Potential Respiratory Deposition and Species Composition of Airborne Culturable, Viable, and Non-Viable Fungi during Occupancy in a Pig Farm

Abstract

Fungal species composition and site of deposition within the airways affects whether diseases develop and where they may arise. The aim of this study is to obtain knowledge regarding the potential deposition of airborne culturable, viable, and non-viable fungi in the airways of pig farm workers, and how this composition changes over multiple sampling days. Airborne fungi were sampled using impactors and subsequently analyzed using amplicon sequencing and matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) fingerprinting. The geometric mean aerodynamic diameter (Dg) of airborne particles with culturable airborne fungi were not affected by sampling days and ranged in size between 3.7 and 4.6 µm. Amplicon sequencing of the internal transcribed spacer region of the rRNA gene operon, in combination with DNA interchelating agents, revealed a large presence of non-viable fungi, but several pathogenic and toxic fungal species were detected in the viable portion. The diversity was found to be significantly associated with the sampling day but did not change significantly over multiple sampling rounds during the same day. The non-viable fraction contained genera typically associated with the pig gastrointestinal tract, such as Kazachstania and Vishniacozyma. In conclusion, the Dg of culturable fungi was between 3.7 and 4.6 µm, and the Dg of the viable and total fungi was 1.5 and 2.1 µm, respectively. The species composition changed over the multiple sampling days.

Antifungal Resistance in Isolates of Aspergillus from a Pig Farm

“…In this study, the sampled material with the greatest number of Aspergillus isolates was the straw, which was also the only sampled material from which A. niger was identified. Other studies have found A. niger in airborne dust particles from pig farms [16,22]. However, this study was performed sampling a smaller volume of air than the other studies, and it is therefore possible that airborne spores or hyphal fragments of A. niger were present in the pig farm, but were simply not collected in our samples.…”

“…Of the research done regarding occupational exposure to fungi, most has focused on potential respiratory deposition [16], microbial community composition [33,40], or mycotoxin contents [41]. While all of these aspects are important with regards to the development of an accurate occupational risk assessment, they do not consider antifungal resistance.…”

“…Previous research on the indoor air in pig farms has shown that workers are potentially exposed to high concentrations of airborne fungi during their work [15]. Many of the species they are exposed to are known to be pathogenic or toxin producers, and exhibit the potential to deposit deep within the airways [16]. Although workers are unlikely to develop an occupationally derived fungal lung infections-likely due to the so-called "healthy worker effect"-they are at an increased risk of developing a serious infection if they become susceptible [17].…”

“…The genus Aspergillus is of particular interest, as it contains several species known to be human pathogens [21] and that are known to be present in pig farms [16,22]. In particular, the species Aspergillus niger has been found on surfaces, such as soil and leaf surfaces, in occupational settings such as greenhouses [23,24].…”

Particulate Matter in Swine Barns: A Comprehensive Review

“…This, consistent with early findings (Carpenter, 1986), suggests that the bacteria may not exist as individual particles but bind to large particles in the air. Comparatively, culturable fungal counts peaked at approximately 2-5 µm (Sowiak et al, 2012;White et al 2020), suggesting that airborne fungi in swine barns may exist as individual spores/particles. Different size distribution patterns suggest that airborne bacteria and fungi may undergo different aerodynamic transport and removal processes in swine barns (Zhang, 2005) and different strategies may be required for the mitigation of airborne bacteria than fungi.…”