In vitro evaluation of combined usage of fosfomycin and 5-fluorouracil for selective isolation of Leptospira species.

The combined usage of fosfomycin (FOM) and 5-fluorouracil (5-FU) as selective agents for the isolation of leptospires from contaminated materials was investigated. Additive or synergistic antibacterial activity was apparent with the combination compared with each agent used separately. Of 54 bacterial strains tested, 52 were inhibited, while all 5 Leptospira strains tested were unaffected by the combined addition of FOM (400 micrograms/ml) and 5-FU (100 micrograms/ml) to Korthof medium. Furthermore, this combination successfully supported the selective growth of Leptospira interrogans serovar copenhageni in experimentally contaminated specimens. This FOM-5-FU combination is surmised to be useful for the selective isolation of leptospires from contaminated clinical, pathological, or environmental materials.