Abstract
Objective: This study analyzed how effectively bacteria penetrate through a new filtering device (Muski™) aimed at providing temporary protection against hazardous air contaminants. Materials and methods: A 1.5–7×108 cfu/ml bacterial or spore suspension was aerosolized. Fragments of the Muski filter, previously sterilized by gamma rays, were placed in a sterile stainless steel Seitz filter holder, plugged into an Erlenmeyer vacuum flask connected to a vacuum pump to force the bacteria aerosol through the Muski filter. As a control the same apparatus was used without the Muski filter. To evaluate the bacteria passing through the apparatus, diluent solution was introduced in the Erlenmeyer flask, which was then subjected to mechanical shaking. Both the contents of Erlenmeyer flask and the diluent solution, used to rinse out the Erlenmeyer flask, were filtered through a membrane filtration apparatus. The filtration membrane was transferred to the surface of a Petri dish containing a suitable culture medium for the species of bacteria tested. After incubation the number of developed cfu (colony forming units) was evaluated. Results: The presence of the Muski filter in the experimental aspiration apparatus strongly reduced the passage of bacteria and spores of varying shapes and sizes that were experimentally dispersed into the air. The logarithmic reduction varied from 1.77 to 3.90 for the vegetative forms and from 1.24 to 2.05 for bacillus spores. Conclusion: The results demonstrate that the Muski device is a valid alternative to traditional respirators, including those of the last generation. Nevertheless, the Muski device must be considered as a ‘first aid’ device, to be carried by the person to permit a safe, rapid escape from the area presumed to be contaminated by bacteria.