Studies on the topical treatment of experimental cutaneous leishmaniasis: the therapeutic effect of methyl benzethonium chloride and the aminoglycosides, gentamicin and paromomycin.

BALB/c mice infected with either Leishmania major or Leishmania mexicana were treated twice a day for 10 days with an ointment containing 15% gentamicin or paromomycin, with or without 12% methylbenzethonium chloride (MBCl). It was found that topical application of either paromomycin or MBCl cured the parasite lesion, and that combined treatment with the two compounds had an additive effect. However, after four days' therapy there was a severe inflammatory response at the treatment site, and in most experiments mice relapsed and renewed lesion growth was observed. It is suggested that a non-specific inflammatory reaction may be an important component of the therapeutic response. In further experiments, L. major infected mice treated with paromomycin and MBCl which had cured but not relapsed 58 days after treatment were challenged with a similar dose of the homologous parasite. Lesions developed 16 days post-infection, and the number of parasites recovered from these lesions was similar to that recovered from lesions in control mice. Therefore no protective immunity had been induced by chemotherapy.