Predicting microbial growth: graphical methods for comparing models.

Some simple computer-based graphics were used to compare different models predicting microbial growth responses of salmonellae to three factors (pH, sodium chloride concentration and incubation temperature). Simple linear regression, contour and three-dimensional surface plots all revealed gross differences between the predicted growth parameters from different growth models. Regression and contour plots were found to be more sensitive to small differences in surface topography, but three-dimensional surface plots provided a good overview.

Differentiation of Staphylococcus aureus from freshly slaughtered poultry and strains 'endemic' to processing plants by biochemical and physiological tests.

A comparison was made of 27 'endemic' strains of Staphylococcus aureus and 35 strains from freshly slaughtered birds, isolated at five commercial slaughterhouses processing chickens or turkeys. Of 112 biochemical and physiological tests used, 74 gave results which differed among the strains. Cluster analysis revealed several distinct groupings which were influenced by strain type, processing plant and bird origin; these included a single group at the 72% level of similarity containing most of the 'endemic' strains.

Predicting microbial growth: the consequences of quantity of data.

Having developed a mathematical model of the growth responses in a laboratory medium of salmonellae (mixed inoculum of Salmonella thompson, S stanley and S. infantis) as affected by pH level, NaCl concentration and storage temperature, the consequences of systematic removal of data has been examined. Three-dimensional plots of fitted response surfaces for the whole data set and the data reduced by three strategies highlighted differences between models and illustrated the consequences of using insufficient data.

Predicting microbial growth: growth responses of salmonellae in a laboratory medium as affected by pH, sodium chloride and storage temperature.

The growth responses of salmonellae (mixed inoculum of Salmonella thompson, S. stanley and S. infantis) as affected by NaCl concentration, pH level and storage temperature were studied in laboratory medium.

The effect of sodium chloride and temperature on the rate and extent of growth of Clostridium botulinum type A in pasteurized pork slurry.

A selective medium was used to enumerate Clostridium botulinum growing in the presence of natural spoilage organisms in a model cured pork slurry. The growth responses of a mixed spore inoculum of six strains of Cl. botulinum type A were studied at 15 degrees, 20 degrees and 27 degrees C with 1.