is a cosmopolitan filamentous fungus which is commonly isolated from rural
soils, from polluted water, from composts, and from manure of cattle and
fowl. Scedosporium occasionally causes infections in humans.
Scedosporium contains two species namely, Scedosporium apiospermum
and Scedosporium prolificans. There is no sexual form or teleomorph
known for Scedosporium prolificans while Pseudallescheria boydii
is the teleomorph of Scedosporium apiospermum.
Pathogenicity and Health Effects
immunocompetent and immunocompromised hosts can be infected by
Scedosporium prolificans. Subcutaneous infections,
arthritis are commonly post – traumatic and may affect otherwise healthy
Due to various
reasons, on the other hand, disseminated infections which are often fatal
are generally encountered in immunosuppressed neutropenic patients.
Scedosporium prolificans is now the known common causative agent of
disseminated phaeohyphomycosis. Scedosporium prolificans has
been reported to cause ocular infections (keratouveitis) and
colonization. Cases with
have also been reported.
Growth rate is very rapid at 25°C
and colonies are
initially cottony and moist (yeast – like) becoming flat with fine, short,
mycelial tufts in texture in maturation; and
surface colony color is light gray to black becoming dark gray to black in
time while reverse is gray to black;
Septate hyaline hyphae, conidiogenous cells (annellides), and conidia are
Annellides may form directly from hyphae or are formed at the tips of the
conidiophores, flask – shaped with swollen base part and elongated neck;
Conidia are oval – shaped, olive to brown in color, with a slightly
narrowed, truncated base, unicellular, with size of 2 – 5 x 3 – 13 µm, and
appear in clusters at the tips of the annellides; Additionally, some
isolates may produce round, thick – walled conidia which are formed
directly from the hyphae (present in Scedosporium asexual state);
After two to three weeks of incubation, brown cleistothecia are often
present in the sexual state of Pseudallescheria boydii.
precautions are required, no special safety measures needed.
is resistant to amphotericin B, flucytosine, ketoconazole, miconazole,
fluconazole, and itraconazole. Showed no or very limited in vitro
activities against Scedosporium prolificans isolates are
voriconazole, the novel triazole Syn – 2869 and caspofungin.
Although either itraconazole
or terbinafine has no activity against most isolates of Scedosporium
prolificans, the combination of these two drug agents proved to be
active in in vitro
95% of the
isolates after 48 hours of incubation. Additionally, in this combination
study antagonism was not observed.
infections caused by Scedosporium prolificans is difficult due to
its primary multi – resistant nature. Therapy of amphotericin B alone or
in combination with flucytosine, fluconazole, or itraconazole has been
used in Scedosporium prolificans - infection cases. The mortality
rate, however, has been very high in most disseminated infection cases.
Liposomal amphotericin B combined with G - CSF seemed to improve survival
in an immunocompromised murine model with disseminated Scedosporium
prolificans infection. Post – traumatic infections which include
arthritis in immunocompetent cases have responded to fluconazole or
surgical debridement alone.
Optimal treatment of Scedosporium prolificans infections remains
yet unidentified and there is a great demand for novel agents with
positive activity. Significantly, the clinical outcome is closely linked
with the immune status of the host, degree of the infection, and viability
of concomitant surgical debridement.
Finally, optimal treatment of Scedosporium prolificans infections
remains yet unknown and there is a great demand for novel agents with
favorable activity. Significantly, the clinical outcome is closely
associated with the immune status of the host, extent of the infection,
and feasibility of concomitant surgical debridement.