On Certain Factors Influencing the Survival of Bacteria in Water and in Saline Solutions

Abstract

Various bacterial emulsions remained viable for 5-32 mo. in 0.85% NaCl at various temp., and 14-32 mo. in distilled water. The bacterial concentration required for survival of B. typhosus in emulsion in distilled water or in 0.85% NaCl for a given time at a given temp. can be approximately determined. This varies greatly with temp. and emulsifying fluid employed. Distilled water is a more favorable medium for survival than 0.85% NaCl for B. typhosus, B. coli, B. tuberculosis, B. diphtheriae, Strep. hemolyticus, Strep. viridans, etc. Prolonged survival of B. typhosus in distilled water and in 0.85% NaCl is associated with a late period of comparatively low death rate. In B. typhosus at 37[degree] C, onset of a period of low death rate may be detected after about 3 weeks. The fact that B. typhosus in distilled water survives so much longer at room temp. than at 37[degree] C. points to low temp. as a factor of considerable importance in production of winter river typhoid in temperate climates. Washing B. typhosus, either in 0.85% NaCl, or in distilled water, shortens its survival period when resuspended in these fluids. The supernatant fluid removed in washing prolongs the survival period of the relatively few bacteria inevitably present. Great dilution of an emulsion of bacteria appears to be almost equivalent to washing in its effect. 10-20% plain nutrient broth diluted with 0.85% NaCl is the optimum concentration for prolonged survival of B. typhosus at 37[degree]; 0.1% is sufficient definitely to prolong survival. 0.85% NaCl appears to be toxic to certain organisms when stored in nutrient media at 37[degree]. Reduction in concentration of NaCl in culture media might assist in preservation of cultures of certain delicate organisms. Room temp. appears to be more favorable for survival of most organisms in distilled water and in 0.85% NaCl than 0[degree]-8[degree]. Streptococci and B. diphtheriae are exceptions. Duration of survival of several of the Gram-negative bacilli appears to be more uniformly long in distilled water and in NaCl solutions than on solid media.