Preservation of Bacteria by Circulating-Gas Freeze Drying

Abstract

Water-washed Serratia marcescens and Escherichia coli were freeze dried in a circulating-gas system at atmospheric pressure. This convective procedure resulted in a substantially higher survival of organisms than could be obtained by the vacuum method of freeze drying. There was little or no decrease in cell viability during convective drying when the residual moisture content was 15 %o or higher. Below this level, survival declined with decreasing moisture content. A detailed comparison of the convective and vacuum methods indicated that the advantage gained by freeze drying bacteria in air accrues in the early period of sublimation, at which time cells were found to be sensitive to vacuum drying but insensitive to air drying. An explanation for this difference is proposed, based upon the kinetics of water removal in the two processes. In brief, it is suggested that the convective method permits samples to be dried more uniformly; and regional over-drying, which may be deleterious even if transient, is thus avoided in achieving the optimal level of moisture.

ChromID® CARBA Agar Fails to Detect Carbapenem-Resistant Enterobacteriaceae With Slightly Reduced Susceptibility to Carbapenems

“…Limited detection of CPE might be also attributable to a loss of the resistance-harboring plasmids during lyophilization (Wagman and Weneck, 1963;Berman et al, 1968;Wein et al, 2019). We can exclude this as an important factor in our study because we observed similar bacterial titers on selective and non-selective in-house media (data not shown).…”

Physical and chemical stresses of aerosolization

“…enon. Wagman (23), however, demonstrated a marked dependence of survival upon residual moisture in studies of circulating-gas (air) freezedrying of water-washed S. marcescens and E.…”