Transmission characteristics of respiratory droplets aerosol in indoor environment: an experimental study.

Transmission of droplets has been recognized as an important form of infection for the respiratory diseases. This study investigated the distribution of human respiratory droplets and assessed the effects of air change rate and generated velocity on droplet transmission using an active agent in an enclosed chamber (46 m3). Results revealed that the higher the air change rate was, the fewer viable droplets were detected in the range of <3.3 µm with ventilation; an increased air change rate can increase the attenuation of droplet aerosol. Without ventilation, the viable droplet size was observed to mainly distribute greater than 3.3 µm, which occupied up 87.5% of the total number. When the generated velocity was increased to 20 m/s, 29.38% of the viable droplets were detected at the position of 2.0 m. The findings are excepted to be useful for developing the technology of reducing droplet propagation and providing data verification for simulation research.

Interaction between ß-lactam antibiotic and phosphorus-accumulating organisms.

ß-Lactam antibiotics have been widely used in clinic due to strong antibacterial activity with mild adverse side effects and have been detected in the environment. In the enhanced biological phosphorus removal (EBPR) process, phosphorus-accumulating organisms (PAOs) play a major role. In this study, amoxicillin, aztreonam, and cefoperazone are the selected antibiotics that applied in investigating the interaction mechanism of ß-lactam antibiotics and PAO. The effects of ß-lactam antibiotics on PAOs were analyzed comprehensively from the aspects of antibiotic impacts on phosphorus removal rate, intracellular polymer, their toxicity to PAOs, and PAO impacts on the fate of ß-lactam antibiotics. It was found that the phosphorus removal rate of PAO increased by 19.21% and 15.75%, respectively at 10 mg/L amoxicillin and aztreonam, while cefoperazone had certain inhibition effect on phosphorus removal efficiency. Quantitative analysis shows that in the aerobic stage, three kinds of ß-lactam antibiotics could promote the synthesis of polyphosphates (poly-P). The degradation rates of three antibiotics were as follows: amoxicillin > aztreonam > cefoperazone. The fate characteristics of antibiotics provide a theoretical basis for environmental risk assessment. The toxic effects of three antibiotics were as follows: cefoperazone > aztreonam > amoxicillin according to the bacteriostatic test. It provided a scientific theoretical basis for systematically evaluating the biological toxicity of antibiotic pollutants.