Use of gelatin filter and BioSampler in detecting airborne H5N1 nucleotides, bacteria and allergens

In this study, the pure influenza A virus (H5N1) nucleotides, dermatophagoides allergens (Der f 1 and Der p 1), and Bacillus subtilis vegetative cells were aerosolized and collected by a Button Aerosol Sampler equipped with gelatin filter and a BioSampler, which were operated at 4 and 12.5 L/min, respectively, for 1–5 min. The collected air samples were analyzed by quantitative polymerase chain reaction (qPCR) and enzyme-linked immuosorbent assay (ELISA). In addition, the performances of the samplers when quantifying total outdoor bacteria were also studied.The cycle threshold (Ct) value for 0.1 fg/μl RNA positive control was observed around 26, and the Ct value for the negative control was about 30. Gelatin filters were shown to report 1-2 times higher nucleotides and B. subtilis concentrations than those obtained by the BioSampler. When sampling outdoor bacteria, both samplers however obtained similar concentration levels (p-value=0.36). In contrast, the BioSampler reported substantially higher dust mite allergen concentration levels, especially for Der f 1 than the gelatin filters in this study. The sampling time up to 5 min was shown not to have a statistically significant effect on the performance of qPCR when the gelatin filter was used. Such finding was also observed with the performance of ELISA for the sampling time up to 15 min.This study suggests that the bioaerosol sampler, collection medium and analysis methods such as qPCR and ELISA would play overall roles in characterizing airborne biological materials.