Association between positive corneal rim cultures and microbiology screening protocols in Ontario.

Objective: (i) To assess the rate of positive microbiological cultures of corneas prepared by the Eye Bank of Canada (Ontario Division) between January 1, 2012, and December 31, 2013; (ii) to review the microbiology protocols at the 5 major transplant centres in Ontario; and (iii) to assess the incidence of endophthalmitis during the study period.

Design: Retrospective chart review.

Participants: A total of 4186 consecutive cultured corneal tissues prepared by the Eye Bank from January 1, 2012, to December 31, 2013.

Methods: Rates of culture-positive cornea rims and incidence of postkeratoplasty endophthalmitis at 5 surgical centres in Ontario were determined, and the protocols used to culture rims at each site were concurrently reviewed. Culture results were analyzed via logistic regression for positive cultures.

Results: The rate of positive cultures at each sites were as follows: centre A, 3.74%; centre B, 3.26%; centre C, 0.51%; centre D, 0.48%; and centre E, 0.04%. Centres A, B, and D were noted to have significantly higher positive rates than centre E. In comparing microbiology protocols, longer incubation period (11 days) was 12 times more likely to be associated with higher positive culture rates than shorter period (4-5 days). Six-month follow-up of all keratoplasties revealed zero reported cases of endophthalmitis.

Conclusions: A literature review regarding the predictive value of routine culturing reveals conflicting data. Our findings suggest that differences in the microbiology protocols directly influence the rates of positive rim cultures. Without a standardized protocol, it is not possible to evaluate the predictive value of routine corneal rim culturing in predicting postkeratoplasty endophthalmitis.