Modelling the combined temperature and salt (NaCl) limits for growth of a pathogenic Escherichia coli strain using nonlinear logistic regression.
A broth-based method is used to determine if exponential phase Escherichia coli R31, an STEC, is able to grow within 50 days under various combinations of sub-optimal temperatures and salt concentrations. From these data, the growth limits for combinations of temperature (7.7-37.0 degrees C) and water activity (0.943-0.987; NaCl as humectant) are defined and modelled using a nonlinear logistic regression model. That form of model is able to predict the combinations of salt concentration/water activity and temperature that will prevent the growth of E. coli R31 with selected levels of confidence. The model fitted the data with an approximate concordance rate of 97.3%. The minimum water activity that permitted growth occurred in the range 25-30 degrees C, the temperature range which optimises cell yield. At temperatures below this range the minimum water activity which allowed growth increased with decreasing temperature.
Salter
M A
MA
School of Agricultural Science, University of Tasmania, Hobart, Australia.
Ratkowsky
D A
DA
Ross
T
T
McMeekin
T A
TA
D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development*; D016015:Logistic Models; D008954:Models, Biological; D017711:Nonlinear Dynamics; D012965:Sodium Chloride / Q000494:pharmacology*; D013696:Temperature; D014867:Water
D003470:Culture Media; D014867:Water; D012965:Sodium Chloride