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Mark Krahmer(d)
Karen Fox(a)
Alvin Fox(a)*
Anita Saraf(b)
Lennart Larsson(b)
Airborne exposure to bacterial components found in agricultural environments can lead to pulmonary inflammation. Total (viable and nonviable) bacterial load was monitored in a stable and a dairy by a new approach, gas chromatography-tandem mass spectrometry measurement of muramic acid, a component of gram positive and gram negative bacterial peptidoglycan. Also used to assess the gram negative bacterial load were 3-hydroxy fatty acids, markers of bacterial lipopolysaccharide. Culture, an established procedure for assessing the viable bacterial portion of airborne dust, served as a basis for comparison. The muramic acid and 3-hydroxy fatty acid concentrations (total C^sub 12:0^, C^sub 14:0^, and C^sub 16:0^) showed a correlation with an R^sup 2^ of 0.81. Dust and muramic acid levels also correlated. However, although relative muramic acid levels were lower in the stable than the dairy, colony forming units (CFU) were considerably higher in the stable. The total bacterial load (estimated from muramic acid values) for both the stable and dairy was also higher than would have been predicted from culture. These results suggest that nonculture based approaches and culture provide complementary but independent measurements of airborne biopollution.
Keywords: airborne bacteria, muramic acid, 3-hydroxy fatty acids
Respiratory intake of bacteria or their substituents can lead to pulmonary irritation and inflammatory reactions associated with breathing contaminated air in the home or workplace.(1,2) This is a particular problem in agricultural settings, where the concentration of airborne matter is high and the environment serves as a fertile breeding ground for bacteria.(3 5)
Culture is by far the most widely used procedure of assessing the microbial content of airborne dust(3,6 8) and provides a quantitative measure of viable bacteria and an assessment of population diversity. For example, in recent study of a glass fiber plant, one gram negative colony type predominated, constituting the majority of the environmental biocontamination.(9) However, certain airborne pathogens (e.g., Legionella pneumophila) and other environmental opportunists are not detected using conventional media.(10) Thus, an important portion of the bacterial population may remain undetected using plate counting.
Alternative quantitative methods for assessing total (viable and nonculturable) airborne contamination are based on microscopy using fluorochromes (e.g., acridine orange) that nonspecifically stain nucleic acids.(11) Differences in numbers observed depend...