Reliability of Transport Medium in the Laboratory Evaluation of Corneal Ulcers STEPHEN D. MCLEOD, MD, ABHA KUMAR, MD, VICKY CEVALLOS, MT, MUTHAIAH SRINIVASAN, MD, AND JOHN P. WHITCHER, MD ● PURPOSE: To compare the microbiological yield of corneal ulcer cultures established by direct inoculation of culture media vs indirect inoculation by means of trans- port medium (Amies without charcoal). ● DESIGN: Single masked, prospective clinical trial. ● METHODS: Scrapings were obtained for Gram and potassium hydroxide (KOH) stains from eyes with pre- sumed infectious keratitis and cultured by direct plating onto standard media. Samples were also held in transport media (Amies without charcoal) at room temperature and then plated after 4 and 24 hours. Yields from direct plating vs cultures by means of transport media were compared. ● RESULTS: Of 100 consecutive eyes examined with presumed infectious keratitis, Gram or KOH stain re- vealed a bacterial or fungal agent in 69 cases (69%). Of these, 26 were bacterial and 43 fungal. Twenty-two bacterial infections produced positive cultures by direct plating, and all produced the same organism with Amies medium after 4 and 24 hours, respectively. For 43 fungal infections identified by KOH stain, 29 (67%) yielded a positive result after 4 hours in Amies transport medium and 27 (63%) after 24 hours in Amies medium. A total of three cases (7%) that showed fungal infection on KOH stain but did not yield organisms by direct plating did so after inoculation with Amies transport medium. For all comparisons, there was no difference in recovery rates by means of transport medium compared with direct plating (McNemar exact P > .05). ● CONCLUSIONS: In the clinical setting, Amies transport medium may be a useful alternative to direct inocula- tion onto blood agar for the laboratory evaluation of infectious keratitis. (Am J Ophthalmol 2005;140: 1027–1031. © 2006 by Elsevier Inc. All rights re- served.) S EVERE INFECTIOUS KERATITIS CAN LEAD TO MARKED visual impairment, and the identity and antimicro- bial susceptibility profile of the offending organism can be helpful in directing appropriate therapy. However, presumably on the basis of the relatively high success rates of empirical therapy using modern ophthalmic fluoroquin- olone preparations, it is increasingly uncommon for phy- sicians in the United States to obtain specimens for laboratory evaluation before initiating treatment. 1 A na- tionwide survey of practice patterns in the evaluation of infectious keratitis suggested that particularly if the ulcer was not initially considered severe, less than 50% of practitioners maintained supplies for direct inoculation of culture plates or would obtain cultures before initiating treatment. 2 Empirical treatment that does not rely on laboratory identification of the organism has a high like- lihood of success if the initial antibiotic chosen is widely effective against prevailing infectious agents. However, in the event that resistant organisms are encountered and antibiotic therapy must be changed, without the benefit of microbiological information, it is difficult to make a rational therapeutic decision. The documented emergence of resistant patterns to fluoroquinolones in ophthalmic use 3,4 is therefore accom- panied by decreasing confidence in empirical therapy and by greater need for strategies for the microbiological evaluation of infectious keratitis that are simple, reliable, and cost-effective. 5 A key element of such a strategy is the initial culture. However, as noted, few practices maintain the necessary supplies for the direct plating of corneal scrapings, which remains the gold standard for laboratory evaluation. This has been attributed to the expense of maintaining a complete set of culture media, and the time-consuming process of scraping and inoculating vari- ous media in the clinic. 1,2,5 As an alternative to maintaining numerous media and direct plating of corneal scrapings, some authors have suggested that scrapings introduced to transport medium Accepted for publication Jun 16, 2005. From the Department of Ophthalmology at the University of Califor- nia at San Francisco, San Francisco, California (S.D.M., J.P.W.), the Francis I. Proctor Foundation, San Francisco, California (S.D.M., A.K., V.C., J.P.W.); and the Aravind Eye Hospital, Tamil Nadu, India (M.S.). Supported in part by unrestricted grant from Research to Prevent Blindness Inc, New York, and an unrestricted grant from the South Asia Research Fund. These agencies had no role in the design and conduct of the study; collection, management, analysis, or interpretation of the data; or preparation, review, or approval of the article. Inquiries to Stephen D. McLeod, MD, University of California San Francisco, 10 Koret Way, K-304, San Francisco, CA 94143; fax: (415) 476-2896; e-mail: mcleods@itsa.ucsf.edu © 2006 BY ELSEVIER INC.ALL RIGHTS RESERVED. 0002-9394/05/$30.00 1027 doi:10.1016/j.ajo.2005.06.042