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In this study total concentration, viability, culturability of indoor and outdoor bioaerosols in ten residential environments were studied by using a cultivating method and an epifluorescence microscopy method with fluorochrome (EFM/FL) using four different dyes (AO, DAPI, PI, and YOPRO-1). Results from the EFM/FL were then compared with those from the traditional cultivating method. The total indoor microbial cell concentrations measured by EFM/FL was 630 to 5200 times higher than that measured by the cultivating method; ranging from 1.38 × 106 to 4.48 × 106cells/m3 (microbial cells per cubic meter) with AO staining, and from 7.84 × 105 to 2.75 × 106 cells/m3 with DAPI staining, compared with the average concentration of 721 CFU/m3 for bacteria and 587 CFU/m3 for fungi by the cultivating methods. The viability of bioaerosols ranged from 0.63 to 0.92 by EFM/FL with PI staining, from 0.19 to 0.72 by EFM/FL with YOPRO-1 staining, and from 0.0002 to 0.0015 by the cultivating method. The viability determined by EFM/FL was much higher than the culturability. In summary, the total microbial cell concentration and viability were highly underestimated by the cultivating method. In conclusion, EFM/FL method can effectively assess the total concentration and viability of bioaerosols in indoor samples.
Acknowledgments
This work was partially supported by grant NSC 93-2320-B002-003 from the National Science Council, Republic of China.
Notes
a significantly different from YOPRO-1 (p < 0.001).
