Experimental Technique for Studying Aerosols of Lyophilized Bacteria

Abstract

An experimental technique is presented for studying aerosols generated from lyophilized bacteria by using Escherichia coli B, Bacillus subtilis var. niger, Enterobacter aerogenes, and Pasteurella tularensis. An aerosol generator capable of creating fine particle aerosols of small quantities (10 mg) of lyophilized powder under controlled conditions of exposure to the atmosphere is described. The physical properties of the aerosols are investigated as to the distribution of number of aerosol particles with particle size as well as to the distribution of number of bacteria with particle size. Biologically unstable vegetative cells were quantitated physically by using 14C and Europium chelate stain as tracers, whereas the stable heat-shocked B. subtilis spores were assayed biologically. The physical persistence of the lyophilized B. subtilis aerosol is investigated as a function of size of spore-containing particles. The experimental result that physical persistence of the aerosol in a closed aerosol chamber increases as particle size is decreased is satisfactorily explained on the bases of electrostatic, gravitational, inertial, and diffusion forces operating to remove particles from the particular aerosol system. The net effect of these various forces is to provide, after a short time interval in the system (about 2 min), an aerosol of fine particles with enhanced physical stability. The dependence of physical stability of the aerosol on the species of organism and the nature of the suspending medium for lyophilization is indicated. Also, limitations and general applicability of both the technique and results are discussed.

Aerosol Survival of Pasteurella tularensis Disseminated from the Wet and Dry States

“…tracers for physical decay (1). Unlike the situation with E. coli B or Enterobacter aerogenes ATCC 13048, both tracers were found to be suitable (13). The results given are all with the spore tracer.…”

“…Most of these details have been published by Cox (4,7,11,13); additional detail is given below. The growth medium for P. tularensis live vaccine strain (LVS) was, per 100 ml of distilled water, 2 g of NZ amine A (Sheffield Chemical Co.), 0.5 g of Basamin Busch yeast product, 0.5 g of NaCl, 1 ml of stock thiamine solution (0.01%), and 1 ml of stock KxHyPO4 solution (22.5% K2HP04, 5.3% KH2PO4).…”

Aerosol Survival of Pasteurella tularensis and the Influence of Relative Humidity

“…Liquid cultures were disseminated with a Wells atomizer (24). Freeze-dried powders were disseminated pneumatically as previously described (10,11,13). Aerosols were stored in air in a facility incorporating eight rotating drums (15) maintained at 26.8 C. Aerosols were usually sampled directly onto agar with the syringe-slit sampler technique (15).…”

Aerosol Survival of Pasteurella tularensis and the Influence of Relative Humidity

“…Liquid cultures were disseminated with a Wells atomizer (24). Freeze-dried powders were disseminated pneumatically as previously described (10,11,13). Aerosols were stored in air in a facility incorporating eight rotating drums (15) maintained at 26.8 C. Aerosols were usually sampled directly onto agar with the syringe-slit sampler technique (15).…”