Is inclusion of Sabouraud dextrose agar essential for the laboratory diagnosis of fungal keratitis?

• Main Authors: Das Sujata, Sharma Savitri, Kar Sarita, Sahu Srikant, Samal Bikash, Mallick Aparajita
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2010-01-01
• Series: Indian Journal of Ophthalmology
• Subjects: Blood agar; chocolate agar; diagnosis; fungal keratitis; Sabouraud dextrose agar
• Online Access: http://www.ijo.in/article.asp?issn=0301-4738;year=2010;volume=58;issue=4;spage=281;epage=286;aulast=Das
• ISSN: 0301-4738; 1998-3689

<b>Purpose:</b> To determine whether the inclusion of Sabouraud dextrose agar (SDA) is essential in the diagnosis of fungal keratitis. <b> Materials and Methods:</b> Corneal scrapings of 141 patients with microbial keratitis were smeared and cultured. Sheep blood agar (BA), chocolate agar (CA), SDA, non-nutrient agar (NNA) with <i>Escherichia coli </i>overlay, and brain heart infusion broth (BHI) were evaluated for time taken for growth and cost. The media were also evaluated experimentally for rate of growth and time taken for identification. <b> Results:</b> Twenty-six of 39 patients positive for fungus in corneal scrapings by microscopy were culture-positive. Fungus grew on BA in 22/39, on CA in 18/39, on SDA in 17/39, on NNA in 17/39, and on BHI in 13/39 cases. Growth on SDA was higher in ulcers with larger infiltrate (6/18 versus 9/13, <i>P</i> = 0.04). Estimated saving with inclusion of only BA/CA was Rs. 600 per patient. Performance of all media was similar in <i>in vitro</i> experiment although the characteristic spores and color were seen earlier on SDA. <b> Conclusion:</b> Fungal keratitis can be reliably confirmed on BA or CA, which support growth of both bacteria and fungus.