[Statistical regression analysis for four new cephalosporins (author's transl)]

The MIC (agar dilution method) and the zone diameter (disk diffusion) were determined for two hundred and sixteen of the most frequently bacterial strains found in hospitals in order to establish the regression curves for four new cephalosporins : cefotaxime, cefoperazone, cefotiam, moxalactam. The dta (MIC, zone size) were represented by a series of points (Mi (Xi Yi) in semilogarithmic rectangular co-ordinates expressed as : Xi = log2 MIC + 7 ; Yi = zone diameter. Firstly, we tried to fit a regression polynomial to this series of points progressing from degree 1, simple equation (standard regression line) 2, 3, etc. in order to reduce if need be, the deviation between the model (polynomial) and the empirical data. For these four cephalosporins a regression polynomial was obtained. Secondly, the global series was divided into three series of points Mi corresponding to three ranges of MIC : MIC less than or equal to 4 microgram/ml ; 4 less than or equal to 16 micrograms/ml; MIC greater than or equal to 16 microgram/ml. A regression line was obtained for each series and compared with each other and each one with the global regression line (they do not coincide statistically). Concerning these antibiotics, it is better to use a regression polynomial rather than apply a standard regression line.