New research reveals a striking difference in indoor fungi: daycares are hotspots for yeasts, while private homes harbor more molds. Could the people inside be shaping the microbial world around us? Study: Yeasts Prefer Daycares and Molds Prefer Private Homes. Image Credit: AKIRA_PHOTO / Shutterstock A new study led by researchers from the University of Oslo, Norway, explores the distribution pattern of fungal communities across daycare centers and private houses in Norway. The findings, published in the journal Microbial Ecology, reveal a small but significant difference in fungal richness, with private houses showing higher fungal richness than outdoor samples, while daycares exhibited a similar but non-significant trend.
The study also found a higher abundance of yeast in daycares and molds in private houses. Background Almost half (49%) of the fungi found indoors were shared between daycares and homes, but 31% were unique to daycares, and 20% were unique to homes, highlighting distinct microbial environments.
Microorganisms grow at a comparatively lower rate indoors (within buildings) than outdoors due to limited humidity and nutrient insufficiency. However, some microorganisms, including molds and yeasts, can adapt to these adversities and grow at a faster rate in harsh indoor conditions.
Toxins or volatiles produced by yeasts and molds can negatively affect the immune system of the host and cause a variety of health adversities, ranging from mild superficial infections (dandruff, atopic dermatitis, or eczema, ringworm, and nail infections) to serious infections (invasive aspergillosis, mucormycosis, and candidemia). However, researchers note that the health effects of fungal composition differences between daycares and homes remain uncertain, with some studies suggesting that yeast exposure might even have a protective role against allergies and asthma in children.
Besides the fungal community (yeasts and molds) that can survive indoors, fungal spores circulating in the air can easily enter buildings through windows, doors, and ventilation systems. The influx of outdoor fungi into buildings increases during plant growth seasons when fungi are also sporulating outdoors.
To control for seasonal variation, researchers collected all dust samples throughout Norway at the same time (April–May), ensuring that climatic differences did not influence the study results.
Considering that people typically spend most of their time indoors, researchers designed this study to determine the proportions of fungal communities present in daycares and private houses in Norway. In Norway, children in daycares spend up to 70% and 31% of their time outdoors during summer and winter, respectively.
The higher density of occupants contributes significantly to the increased prevalence of yeasts, as yeasts are more commonly associated with human bodies than molds.
Researchers suggest two possible explanations for the higher abundance of yeasts in daycares: Young children may have a more diverse fungal skin microbiome compared to adults, leading to increased yeast presence in daycares. Daycares have a much higher density of occupants, which may contribute to the increased prevalence of yeasts.
In their previous study of the fungal community in two daycares, researchers found a strong seasonal pattern in the composition of the fungal community, with higher fungal richness in summer and fall. This previous research highlights the importance of considering temporal variability while analyzing indoor fungal community richness.
The study finds a clear compositional difference in the fungal community between daycares and private houses in Norway. According to the study findings, the number of occupants and their age distribution are major contributors to the observed difference in fungal composition between these building types. Researchers suggest two possible explanations for the higher abundance of yeasts in daycares: Young children may have a more diverse fungal skin microbiome compared to adults, leading to increased yeast presence in daycares.
Daycares have a much higher density of occupants, which may contribute to the increased prevalence of yeasts. However, they recommend that future studies should analyze the fungal community present in the skin and body to more conclusively identify the factors responsible for the compositional difference between these two building types.
While molds have been associated with respiratory conditions such as asthma, the study does not establish a direct health risk related to these fungal differences. Researchers suggest that further studies should assess whether exposure to different indoor fungal compositions has any impact—positive or negative—on human health.
