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36 Cornea microbiology contamination rate depending on post mortem time, retrospective analysis at croatian tissue
Marina Roncevic Krajina1, Ivana Vidovic1, Branka Golubic Cepulic1
1University Hospital Centre Zagreb, Croatian Tissue and Cell Bank, Zagreb, Croatia.
Background:
Corneas procured post mortem are at risk of microbiology contamination, therefore decontamination procedures before storage, aseptic techniques during processing and antimicrobials used in the storage medium are routinely used. Despite that, corneas are discarded due to microbiology contamination. According to professional guidelines, corneas can be procured preferably within 24 hours after cardiac arrest but up to 48 hours. Our goal was to evaluate the risk of contamination depending on the post mortem time and the spectrum of microbes isolated.
Methods:
Corneas were decontaminated before procurement using 0,5% povidone iodine and tobramycin, stored in the organ culture medium and microbiologically tested after four to seven days of storage. Ten millilitres of cornea preservation medium were inoculated in two blood bottles (aerobic, anaerobic/fungi, Biomeriex) and incubated for seven days.Microbiology testing results in the period of four years (2016-2020) were retrospectively analysed. Corneas were divided in four groups depending on the duration of post mortem interval: group A post mortem interval < 8 h, group B post mortem ranging from 8 to 16 h, group C post mortem ranging from 16 to 24 h and group D post mortem > 24 h. Contamination rate and spectrum of isolated microorganisms in all four groups were analysed.
Results:
1426 of 2019 procured corneas were stored in organ culture and microbiologically tested. 65/1426 of tested corneas were contaminated (4,6%). In total, 28 strains of bacteria and fungi were isolated.Contamination rate of post mortem groups are as following: group A 3,1% (14/455), group B 4,1% (23/561), group C 6,7% (27/402) and group D 12,5% (1/8).In the group A bacteria family Staphylococcaceae, Moraxellaceae, Morganellaceae were predominately isolated (64,3%). In the group B fungi Saccharomycetaceae, bacteria Moraxellacea, Staphylococcaceae, Morganellaceae and Enterococcaceae were predominately isolated (78,1%). In the group C, bacteria family Enterococcaceae, Moraxellaceae and fungi Saccharomycetaceae are most often isolated (70,3%). In the group D bacteria family Enterobacteriaceae was isolated (100%).
Conclusion:
Organ culture allows detection and discard of microbiology contaminated corneas. Our results show higher microbiology contamination rate for corneas with longer post mortem intervals, suggesting these contaminations can be rather related to donor post mortem changes and contamination than previous infection. In order to keep the best quality and safety of the donor cornea, all efforts should be directed in disinfection of the cornea and keeping post mortem interval shorter.
Insights
Corneal contamination risk increases significantly with longer post mortem intervals. Shorter post mortem times and thorough disinfection are crucial for maintaining donor cornea quality and safety.
Area of Science:
- Ophthalmology
- Microbiology
- Transplantation Science
Background:
- Post mortem corneal procurement carries a risk of microbial contamination.
- Standard procedures include decontamination, aseptic techniques, and antimicrobial storage media.
- Despite precautions, some corneas are discarded due to contamination.
Purpose of the Study:
- To evaluate the relationship between post mortem interval and microbial contamination rates in donor corneas.
- To identify the spectrum of microorganisms isolated from contaminated corneas based on post mortem time.
Main Methods:
- Retrospective analysis of microbiology testing results from 1426 corneas over four years (2016-2020).
- Corneas were categorized into four groups based on post mortem intervals (<8h, 8-16h, 16-24h, >24h).
- Microbial cultures were performed after 4-7 days of storage in organ culture medium.
Main Results:
- Overall contamination rate was 4.6% (65/1426 corneas).
- Contamination rates increased with post mortem interval: 3.1% (<8h), 4.1% (8-16h), 6.7% (16-24h), and 12.5% (>24h).
- Predominant isolates varied by group, including Staphylococcaceae, Moraxellaceae, Morganellaceae, Saccharomycetaceae, Enterococcaceae, and Enterobacteriaceae.
Conclusions:
- Organ culture effectively detects and allows discarding of contaminated corneas.
- Longer post mortem intervals are associated with higher contamination rates, likely due to post mortem changes rather than pre-existing infection.
- Optimizing donor cornea quality and safety requires rigorous disinfection and minimizing the post mortem interval.