Synergy of fosmidomycin (FR-31564) and other antimicrobial agents.

Fosmidomycin (FR-31564), a phosphonic acid derivative, was combined with cefazolin, cephalexin, ampicillin, carbenicillin, ticarcillin, gentamicin, and trimethoprim. Synergy between fosmidomycin and penicillins or cephalosporins was found for 37 to 52% of the Enterobacteriaceae tested. Synergy with trimethoprim was found against 55% of bacteria isolated, but only 17% of the strains showed synergy between formidomycin and gentamicin. Synergy between fosmidomycin and ticarcillin was shown for 35% of the Pseudomonas isolates. Cefazolin-, ampicillin-, and gentamicin-resistant isolates of various species were synergistically inhibited by fosmidomycin, as were ticarcillin- and gentamicin-resistant isolates. Antagonism was not encountered. This study illustrates another example of synergistic activity of compounds which attack different mechanisms in bacterial cells.