Bioburden assessment by passive methods on a clinical pathology service in one central hospital from Lisbon: what can it tell us regarding patients and staff exposure?

Project EXPOsE. Project nº 23222 (02/SAICT/2016).The assessment and control of microbial contamination in healthcare facilities is presently a mandatory and vital part of strategies to prevent and control hospital-acquired infections. This study aims to assess the bioburden with two passive sampling methods (30 ventilations grids swabs and 16 electrostatic dust collectors (EDCs)) at Clinical Pathology Services. The fungal burden was characterized through molecular tools, antifungal resistance, and the mycotoxins and cytotoxicity profile. Total bacteria presented the highest prevalence in both matrixes, whereas Gram-bacteria presented the lowest. Swabs presented a higher prevalence (27.6%) for fungal burden. Chrysonilia sitophila presented the highest prevalence in swabs, whereas for EDCs, C. sitophila and Mucor sp. were the most prevalent. Concerning Aspergillus genera on swabs, section Flavi was the one with the highest prevalence (58.02%), whereas, for EDCs, section Versicolores was the only section observed (100%). Aspergillus section Fumigati was detected in 10 swabs and 7 EDC samples and Aspergillus section Versicolores were detected in one EDC sample. Fungal growth on azole-supplemented media was observed in eight EDC samples. No mycotoxins were detected in any of the samples. A low cytotoxic effect was observed in two sites upon incubation of collected samples with A549 and SK cells and in two other sites upon incubation of collected samples with SK cells only. A medium cytotoxic effect was observed with one EDC sample upon incubation with A549 cells. This study reinforces the need for determination of the azole resistance profile for fungal species and allowed a preliminary risk characterization regarding the cytotoxicity. An intervention including the use of ultraviolet with a wavelength between 200 nm and 280 nm (UVC)—emitting device and increased maintenance and cleaning of the central heating, ventilation, and air conditioning (HVAC) systems should be ensured to promote the reduction of microbial contamination.