Oxolinic acid--trimethoprim combination: effects on DNA synthesis and on viability of Escherichia coli.

The synergistic bactericidal effect of the oxolinic acid-trimethoprim combination has been confirmed on an exponentially growing strain of Escherichia coli, and is paralleled by a synergistic inhibition of 14C-uracil incorporation into the bacterial DNA. These data provide experimental support for the postulate that the synergistic effect of quinolone-trimethoprim combinations, observed both in vitro and in vivo, is due to a complementary blockade of bacterial DNA synthesis.