The susceptibility of a strain of Leptospira interrogans serogroup icterohaemorrhagiae to amoxycillin, erythromycin, lincomycin, tetracycline, oxytetracycline and minocycline.

The failure of prophylactic penicillin to prevent a laboratory acquired case of Icterohaemorrhagiae leptospirosis prompted determination of the MIC and MBC of amoxycillin, erythromycin, lincomycin, tetracycline, oxytetracycline and minocycline for the infecting strain. Amoxycillin followed by erythromycin were the most effective, with MBCs of 0.5 mg/l after 7 days exposure and 0.1 mg/l after 21 days exposure respectively. Leptospires grew in the presence of high concentrations of tetracycline hydrochloride and oxytetracycline after prolonged incubation. This effect was less pronounced with minocycline, with MIC's of 0.025, 0.05 and 0.1 mg/l after 7, 14 and 21 days exposure respectively. The MIC of lincomycin was 0.25 mg/l at each time interval. These results support the high dose, long duration antibiotic regimens recommended in the literature.