Application of Cytosense flow cytometer for the analysis of airborne bacteria collected by a high volume impingement sampler.

Characterization of airborne bacterial cells requires efficient collection, concentration, and analysis techniques, particularly to overcome the challenge of their dilute nature in outdoor environments. This study aims to establish a rapid and reliable approach for quantification of bacteria in air samples. To do this, a high volume impingement sampler was applied to collect airborne bacteria from a wastewater treatment plant (WWTP). The bacterial cell density was estimated by a Cytosense flow cytometer (Cytobouy) and compared to quantitative PCR (qPCR) data based on 16S rRNA genes. The average bacterial cell density measured by Cytosense ranged from 1.1 to 2.5 × 104 cells m-3 of air and that estimated by qPCR ranged from 0.08 to 3.8 × 104 cells m-3 of air. Regression analysis showed no systematic difference in bacterial cell densities between two methods applied when the cells were analyzed in vivo, and statistical tests confirmed that Cytosense counts of unfixed samples provided realistic values. Bacterial cell densities and the amount of DNA extracted from the sample were significantly correlated with relative humidity on a sampling day. The results showed that the present method was reliable to estimate bacteria densities from the outdoor environment, and the analysis given by Cytosense was faster and more sensitive than qPCR method. In addition, the Cytosense gave valuable information about cell characteristics at different sampling conditions.

Study on the initial velocity distribution of exhaled air from coughing and speaking.

Increasing concerns about the spread of airborne pathogens such as severe acute respiratory syndrome (SARS) and novel swine-origin influenza A (H1N1) have attracted public attention to bioaerosols and protection against them. The airborne pathogens are likely to be expelled from coughing or speaking, so the physical data of the exhaled particles plays a key role in analyzing the pathway of airborne viruses. The objective of this study was to analyze the initial velocity and the angle of the exhaled airflow from coughing and speaking of 17 males and 9 females using Particle Image Velocimetry (PIV) and acrylic indoor chamber. The results showed that the average initial coughing velocity was 15.3 m/s for the males and 10.6 m/s for the females, while the average initial speaking velocity was 4.07 m/s and 2.31 m/s respectively. The angle of the exhaled air from coughing was around 38° for the males and 32° for the females, while that of the exhaled air from speaking was around 49° and 78° respectively. Also, the linear relation between the tested subject's height and their coughing and speaking velocity was shown in this study.