Isolation and clinical significance of Pseudallescheria and Scedosporium species

In the course of the past decades, Pseudallescheria/Scedosporium species have become increasingly recognized as causative agents of significant infections in humans. In our laboratory in Bonn, Germany, the first clinical strain was isolated by chance by dipping a wooden swab taken from a chronic wound process into brain-heart infusion broth. The latter was being used as an enrichment medium for the recovery of infectious agents. Subsequently, a total of 35 additional Pseudallescheria/Scedosporium strains from four patients suffering from invasive fungal infection were isolated with this method. In contrast, only 27 of the 36 isolates were detected by plating the specimens on Sabouraud glucose agar (75%). Furthermore, eight strains were recovered from the respiratory tract samples of six out of 42 patients suffering from cystic fibrosis. While all eight strains were isolated on SceSel+ agar, only five were obtained from wooden sticks dipped into broth for enrichment of infectious agents (62.5%) and only three on Sabouraud glucose agar (37.5%). The clinical cases are summarized and methods used for detection are described. Species identification is based on the taxonomy valid in 2005; in the interim several re-classifications have been proposed.