In vitro comparison of gentamicin and netilmicin including a regression line for netilmicin.

The results of two different in vitro investigations are presented: a comparison between gentamicin and netilmicin and a presentation of a regression line for netilmicin. The first investigation comprises 335 bacterial strains. The method used is a plate dilution technique and the susceptibility of the strains is given as IC50 values, i.e. 50% inhibiting concentrations. The conclusion of the study is that netilmicin offers no advantage over gentamicin. In the second investigation a regression line is presented giving the relation between IC50 values for netilmicin and the size of the inhibition zone, based upon 109 bacterial strains. For the disc diffusion method a 20-hour prediffusion technique is used. The disc content is 15 micrograms netilmicin base. The results are discussed and a grouping as to susceptibility is proposed based on the IC50 values found and the blood level obtained after scheduled dose of netilmicin.