Non-invasive monitoring of microbial contamination on graphic collections preserved in museums, libraries and archives

Biological aerosol in indoor environments, such as museums, libraries and archives, can represent a hazard both for artworks, due to the presence of microorganisms, and for the health of operators and visitors, due to their potential infectious, allergenic or toxic effects. The detection of microbial colonization of air and surfaces, based on morphological and molecular analysis, is of fundamental importance for a correct preventive conservation and sustainable fruition. The results of the monitoring on both manufacts (prints, drawings), showing alterations potentially related to biological systems (foxing) and on furniture (metal cabinets, shelves, boxes) have been performed in the Central Institute for Graphic Arts (Rome). Sampling on manufacts surfaces was carried out by two non-destructive and non-invasive techniques using nitrocellulose membranes and nylon membranes fragments. The goal was to settle two parameters: the Microbial Build-up (MB the total number of microorganisms accumulated on a surface in an unknown period of time prior to the sampling) and the Hourly Microbial Fallout (HMF the number of microorganisms that settle on a surface during one hour). The results for MB and HMF were expressed as cfu/square decimeter (dm2). Fungal and bacterial taxa were identified through molecular biology techniques. The qualitative and quantitative analysis of microbial contamination showed any risk for the conservation of graphic artworks examined. This investigation represents a contribution for assessing the microbial contamination of graphic collections kept in indoor environments, this work is part of a broader research project whose goal is the definition of standardized methods for preventive conservation of organic cultural heritage.