Sunday, 21 October 2012
Scedosporium prolificans -Fungus (Previously known as Scedosporium inflatum)
Ecology: Scedosporium prolificans is a cosmopolitan fungus isolated primarily from soils (saprophyte), however its ecosystem and distribution may be more restricted than the other major species, Scedosporium apiospermum. Scedosporium prolificans has been isolated from hospital settings after the environment was disturbed during on-site construction.
Macroscopic Morphology: S.prolificans exhibits moderately rapid spreading growth and will mature within 5 to 7 days at 25oC on sabouraud dextrose agar (SDA or SAB). Young suede-like to downy growth becomes increasingly cottony as it develops an olive-grey to a black colouration. Light coloured mycelial tufts may develop as the colony ages. Reverse is a dark brown to dark grey, almost black in appearance.
Scedosporium prolificans SAB, 72 hrs, 30oC
Microscopic Morphology: Scedosporium prolificans produces hyaline septate hyphae from which conidiogenous cells are produced along the length. The conidiogenous cells are flask-shaped annellides which have a swollen base (inflated) from which extends an elongated 'neck'. Conidia are produced singly or in small groups at the apex of the annellide. The smooth walled single-celled conidia are hyaline to a pale brown in colour and are oviod to pyridaform in shape. These conidia (annelloconidia) have a truncated base where they were attached to the conidiogenous annellide. The conidia measure 2 - 5 μm to 3 - 13 μm (average 3.4 μm to 5.3 μm) in dimension.
Note: All photographs which follow were taken using the Leica DMD-108 digital microimaging device.
Scedosporium prolificans (LPCB, 250X) -First impression of a slide culture.
Scedosporium prolificans -hyphae with conida visible. Conidiogenous cells not all that distinct at this magnification, (LPCB, 400X)
Scedosporium prolificans -another view of conidia along hyphae
Scedosporium prolificans - conidia seen distributed singly and in clusters along the hyphae. (LPCB, 400X)
Scedosporium prolificans - At this magnification the conidiogenous cells are becoming more obvious. Ovoid to pyridaform conidia can be seen attached at the apex of the annellide. Note 100 micron bar at upper right. (LPCB, 400+10X)
Scedosporium prolificans - Here we can see a conidiogenous cell (annellide) extending from the hyphae at which four annelloconida can be seen at the apex. (LPCB, 1000X)
Scedosporium prolificans - hyphae with annellides bearing ovoid to pyridaform annelloconidia. (LPCB, 1000X)
Scedosporium prolificans - Here we can distinctly see the inflated, vase-like annellide conidiophore (arrows) from which are produced the annelloconidia. (LPCB, 1000X)
Scedosporium prolificans - Here we can see the elongated 'neck' (1) at the apical end of the annellide and the truncated base or scar at the end of the annelloconidia where it was once attached (2). The swollen or inflated vase like base is evident just right of (1) where the conidiogenous cell attaches to the hyphae. (LPCB, 1000X)
Scedosporium prolificans - Here again we can see the elongated 'neck' (1) with an annelloconidia at the apex, the inflated annellide (2) and the annelloconidia, each with a flattened, truncated base of attachment (3).
Scedosporium prolificans - Measurement of annelloconidia - 7.0 μm to 7.4 μm in length, 4.7 μm in diamenter in this field. (LPCB, 1000+10X)
Scedosporium prolificans - small clusters of conidia (annelloconidia) at the apex of annellides (conidiogenous cells) extending from hyphae.
Scedosporium prolificans - one last photo showing branched septate hyphae with annelloconidia at apex of annellides. (LPCB, 1000+10X)
Pathogenicity: Scedosporium prolificans is an emerging fungal pathogen can infect both immunocompetent and immunocompromised individuals. Noted risk factors for scedosporiosis have included malignancy, cystic fibrosis as well as solid organ transplantation. Onychomycosis and mycotic keratitis have been reported in the literature. Inhalation of the fungus has resulted in colonization of the paranasal sinus and the lungs. Penetrating injuries may result in localized infections of the joints resulting in septic arthritis as well as osteomyelitis. Disseminated have been reported in immunosuppressed patients such as those experiencing prolonged neutropenia and post-transplantation therapy. Accurate identification is imperitive as S.prolificans exhibits increased resistance to common antifungal medications and disseminated infections is often fatal even in immunocompetent patients. Asymptomatic colonization as also been reported.
Differentiation: Scedosporium prolificans can be differentiated from Scedosporium apiospermum as the former has a distinctive swollen (inflated) base. This inflated base was the reason this fungus was previously known as Scedosporium inflatum. S.prolificans produces annellides that are flask-shaped, unlike the cylindrical conidiogenous cells of S.apiospermum. S.prolificans is inhibited by media containing cycloheximide. Finally, S.prolificans has no sexual stage (telemorph) as does Scedosporium apiospermum/Pseudallescheria boydii.
* * *