In vitro activity of trimethoprim against Borrelia burgdorferi.

A new culture medium has been developed to evaluate the activity of trimethoprim and sulfamethoxazole against Borrelia burgdorferi in vitro. In this specially modified Barbour-Stoenner-Kelly medium, in which antagonizing substances were reduced to a minimum, trimethoprim was more active against Borrelia burgdorferi than against a sensitive strain of Escherichia coli, but sulfamethoxazole was not active against Borrelia burgdorferi.