Regression line analysis for five antibiotics with strains of Clostridium species

The susceptibility of 90 strains of clostridia to 5 antibacterials was determined by the agar plate dilution method and the disc diffusion test. The correlations between minimum inhibitory concentration and inhibition zone were quite acceptable for lincomycin, clindamycin, tetracycline and doxycycline to calculate regression lines by the least square method. The strains showed comparatively wide ranges of susceptibility. For erythromycin, no regression line could be calculated, since all the strains tested were susceptible over a narrow range of concentrations.