Comment on fungal tape lift reporting frameworks

Abstract

The microbiology of the built environment and its relationship to occupant health indoors is an increasingly active area of scholarship.1 For example, adverse human-microbe interactions are often claimed as the cause of sick-building syndrome-type complaints; while it is argued that different indoor habitats including inanimate surfaces confer selection pressure on common environmental fungi leading towards increasing virulence.2 In turn, measuring actual or suspect indoor fungal contamination is increasingly common especially on indoor damp surfaces3 or following water damage,4 and is an ongoing area of occupational health and safety and the focus of building disputes and litigation.5 While there are established metrics for assessing the microbiological component of air using viable colony counts or viable and non-viable fungal spore counts in units per cubic meter of air;6,7 there is some difficulty with how best to measure and report surface fungal contamination using tape lifts where there is no consensus unit used for reporting. The method of using sticky tape to transfer fungal colonies from one surface onto microscope slides was first reported for dermatophyte fungi in the 1970’s and later for other fungi.8,9 This was shown to be an excellent technique that preserved for example the conidium and conidiophore morphology. Many researchers still use sticky tape sampling to evaluate biological contaminants like indoor fungi.10‒12 while the method has proven valuable in criminal and civil forensics where mould growth or absence has been used as evidence linking people and objects with places;13 or for sampling of other contaminants like chemical threat agents.14 The commercial development of readily available and inexpensive tape lifts,15,16 offer a consistent sample area on a flexible plastic slide for the determination of mould, other microbial, settled bioaerosols, and inorganic dust contamination. However, the problem of ‘describing what is seen’ remains. This has a lot to do with the diversity of locations that samples may come from and from the type of information that is sought. Eight methods have been identified. Each has more or less merit depending on the amount and quality of fungal material versus background debris. The first aim of this comment is therefore to review the literature and offer an opinion about a standardized protocol for fungal surface testing using tape lifts. The second aim is to offer the analyst a flexible framework when choosing an appropriate qualitative or semi-quantitative reporting index that is matched both to the quality and objectives of the sampling. Usually the goal is to identify a healthy or unhealthy building microbiome and to guide the scope or validate any remediation effort that has or should or must occur (IICRC S500/S520/R520).17,18