Bacterial contamination of human organ-cultured corneas

This study was designed to define the risk of contamination of human corneas preserved by the organ-culture method.

We examined the microbial contaminations in 3,100 corneoscleral rims cultivated in our eye bank. Microbiologic tests were performed in the preservation medium 5 days after the beginning of cornea cultures and in the last day of culture (21.5 +/- 8.1 days), when the corneas were transferred to the deswelling medium. In 1,029 corneas a microbiologic test also was performed 1 day after the beginning of deswelling procedure.

We found 206 microbial contaminations (6.65% of total) after 5 days and 17 (0.55%) at the end of the preservation period. The total number of contaminated samples during the cornea culture was 223 corresponding to 7.2% of the samples (95% confidence interval, 6.3-8.1). The 1,029 tests performed during the deswelling step disclosed 26 contaminated cornea cultures despite apparent sterility of the medium (2.5%; 95% confidence interval, 1.5-3.5).

The observation of microbial contaminations in a time close to the transplant (i.e., at the end of the preservation period and in the deswelling step) showed that a fast microbial tests during the deswelling procedure may prevent the grafting of a contaminated cornea. The appearance of bacteria in the deswelling medium despite a negative culture medium suggests that bacteria penetrate the corneal tissues during the culture to be subsequently extruded when the internal fluids move outward.