Molecular typing of Pneumocystis jirovecii found in formalin-fixed paraffin-embedded lung tissue sections from sudden infant death victims

Abstract

Previous studies have provided histological evidence of an association between primaryPneumocystisinfection and sudden infant death syndrome (SIDS). The aim of this work was to determine the species of clusteredPneumocystisorganisms found in formalin-fixed paraffin-embedded (FFPE) lung tissue sections from Chilean sudden infant death (SID) victims. This approach needed first to optimize a DNA extraction method from such histological sections. For that purpose, the QIAamp DNA Isolation from Paraffin-Embedded Tissue method (Qiagen) was first tested on FFPE lung tissue sections of immunosuppressed Wistar rats inoculated with rat-derivedPneumocystis. Successful DNA extraction was assessed by the amplification of a 346 bp fragment of the mitochondrial large subunit rRNA gene of thePneumocystisspecies using a previously described PCR assay. PCR products were analysed by direct sequencing and sequences corresponding toPneumocystis cariniiwere found in all the samples. This method was then applied to FFPE lung tissue sections from Chilean SID victims.Pneumocystis jiroveciiwas successfully identified in the three tested samples. In conclusion, an efficient protocol for isolating PCR-ready DNA from FFPE lung tissue sections was developed. It established that thePneumocystisspecies found in the lungs of Chilean SID victims wasP. jirovecii.