Examination of the Thermal Resistance of Enterococcus Faecalis and Escherichia Coll and the Possibility of Heat Resistance Transfer

Location

CSU

Student's Major

Biological Sciences

Student's College

Science, Engineering and Technology

Mentor's Name

Dorothy Wrigley

Mentor's Department

Biological Sciences

Mentor's College

Science, Engineering and Technology

Description

Pasteurization is the use of low heat to kill bacteria in foods. Because bacteria rarely exist as pure cultures in nature, it is feasible that a thermo-tolerant organism might affect the survival of a less thermally tolerant organism, thus limiting the effectiveness of pasteurization. This study examines the effect of heat-resistant Enterococcus faecalis on heat-sensitive Escherichia coli. Preliminary tests determined the appropriate media for counting the surviving organisms in the mixed cultures. Then, the thermal resistance of E.coli and E.faecalis was measured by D-values and compared for single and mixed cultures. When the two bacteria were mixed and heated, no change in D-value was seen for E.coli. However, when the mixture was cultured for 2.5 hours prior to heating, the number of surviving E.coli increased. This leads to the preliminary conclusion that E.faecalis has a positive effect on the survival of E.coli.

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Examination of the Thermal Resistance of Enterococcus Faecalis and Escherichia Coll and the Possibility of Heat Resistance Transfer

CSU

Pasteurization is the use of low heat to kill bacteria in foods. Because bacteria rarely exist as pure cultures in nature, it is feasible that a thermo-tolerant organism might affect the survival of a less thermally tolerant organism, thus limiting the effectiveness of pasteurization. This study examines the effect of heat-resistant Enterococcus faecalis on heat-sensitive Escherichia coli. Preliminary tests determined the appropriate media for counting the surviving organisms in the mixed cultures. Then, the thermal resistance of E.coli and E.faecalis was measured by D-values and compared for single and mixed cultures. When the two bacteria were mixed and heated, no change in D-value was seen for E.coli. However, when the mixture was cultured for 2.5 hours prior to heating, the number of surviving E.coli increased. This leads to the preliminary conclusion that E.faecalis has a positive effect on the survival of E.coli.