Syncephalastrum racemosum

The genus Syncephalastrum is characterised by the formation of cylindrical merosporangia on a terminal swelling of the sporangiophore. Sporangiospores are arranged in a single row within the merosporangia. Syncephalastrum racemosum is the type species of the genus and a potential human pathogen; however, well-documented cases are lacking. It is found mainly from soil and dung in tropical and subtropical regions. It can also be a laboratory aerial contaminant. The sporangiophore and merosporangia of Syncephalastrum species may also be mistaken for an Aspergillus species, if the isolate is not examined carefully.

RG-2 organism

Syncephalastrum microscopy

Terminal vesicle, merosporangia and sporangiospores of Syncephalastrum racemosum.

Morphological description: 
Colonies are very fast growing, cottony to fluffy, white to light grey, becoming dark grey with the development of sporangia. Sporangiophores are erect, stolon-like, often producing adventitious rhizoids, and show sympodial branching (racemose branching) producing curved lateral branches. The main stalk and branches form terminal, globose to ovoid vesicles which bear finger-like merosporangia directly over their entire surface. At maturity, merosporangia are thin-walled, evanescent and contain five to ten (up to 18) globose to ovoid, smooth-walled sporangiospores (merospores). Maximum growth temperature 40C.

Key features: 
Mucorales, producing sympodially branching sporangiophores with terminal vesicles bearing merosporangia.

References: 
Domsch et al. (1980), McGinnis (1980), Onions et al. (1981), Rippon (1988), Samson et al. (1995), de Hoog et al. (2000, 2015), Ellis (2005b).

Antifungal susceptibility: Syncephalastrum racemosum very limited data (Australian national data); MIC µg/mL.
Antifungal No 0.016 0.03 0.06 0.125 0.25 0.5 1 2 4 8
AMB 5       2 2 1        
VORI 5             1   4  
POSA 5       2 2 1        
ITRA 5       2 2 1