Enhanced antibacterial effect of erythromycin in the presence of 3,5-dibenzoyl-1,4-dihydropyridines

Fifteen 3,5-dibenzoyl-1,4-dihydropyridines (BzDHP, GB1-GB15) (nifedipine (N P) analogs) were tested on three different E. coli strains. The compounds h ad relatively high MIC values on these strains. In combination with erythro mycin (Er), compounds (G1,3,4,6,7,10,12) reduced MIC values of El: I When t he BzDHPs were tested on E. coli Gy-1/Ap(sen) . Er-res strain isolated from a clinical specimen, the reduction of MIC values were similar to the previ ous strains, but, not identical. In the polyresistant clinically isolated E . coli Gy-2/Ap(res) . Er-res strain, the MIC values of Er were slightly red uced in the presence of GB1-GB7. Compound GB12 was the most effective in en hancing the activity of EI; and was selected for plasmid elimination studie s. However, GB12 itself had no antiplasmid effect and did not alter the pro methazine induced plasmid elimination.