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Methods For Counting Airborne Bacteria Inadequate, Say Researchers

Date:
August 30, 1997
Source:
American Society For Microbiology
Summary:
Current methods for detecting and counting airborne bacteria in enclosed buildings may be inadequate and understate the total number of airborne organisms, say researchers from the University of Maryland and the U.S. Environmental Protection Agency.
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     Current methods for detecting and counting airborne bacteria inenclosed buildings may be inadequate and understate the total number ofairborne organisms, say researchers from the University of Maryland andthe U.S. Environmental Protection Agency in the September 1997 issueof the journal Applied and Environmental Microbiology.

     Indoor air pollution has become a serious concern.  Newer, energyefficient buildings are usually sealed, recycling the air and increasing thenumber of bacteria in the environment.  An estimated 10 to 25 millionworkers in the United States show symptoms of "sick buildingsyndrome" (SBS) annually.  The role of airborne bacteria in SBS is stilllargely unknown but it is generally accepted that microorganisms areinvolved.

     In the study the researchers tested the effects of aerosolization onviability and colony-forming ability on several bacterial species.  Thebacteria were sprayed into glass containers and then total numbers werecounted by two different methods.  The first method was the methodtraditionally employed to determine indoor air quality where the thebacteria are cultured and the colonies formed are counted.  The other wasdirect staining and counting of viable bacteria.   The researchers foundthat less than 10 percent of the aerosolized bacteria were capable offorming colonies.

     "From these results it is concluded that the bacterial strains includedin this study did not respond to standard culture methods afteraerosolization," say the researchers.  "The plate [colony] count providesan estimate of only those few cells least affected by exposure to air."  (J.F. Heidelberg, M. Shahamat, M. Levin, I. Rahman, G. Stelma, C.Grim, and R.R. Colwell.  1997.  Effect of aerosolization onculturability and viability of gram-negative bacteria.  Applied andEnvironmental Microbiology 63:3585-3588.)


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American Society For Microbiology. "Methods For Counting Airborne Bacteria Inadequate, Say Researchers." ScienceDaily. ScienceDaily, 30 August 1997. <www.sciencedaily.com/releases/1997/08/970830062324.htm>.
American Society For Microbiology. (1997, August 30). Methods For Counting Airborne Bacteria Inadequate, Say Researchers. ScienceDaily. Retrieved August 1, 2015 from www.sciencedaily.com/releases/1997/08/970830062324.htm
American Society For Microbiology. "Methods For Counting Airborne Bacteria Inadequate, Say Researchers." ScienceDaily. www.sciencedaily.com/releases/1997/08/970830062324.htm (accessed August 1, 2015).

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