[Lytic action of cefminox against slowly growing bacteria]

Lytic action of cefminox (CMNX) against slowly growing Escherichia coli (E. coli) K-12 JE1011 was compared with that of the related cephamycin cefmetazole (CMZ) or ampicillin (ABPC). The growth rate in doubling time was 30 min. at 37 degrees C. Minimal concentrations of CMNX, CMZ and ABPC showing clear lysis were 0.39, 3.13 and 12.5 micrograms/ml, respectively, under these conditions. When E. coli was cultured at 12 degrees C, the doubling time was 720 and 816 min. which were 24 and 27.2 fold as slow as those at 37 degrees C, respectively. In 12 degrees C culture, the minimal concentrations showing clear lysis were 0.78 (2 fold at 37 degrees C), 25 (8 fold) and 100 micrograms/ml and higher (8 fold or more) with CMNX, CMZ and ABPC, respectively. Therefore, it appeared that the lytic activity of CMNX was not significantly affected by bacterial growth rate and was demonstrated effectively against slowly growing bacteria at a low concentration. We determined release activity of cell wall peptidoglycan fragments by 5 beta-lactam antibiotics in addition to the above-mentioned 3 antibiotics. The results showed that the release activity was not proportional to the MIC and that of CMNX was the strongest among those antibiotics. The rapid and strong bactericidal action of CMNX against bacteria at the early stationary phase was suggested to result from the characteristic lytic action against slowly growing bacteria.