Selective isolation of leptospiras from contaminated material by incorporation of neomycin to culture media.

Incorporation of neomycin to the culture medium was found to be effective in inhibiting Escherichia coli contaminants without interfering with the growth of serotype L. autumnalis. The growth of 12 other Leptospira serotypes was unaffected by the addition of 300 mug of neomycin per ml to Ellinghausen medium or 5 mug/ml to Fletcher medium. Neomycin-containing medium was found to be of value in the isolation of leptospiras from cultures of blood from infected laboratory animals. A higher percentage of isolates was obtained in swine kidneys from an abattoir in medium containing neomycin than resulted from the same medium without antibiotic or with 5-fluorouracil. Contaminated leptospiral cultures growing in media with 5-fluorouracil were purified by subculturing into neomycin-containing media.