title: The occupant as a source of house dust bacteria.
abstract: BACKGROUND
  Markers for microbial groups are commonly measured in house dust samples to assess indoor exposure to microbes in studies on asthma and allergy. However, little is known about the sources of different microbes. A better understanding of the nature and origin of microbes present in the immediate environment of human beings is crucial if one wants to elucidate protective as well as adverse effects on human health.
  
  
  OBJECTIVE
  To determine the extent to which the bacterial composition of mattress and floor dust reflects the presence of the human body in relation to other environmental sources.
  
  
  METHODS
  House dust and skin surface swab samples of occupants in 4 homes were collected and analyzed for their bacterial content, using a culture-independent methodology. Bacterial sequences analyzed from the different house dusts and skin surface swabs represented random samples of bacteria present in a given sample. Highly similar sequences were grouped to assess biodiversity and to draw conclusions about the sources of bacteria.
  
  
  RESULTS
  The bacterial flora in the house dust samples was found to be highly diverse and dominated by gram-positive bacteria. To a considerable extent, the presence of different bacterial groups was attributed to human sources. In the individuals' mattress dust samples, 69% to 88% of the bacterial sequences analyzed were associated with human origins. The respective percentages for the individual floor dusts ranged from 45% to 55%.
  
  
  CONCLUSIONS
  Our study indicates that human-derived bacteria account for a large part of the mainly gram-positive bacterial content in house dust.
authors.affiliation: Department of Environmental Health, National Institute for Health and Welfare, Kuopio, Finland. martin.taubel@thl.fi
authors.forename: Martin
authors.initials: M
authors.lastname: Täubel
authors.forename: Helena
authors.initials: H
authors.lastname: Rintala
authors.forename: Miia
authors.initials: M
authors.lastname: Pitkäranta
authors.forename: Lars
authors.initials: L
authors.lastname: Paulin
authors.forename: Sirpa
authors.initials: S
authors.lastname: Laitinen
authors.forename: Juha
authors.initials: J
authors.lastname: Pekkanen
authors.forename: Anne
authors.initials: A
authors.lastname: Hyvärinen
authors.forename: Aino
authors.initials: A
authors.lastname: Nevalainen
mesh_terms: D001249:Asthma / Q000382:microbiology*; D001512:Bedding and Linens / Q000382:microbiology; D015415:Biomarkers / Q000032:analysis; D004269:DNA, Bacterial / Q000032:analysis; D004391:Dust / Q000032:analysis / Q000276:immunology*; D004781:Environmental Exposure / Q000032:analysis; D004784:Environmental Monitoring; D005260:Female; D005430:Floors and Floorcoverings; D006094:Gram-Positive Bacteria / Q000145:classification / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D006967:Hypersensitivity / Q000382:microbiology*; D008297:Male; D012867:Skin / Q000276:immunology / Q000382:microbiology*
chemical_list: D015415:Biomarkers; D004269:DNA, Bacterial; D004391:Dust