In vitro brodimoprim activity on bacterial strains.

The antibacterial activity of brodimoprim (BDP) was compared to that of trimethoprim (TMP) and to 4 other antibiotics (3 beta-lactams and one macrolide). The 237 tested strains were selected predominantly among bacteria isolated from respiratory tract infections: 133 Gram-negative bacilli and 98 Gram-positive cocci. The study included: determination of minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of all antibiotics of the study for all isolates; kinetics of bactericidal activities for selected susceptible strains; correlation between MICs and inhibition zones (standard agar diffusion technique) of BDP (regression line). The results of the study showed: [1] no significant difference between in vitro activities of BDP and TMP against all tested strains; [2] low MICs of both drugs for Haemophilus influenzae, Legionella pneumophila, Staphylococcus aureus (methi-S and methi-R), Streptococcus pneumoniae (peni-S), streptococci and enterococci; [3] kinetics of bactericidal activities indicating 4 log decrease of inoculum size with BDP for Staph. aureus, S. pneumoniae, H. influenzae, within 7 hours; [4] correlation was established between inhibition zones and MICs of BDP, with a coefficient of correlation r = 0.88 for 182 strains. In conclusion, BDP exhibited in vitro antibacterial and bactericidal activities at least equal to that of reference drugs against most respiratory pathogens; BDP was superior to comparators against methi-R staphylococci and enterococci.