[Studies on in vitro antibacterial effects of amoxicillin against Proteus mirabilis IID-994 and Escherichia coli NIHJ JC-2 (author's transl)].

Amoxicillin (AMPC), a synthetic penicillin for oral use, was studied in the aspect of in vitro antibacterial efficiencies brought about by different schedules of AMPC-treatment. Using Proteus mirabilis IID-994 and Escherichia coli NIHJ JC-2 as test strains. The results were obtained as follows. 1. The antibacterial effects of AMPC against P. mirabilis IID-994 and E. coli NIHJ JC-2 were shown to be bactericidal rather than bacteriostatic and the numbers of viable cells were decreased in proportion to the length of exposing time to AMPC. 2. The decrease of viable cells was independent on the drug at which level concentration we tested, namely, it was not much changed by the level of AMPC at least among 1 to 4 times of minimal inhibitory concentration. 3. The length of time retaining growth-inhibitory ability was longer in the case of treating continuously for 4 hours than that of contacting twice for 2 hours at intervals of 6 hours, although the levels of viable cells after 12 hours incubation were almost same in both cases. 4. The level of bactericidal effect and the length of growth-inhibitory time were proportional to the length of exposing time to AMPC.