than phenol red in detecting some bacteria. C. albicans is not reliably detected by pH or redox indicators.

Shewannela putrefaciens endophthalmitis after penetrating keratoplasty

PURPOSE

To report a case of Shewannela putrefaciens endophthalmitis after penetrating keratoplasty.

METHODS

Case report. Vitreous of the recipient and the preservative medium of donor cornea were cultured.

RESULTS

Vitreous of the recipient eye and the donor eye corneal preservative medium both grew S putrefaciens. The patient failed to respond to intravitreal, topical, and systemic amikacin and cefotaxime. Vision was lost rapidly. Evisceration was performed.

CONCLUSION

Shewannela putrefaciens should be considered as a potential pathogen contaminating donor cornea. Shewannela putrefaciens endophthalmitis is devastating and responds poorly to medical treatment.