Question: I had some mold samples tested through a lab here in the US. The results returned showing Aspergillus 19 colonies for the first sample. The second sample results were Aspergillus 3 colonies, Geotrichum 1 colony, and Penicillium 1 colony. What are colonies and what does the number of them stand for? There is a serious problem in our home and none of us is doing great health wise. Any info you could give me would be very much appreciated.
Answer: In biology, a colony (from Latin colonia) refers to several individual organisms of the same species living closely together. In case of mould, colonies refer to individual growths (see picture). The number of colonies is a count of those individual growths (colonies) and they may belong to different types of mould or same type. For example in your case the first sample had only Aspergillus (19 colonies) and the second sample had 3 different types of mould. That’s Aspergilus (3 colonies), Geotrichum (1 colony) and Penicillium (1 colony). The picture on the right shows colonies of 2 different types of moulds. The blue-green colonies belong to Penicillium and the rest (with greenish centers) are Stachybotrys colonies.
The number of colonies reported for the 2 samples do not appear to be high but this does not mean you don’t have a mould problem. You may want to seek help from a qualified local environmental consultant who may be able to assess the extent of mould growth in your home and advise you on what to do.