Non-Seasonal Variation of Airborne Aspergillus Spore Concentration in a Hospital Building.

Michael Oberle,Thomas Bregenzer,Reto Laffer,Hans Fankhauser,Cornelia Ottiger,Markus Reichmuth

doi:10.3390/ijerph121113730

Abstract

Nosocomial fungal infections are gaining increased attention from infectiologists. An adequate investigation into the levels of airborne Aspergillus and other fungal spores in hospital settings, under normal conditions, is largely unknown. We monitored airborne spore contamination in a Swiss hospital building in order to establish a seasonally-dependent base-line level. Air was sampled using an impaction technique, twice weekly, at six different locations over one year. Specimens were seeded in duplicate on Sabouraud agar plates. Grown colonies were identified to genus levels. The airborne Aspergillus spore concentration was constantly low throughout the whole year, at a median level of 2 spores/m3 (inter-quartile range = IQR 1–4), and displayed no seasonal dependency. The median concentration of other fungal spores was higher and showed a distinct seasonal variability with the ambient temperature change during the different seasons: 82 spores/m3 (IQR 26–126) in summer and 9 spores/m3 (IQR 6–15) in winter. The spore concentration varied considerably between the six sampling sites in the building (10 to 26 spores/m3). This variability may explain the variability of study results in the literature.

Highlights

Data on the frequency and distribution of Aspergillus and other fungal spores in hospital buildings, under normal conditions, are insufficient to lead to meaningful conclusions [1,2]
Aspergillus spores showed no seasonal variation between winter and summer
Seventy-seven percent of all Aspergillus spp. grew at 36 ± 1 °C of which more than 95% were identified as A. fumigatus

Summary

Introduction

Data on the frequency and distribution of Aspergillus and other fungal spores in hospital buildings, under normal conditions, are insufficient to lead to meaningful conclusions [1,2]. Samplings of airborne spores are often done under specific conditions, such as an increased rate of invasive aspergillosis (IA), to identify the sources or reasons for the contamination. To better estimate the situation under investigation, an in-house spore concentration base-line is necessary for comparison with buildings with mould related problems. Inhaled spores of Aspergillus, otherwise considered harmless to an immune competent individual, can cause life threatening invasive fungal infections in immune-suppressed patients, such as haematooncological patients or in patients after solid organ transplantation. Management of fungal infections is challenging, treatments are expensive, and morbidity and mortality rates are high [3,4]. The accommodation of highly susceptible patients in HEPA air-filtered units is, an internationally accepted preventive measure [5,6]

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Discussion

Conclusion