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Editor,—Organ culture is now the most common corneal preservation technique used in European countries. We evaluated sterility of organ cultured donor corneas at the time of surgery.
From December 1992 to March 1996, 396 consecutive corneas were organ cultured at our institution. Of these 396 corneas, 270 (68%) were grafted and 126 (32%) were discarded. Eyes were obtained by enucleation within 48 hours of death. At the eye bank, eyes were rinsed for 30 seconds with sterile water then immersed in a 1% povidone-iodine solution for 2 minutes.1 2 Eyes were then immersed in a 1% thiosulphate solution for 30 seconds and rinsed with sterile saline. Corneas were organ cultured in Inosol medium (Opsia, Toulouse, France) at +31°C for 2 to 5 weeks. Inosol contains penicillin (100 IU/ml), streptomycin (100 μg/ml), and amphotericin (0.25 μg/ml). The culture medium was renewed on day 14 and day 28. After organ culture, the corneas were incubated in Exosol deswelling medium at room temperature for 1 to 4 days.
Four days before the end of organ culture, a sample of the preservation medium was cultured on thioglycolate broth at 37°C and trypticase soy at 22°C for 14 days. Corneas were accepted for transplantation only when the medium remained clear and red after at least 2 weeks of organ culture with negative 48 hour cultures. At the time of transplantation, the corneo-scleral rim and a sample of deswelling medium were sent to the department of microbiology for culture. Specimens were inoculated in thioglycolate broth and incubated at 37°C for 7 days.
Nine per cent (36 of 396) of the corneas were discarded because of contamination during organ culture. Contamination was either bacterial (67%) or fungal (33%). Of the 24 isolated bacteria, 22 (92%) were resistant to penicillin and 14 (58%) were resistant to gentamicin. None of the 14 tested antibiotics was effective against the 24 bacteria. Bacterial contamination occurred on day 6.2 (SD 3.8, range 2–14). Fungal contamination occurred on day 7.6 (SD 4.3, range 3–14). No positive culture occurred when the preservation medium had remained clear and red during organ culture. The incidence of donor cornea contamination decreased with time. Seven of 49 corneas from donors who died of infectious disease were contaminated (14%) while 29 of 347 corneas from other donors were contaminated (χ2 1.18, p = 0.28). Corneo-scleral rims were sterile in 98.9% of cases (267 of 270) of the grafted corneas. Deswelling media were sterile in 100% of cases (270 of 270). The corresponding deswelling media were sterile. No endophthalmitis occurred after transplantation.
Little is known about the result of corneo-scleral rim cultures after organ culture. Most European eye banks do not culture corneo-scleral rims after surgery.3 Erbezci et al 4 found a 6.7% incidence of rim contamination after organ culture. The drawback of microbiological safety assessed with organ culture is a loss of corneas through contamination during preservation. The incidence of contamination decreases with the experience of the technicians and is dependent on the expertise of protocols followed within individual eye banks. Two previous studies3 5 reported either a 0.5% and a 4.5% incidence of contamination during organ culture.Organ culture at +31°C allows corneas to be grafted sterile in almost 100% of cases. The chance of grafting a contaminated cornea after organ culture (1.1% in our study) is lower than after corneal storage at +4°C as described in the medical literature (Table 1). This is of interest as the chance of endophthalmitis is dramatically increased when donor corneo-scleral rims are contaminated.6 9 It is of note that no endophthalmitis occurred after transplantation of these 270 organ cultured corneas.
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