STATISTICAL APPROACH FOR COMPARISON OF THE GROWTH-RATES OF 5 STRAINS OF STAPHYLOCOCCUS-AUREUS

The interaction of temperature (10, 14, 25, 31, and 37 degrees C), pH (pH 5, 5.6, 6.5, 7.4, and 8), and NaCl (0, 2, 5, 8, and 10%) in a labo ratory medium affects the specific growth rate of Staphylococcus aureu s, From growth curves obtained by the turbidimetric technique, a nonli near model in which the specific growth rate (mu) is fitted directly, without data transformation and with the residual error variations tak en into account, is proposed, This model correctly fits experimental d ata and gives more biological information than the quadratic polynomia l model, Moreover, the comparison of five strains of S. aureus was per formed by a principal-component analysis in which the specific growth rate was the identifying characteristic for S. aureus strains, The res ults obtained from model coefficient comparison among the five strains and from multivariate data analysis allow the same classification of strains to be performed, Two of them have similar behaviors during foo d spoilage, two others could be distinguished by their capacity to gro w at a low temperature,,whereas the last one was markedly different fr om the others.