Effect of using multiple culture media for the diagnosis of noninvasive fungal sinusitis

Abstract

Background: This study was designed to assess the relative efficiency of three different culture media for isolating fungi in patients suspected of having noninvasive fungal sinusitis. Methods: A prospective study was performed of 209 operative samples of sinus "fungal-like" mucin from 134 patients on 171 occasions and processed for microscopy and fungal culture in Sabouraud's dextrose agar, potato dextrose agar, and broth media. Results: Ninety-three (69%) of 134 patients had evidence of fungal infection. Two-thirds of patients had negative microscopy samples yet 56% of these went on to positive cultures. Forty-five percent cultured Aspergillus genus. Discrepancy between the fungi cultured in different media and on different occasions was common. With a single culture medium up to 19% of patients and 15% of samples would have been falsely labeled fungal negative. Conclusion: Increasing the number and type of fungal culture media used increases the number and range of fungal isolates from mucin in patients with the features of fungal sinusitis. Negative specimen microscopy is unreliable. All specimens should be cultured in multiple media and on multiple occasions when fungal sinusitis is suspected.