THE Resistance of two strains of bacterium coli type i to drying under atmospheric conditions
1955
Garvie, Ellen I.
SUMMARY: Suspensions of two strains of Bacterium coli type I were dried as thin films under atmospheric conditions and the numbers of organisms determined before and after drying. Three methods were used to grow the culture; in two the culture was grown in broth and in the other on agar slopes. Strain 28.D.10 was less sensitive than strain NCTC 5934. After culturing in broth NCTC 5934 showed irregular daily fluctuations in sensitivity to drying; 28.D.10 became more sensitive for the first 2-3 weeks and thereafter less sensitive. Suspensions prepared from 18 hr plate cultures were more sensitive than from 24 hr plate cultures; a change from peptone water to Lemco broth for daily culturing slightly decreased the sensitivity to drying. With both strains suspensions prepared from broth cultures were more sensitive than those from agar slopes. Continuous daily culturing of 28.D.10 on a solid medium as compared with broth decreased the sensitivity of suspensions and over a long period the culture appeared to be more stable. When strain NCTC 5934 was grown on a solid medium the suspension was as sensitive to drying as that obtained when broth was used but the daily fluctuation of results appeared to be less. A decrease in the number of cells in the 24 hr broth culture of 28.D.10 coincided in time with an increase in the sensitivity to drying of the suspension prepared from the same culture.
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