Influence of Time and Temperature of Incubation on Heat Resistance of Escherichia coli

Abstract

Field and laboratory observations (Frazier et al. 1935) long have indicated that the temperature of incubation of Swiss cheese starter cultures significantly influences their ability to develop following the rather severe heat exposure to which they are subjected during manufacture. If it were true that the temperature of growth had an effect on heat resistance of bacteria, this fact would be of significance in various fermentations, both commercial and natural, and would prove of general interest from the standpoint of the physiology of bacteria. Therefore, an investigation was initiated to determine the influence of incubation temperature and time on the thermal resistance of certain Swiss cheese starter cultures. For the purpose of comparison, similar studies were undertaken with a typical strain (H-52) of Escherichia coli. The results of the investigations on E. coli are presented in this paper. Because it produced less acid, was able to develop under a wider variety of environmental conditions, and could be counted fairly accurately by the plate method, E. coli gave results which were more conclusive than those obtained with the lactic starter cultures and indicated that E. coli, a favorite subject for experimentation, is an ideal organism for studies on the heat resistance of vegetative cells. Despite the apparent importance of the relationship between the growth temperature and thermal resistance of bacterial cells, iThis work has been aided by a grant from the Wisconsin Alumni Research Foundation.

Thermoduric Organisms in Milk. Part I. A Review of the Literature

“…This aspect is closely bound up with the above observations and the observations of Elliker & Frazier (1938) on ' physiological youth ' (following Sherman & Albus, 1923) gave a reason for Eijkman's inverted S curve. These authors stated that cells exhibit a relatively high degree of heat resistance during the early or stationary phase of growth followed by a decline in resistance as soon as active reproduction begins, with an increase again as growth slows down and the density of the population is at its maximum with the majority of cells physiologically older.…”

“…In general, organisms are most resistant when grown a t their optimum temperature. This statement was made by Elliker & Frazier (1938) as a result of cultivating organisms a t 28" and 38.5" and should not be confused with storage of organisms at temperatures below the reasonable limit for growth, as we have observed that bacteria are more resistant when they are not actively proliferating. It is possible that organisms grown a t temperatures other than their optimum tend to become damaged in the same manner as if grown in the presence of small amounts of disinfectant.…”

Thermal inactivation of Enterococcus faecium: effect of growth temperature and physiological state of microbial cells

“…This lack of conformity may perhaps be due to species and strain differences or differences in methodology, although it is possible that acquired thermoresistance can be influenced by other factors. It has been pointed out that the incubation temperature influences the degree of increase in the heat resistance during the bacterial growth (Elliker and Frazier 1938) but, as far as we know, no further studies have been made to clarify this finding. In the particular case of Ent.…”

TEMPERATURE SHIFT EFFECTS ON INJURY AND DEATH IN LISTERIA MONOCYTOGENES SCOTT A

“…A number of microorganisms have been shown to produce heat sensitive cells when grown at low temperatures (Elliker and Frazier 1938;White 1953;Ng et al 1969;Dega et al 1972;Beuchat and Worthington 1976). A few studies have been done demonstrating that shift-up of cells grown at a lower temperature to a higher incubation temperature results in microorganisms that are more heat resistant.…”