Laser Scanning Confocal Microscopy Was Used to Validate the Presence of or in Formalin-Fixed Paraffin Embedded Tissues.

and are Gram-negative, facultative intracellular bacteria that cause melioidosis and glanders, respectively. Currently, there are no vaccines for these two diseases. Animal models have been developed to evaluate vaccines and therapeutics. Tissues from infected animals, however, must be fixed in formalin and embedded in paraffin (FFPE) before analysis. A brownish staining material in infected tissues that represents the exopolysaccharide of the pathogen was seen by bright field microscopy but not the actual microorganism. Because of these results, FFPE tissue was examined by laser scanning confocal microscopy (LSCM) in an attempt to see the microorganism. Archival FFPE tissues were examined from ten mice, and five nonhuman primates after exposure to or by LSCM. Additionally, a historical spleen biopsy from a human suspected of exposure to was examined. was seen in many of the infected tissues from mice. Four out of five nonhuman primates were positive for the pathogen. In the human sample, was seen in pyogranulomas in the spleen biopsy. Thus, the presence of the pathogen was validated by LSCM in murine, nonhuman primate, and human FFPE tissues.