Bacterial and fungal load quantitative and qualitative assessment of indoor air in Portuguese long-term and acute healthcare settings

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Abstract Background In healthcare-associated infections, the major transmission route is assumed to be the direct or indirect contact between patients, staff, and the environment. However, little is known about the air role as a pool for pathogens and multidrug resistance (MDR) in healthcare settings. The aim of this study was to quantitatively and qualitatively compare microbial air quality in a Portuguese long-term healthcare unit (LTHU) and a central hospital (CH). Methods During 2021 and 2022, air samples were collected fortnightly in both settings and their microbial load (bacteria and fungi) was determined (colony forming units – CFU/m3). Sampled sites were classified according to area, room capacity and occupation, activity and related infection potential risk. Bacterial isolates were randomly selected for identification by Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry, antimicrobial susceptibility testing and polymerase chain reaction (PCR) screening of extended-spectrum beta-lactamases and metallo-beta-lactamases genes. Results A total of 192 air samples were collected, 86 from LTHU and 106 from CH. Statistically significant differences in mean bacterial load in LTHU (367 CFU/m3) and CH (230 CFU/m3) was observed, but not in mean fungal load (LTHU: 87 CFU/m3; CH: 117 CFU/m3). CH bacteria and fungi loads were statistically significantly higher in sites with outpatients or no patients compared to those with inpatients as well as in support services compared to curative care areas. No statistically significant differences were found regarding these variables in LTHU.

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