Comparison of Three Staining Methods for the Detection of Intestinal Microspora Spp

BACKGROUND This study aimed to compare three staining methods including: Calcofluor white, Chromotrope and Quick Hot Gram chromotrope used in diagnosis of intestinal microsporidial spores. METHODS One hundred and seventy five stool specimens were collected from patients referred to Laboratory of Intestinal Protozoology at the School of Public Health, Tehran University of Medical Sciences during 2012-2013. All of specimens were evaluated by nested PCR. The formalin-fixed stool samples were prepared from each specimen and dried at room temperature for 10 min, followed by 10 min methanol fixation. All the collected stool samples were evaluated blindly by calcofluor white, Chromotrope and Quick Hot Gram chromotrope staining methods separately. RESULTS Microsporidial spores were recognized using Chromotrope, Quick Hot Gram chromotrope and Calcofluor white, in16 of 18 (88.8%), 17 of 18 (94.4%) and 18 of 18(100%) samples that were positive by nested PCR respectively. Regarding 14 stool samples that were negative by nested PCR, 14 cases were negative by chromotrope and Quick hot Gram chromotrope and 13 samples were negative by Calcofluor white. One discordant sample interpreted as false positive. CONCLUSION Calcofluor white staining had the best performance for the detection of intestinal Microsprora spores and can be used as initial screen test for the detection of intestinal Microspora spp.