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Research article

Airborne bacterial species in indoor air and association with physical factors

Authors
  • Anne Mette Madsen orcid logo (National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark)
  • Saloomeh Moslehi-Jenabian (National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark)
  • Mika Frankel (National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark)
  • John Kerr White orcid logo (National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark)
  • Margit W. Frederiksen orcid logo (National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark)

This is version 2 of this article, the published version can be found at: https://doi.org/10.14324/111.444/ucloe.000056

Abstract

The aim of this study is to obtain knowledge about which cultivable bacterial species are present in indoor air in homes, and whether the concentration and diversity of airborne bacteria are associated with different factors. Measurements have been performed for one whole year inside different rooms in five homes and once in 52 homes. Within homes, a room-to-room variation for concentrations of airborne bacteria was found, but an overlap in bacterial species was found across rooms. Eleven species were found very commonly and included: Acinetobacter lowffii, Bacillus megaterium, B. pumilus, Kocuria carniphila, K. palustris, K. rhizophila, Micrococcus flavus, M. luteus, Moraxella osloensis and Paracoccus yeei. The concentrations of Gram-negative bacteria in general and the species P. yeei were significantly associated with the season with the highest concentrations in spring. The concentrations of P. yeei, K. rhizophila and B. pumilus were associated positively with relative humidity (RH), and concentrations of K. rhizophila were associated negatively with temperature and air change rate (ACR). Micrococcus flavus concentrations were associated negatively with ACR. Overall, this study identified species which are commonly present in indoor air in homes, and that the concentrations of some species were associated with the factors: season, ACR and RH.

Keywords: Bacillus megaterium, bacteria, exposure, home environment, indoor air, indoor humidity, MALDI-TOF MS, Paracoccus yeei, room-to-room variation, seasonality

Rights: © 2023 The Authors.

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Published on
30 Mar 2023
Peer Reviewed
License
Creative Commons Attribution 4.0

 Open peer review from Hector Altamirano

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-LIFE.AW03NY.v1.REJTZX
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Life sciences
Keywords: Paracoccus yeei , exposure , indoor air , indoor humidity , Built environment , bacteria , MALDI-TOF MS , Bacillus megaterium , Health , seasonality , room-to-room variation , home environment

Review text

Very interesting study. This paper describes the bacterial species found in Danish homes and their link with environmental factors. The methodology used to collect bacterial species is very clear and well-described. However, further information regarding the various studies mentioned, the monitoring of environmental conditions and calculation methods should also be provided in detail. Specific comments below:

  1. On the background page, the author mentioned emerging human pathogens; Are there any of the species found in the study considered critical pathogens to be concerned about? Also, please describe within the paper the term ‘species composition.
  2. Please specify or discuss the likely sources of the species found.
  3. Provide details of the three studies mentioned in the Study design section. The author mentioned Study A, B and C.
  4. Clarify whether the bacterial species reported in the document were collected in 52 homes and five extra homes or if the five homes are part of the 52.
  5. Were RH and ACH recorded in all 52 homes or just five?
  6. Describe in detail how relative humidity and temperature were monitored and recorded in each study (A, B, C). Please also report on the period recorded (season, yearly, daily, etc.), intervals, locations of sensors within each room, external conditions, constant or one-off measurement (one per season), etc.
  7. Were temperature and relative humidity recorded simultaneously as sampling bacterial species?
  8. Please provide details about how Air Change Rate was calculated and the period it refers to.
  9. It would also be good to present a summary of the environmental conditions (e.g. RH and temperature levels) recorded and analysed within the documents. In the document, the author indicated that bacteria concentration was affected by low ACH or when RH was highest. However, how high is the highest? What levels of RH are you referring to? Furthermore, for how long they remain high.



Note:
This review refers to round 1 of peer review.

 Open peer review from Spyros Efthymiopoulos

Review

Review information

DOI:: 10.14293/S2199-1006.1.SOR-LIFE.ACX6EG.v1.RMQHYS
License:
This work has been published open access under Creative Commons Attribution License CC BY 4.0 , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com .

ScienceOpen disciplines: Life sciences
Keywords: Paracoccus yeei , exposure , indoor air , indoor humidity , Built environment , bacteria , MALDI-TOF MS , Bacillus megaterium , Health , seasonality , room-to-room variation , home environment

Review text

A fascinating piece of work! The assessment of indoor bacterial growth has been rarely done using air sampling, which makes this study highly valuable.

A few minor comments that could help readers better understand the context of this study.

  1. Was the environmental setting (i.e., RH, Temperature, activities carried out by occupants, the opening of windows, level of cleanliness) monitored prior to sampling? Could some of the indoor environmental conditions have affected the results reported?
  2. Were the results from the living rooms of the 5 homes tested for studies A and B included in study C? If not, would it be of value to add the results of the 5 living rooms to the 52 samples?
  3. Could you please mention how many of the 52 living rooms in study C were tested during each season? This would allow readers to see the distribution of samples in each season.
  4. Could you please briefly mention the methods used to monitor the RH, T, ACH in the studies you cited (12, 17, 21)?
  5. Please insert the axis title in figure 1
  6. It would be very helpful if we could also see the composition of bacteria with different seasons. This would help the readers to visualize the potential changes in the concentration of the most dominant species with seasons.
  7. Would it be possible to report some key features like the temperatures, RH, and ACH measurements for the tested properties? These would help readers to understand better the relationship between the environmental context and the bacterial readings.



Note:
This review refers to round 1 of peer review.