Purchase this article with an account.
M.D. Bernal, V. Cevallos, J.P. Whitcher, T. Lietman, K. Chern; The Probability of Finding the Pathogen of Presumed Microbial Keratitis With Repeat Cultures After a Negative Culture at the F.I. Proctor Foundation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3561.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
When faced with a negative culture for presumed microbial keratitis, repeat cultures are often obtained. In this report, we determine whether a second culture after an initial negative result increases diagnostic yield
Retrospective cohort study. The results of corneal cultures for presumed microbial keratitis seen at F.I. Proctor Foundation since 1996 with an initial negative culture result will be reviewed. The percentage of positive repeat corneal cultures was determined.
Corneal cultures were taken from 699 patients with presumed microbial keratitis from January 1996 until October 2005 at the F.I. Proctor Foundation. 31 of these 699 patients had an initial negative corneal culture and one or more subsequent corneal cultures within 60 days of the first culture. Nine of the 31 (29%) patients had a positive second corneal culture (1 fungal, 2 parasites, 6 bacteria). Fifty–five percent (5/9) of the repeat positive cultures were taken 26 or more days after the initial negative culture and all of these grew bacteria. The other repeat positive cultures (45%, 4/9) were taken one to ten days after the initial culture. Of these four, two grew parasites, one fungi and one bacteria. Early repeated cultures were far more likely to yield non–bacterial organisms (p=0.048, Fisher’s Exact).
No previous reports to our knowledge have studied the utility of repeating corneal cultures for presumed microbial keratitis. The yield of repeated corneal cultures at our institution appears relatively low. However, repeated cultures that were drawn early and were positive were more likely to grow fungi or parasites while those that were drawn late were more likely to grow bacteria; in both of these situations the results of these positive cultures are likely to alter therapy. Larger studies will be needed to clarify the cost–effectiveness of repeating corneal cultures for presumed microbial keratitis.
This PDF is available to Subscribers Only