Molecular detection and phylogenetic placement of a microsporidian from English sole (Pleuronectes vetulus) affected by X-cell pseudotumors

Flatfish tissue samples exhibiting X-cell pseudotumors were rested with a n umber of ribosomal DNA (rDNA) general primers in polymerase chain reactions (PCRs). Microsporidian primers resulted in the amplification of an rDNA fr agment and molecular phylogenetic analysis indicated that although the orga nism did not relate closely with any current microsporidian genera, it was most similar to Nucleospora salmonis and branched within the Enterocytozoon idae. Re-examination of the original tissues used for DNA extractions revea led the presence of putative microsporidian spores in PCR-positive samples. These observations reiterate the highly sensitive diagnostic feature of PC R, allowing detection of organisms overlooked by conventional methods and d emonstrate the occurrence of rare, coinfecting organisms.