TECHNIQUES FOR DISPERSION OF MICROORGANISMS INTO AIR

Many commercially available devices initially developed for dispersion of biologically inert particles have been adopted for aerosolization of microoganisms in laboratory settings. However, these dispersion dev ices are not always adequate for microbial particles, as they do not s imulate natural release into air. Wet dispersion methods are appropria te for viruses and most bacteria, whereas dry methods are more suitabl e for most fungal and actinomycete spores. Characteristics of the resu lting aerosol are dependent on the dispersing shear forces and the sen sitivity and agglomeration of the tested microorganisms. Consequently, each microbial group may need a specific dispersion technique. The fo llowing devices have been developed and tested in this study: the bubb ling aerosol disperser, the agar-tube disperser, and the swirling-how disperser. Testing included the evaluation of both physical and microb iological characteristics of aerosolized microorganisms. Each of the d ispersers has shown several advantages over commercially available one s. When used for the dispersion of bacteria from the liquid suspension , the bubbling aerosol disperser was found to produce considerably few er amounts of microbial fragments and much lower levels of microbial m etabolic injury than the commercially available Collison nebulizer. Fu ngal spores dispersed from their colonies by the agar-tube disperser w ere found to have a more stable aerosol concentration and a lower frac tion of agglomerates than achievable by conventional powder dispersion . The swirling-flaw dispersion technique was used far aerosolization o f actinomycetes because the agar-tube disperser could not provide a st able concentration of these spores due to their smaller size. The test s have shown that new methods minimize the changes of properties of th e microorganisms during their aerosolization in the laboratory. (C) 19 97 American Association for Aerosol Research.