Comparison of histopathological analysis, culture and polymerase chain reaction assays to detect mucormycosis in biopsy and blood specimens

The aim of this study was to compare direct microscopic examination with culture and PCR for the diagnosis of Mucorales infection in blood and tissue specimens. Blood samples and tissue specimens were obtained from 28 patients (total 58 samples) with suspected invasive fungal infection and cultured on proper media. Direct smear of tissue samples was done with potassium hydroxide, hematoxylin and eosin, and methenamine silver staining. DNA extracted from blood and tissue specimens were used for semi-nested PCR targeting 18S rDNA of Mucorales species. Mucormycosis was documented in 7/28 (25%) of tissue specimens with positive findings by direct smear, of which PCR and culture were positive in 6 (86%) and 5 (70%) specimens, respectively. The etiologic agents were Mucor spp. and Rhizopus spp. However, culture and PCR results for all blood specimens were negative. As the orders of Mucorales do not have well growth in culture media, PCR with tissue specimens is more sensitive than tissue or blood culture methods. Unfortunately, there is no alternative method for direct smear, which is an invasive method. Molecular methods may be helpful in these cases.