Articles
POTTING MIXES – RESERVOIRS OF HUMAN FUNGAL PATHOGENS
These fungi cause mycetomas and chronic superficial and systemic infections of the central nervous and respiratory systems.
As the incidences of serious mycotic infections caused by S. apiospermum and S. prolificans are increasing in Australia, there is a need to develop an effective technique to isolate them from the environment in order to ascertain their frequency.
This is especially so from potting mixes, as they are increasingly associated with the environment of hosts, susceptible to fungal infections.
A commercial potting mix, containing composted pine bark, peat and sewage-sludge, was inoculated with S. apiospermum in chopped Potato Dextrose Agar (PDA). The fungus was successfully isolated after 14 days incubation of the mix at 28°C. The antibiotics streptomycin, chloramphenicol and amphotericin B were shown not to suppress the growth of S. apiospermum and S. prolificans and could therefore be used in isolation media.
Other antibiotic agents, namely furalaxyl, cycloheximide, and octoxynol at high concentrations in PDA, were shown to suppress growth of some strains of S. apiospermum and S. prolificans. An incubation temperature of 30–35°C may be more selective for the recovery of these fungi from the natural environment, as maximal colony growth of pure culture occurred on PDA at these temperatures.