Comparison of methods to identify and monitor mold damages in buildings

Molds thrive in indoor environments challenging the stability of building materials and occupants’ health. Diverse sampling and analytical techniques can be applied in microbiology of buildings with specific benefits and drawbacks. We evaluated the use of two methods, microscopy of visible mold growth (tape lifts) and DNA metabarcoding of mold and dust samples (swabs), for mapping mold-damage indicator fungi in buildings in Oslo. Overall, both methods provided consistent results for mold samples, where nearly 80% of the microscopy-identified taxa were confirmed by DNA analysis. Aspergillus was the most abundant genus colonizing all materials, while some taxa were associated with different substrates: Acremonium with gypsum board, Chaetomium with chipboard, Stachybotrys with gypsum board and wood, and Trichoderma with wood. Based on DNA data, community composition was clearly different between mold and dust with a much higher alpha diversity in dust. Most genera identified in mold were also detected with a low abundance in dust from the same apartments. Their spatial distribution indicated some local spread from the mold growth to other areas, but there was no clear correlation between relative abundances and the distance to the damages. To study mold damages, different microbiological analyses (microscopy, cultivation, DNA and chemistry) should be combined with a thorough inspection of buildings. The interpretation of such datasets requires the collaboration of skilled mycologists and building consultants.