title: Production and characterization of stable amphotericin-resistant amastigotes and promastigotes of Leishmania mexicana.
abstract: The sensitivities of Leishmania mexicana amastigote and promastigote forms to amphotericin B were investigated in vitro and found to be strongly influenced by the culture media used. When differences in culture media were minimized, there was no significant difference in the 50% inhibitory concentration values between the two life cycle stages. Stable amphotericin B-resistant amastigote and promastigote lines were produced by the application of increasing drug pressure to long-term cultures. Lines capable of growth in concentrations of amphotericin B lethal to normal parasites were produced. Compared to normal parasites, these amphotericin-resistant lines showed marked differences in membrane sterol compositions, with very high levels of 4,14,dimethyl-cholesta-8,24-dienol and other methyl sterols. They also showed a consistent morphological feature, the presence of multilamellar membrane-like material in the flagellar pocket, revealed by transmission electron microscopy. Amphotericin-resistant parasites were capable of infecting BALB/c mice, but the resulting lesion growth was slower than that after infection with normal parasites. However, unlike normal parasites, the amphotericin-resistant parasites were unaffected by experimental chemotherapy with amphotericin B. These results show that amphotericin B resistance could arise as a result of increased clinical use of amphotericin B therapy.
authors.affiliation: Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom.
authors.forename: Hamdan I
authors.initials: HI
authors.lastname: Al-Mohammed
authors.forename: Michael L
authors.initials: ML
authors.lastname: Chance
authors.forename: Paul A
authors.initials: PA
authors.lastname: Bates
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D000981:Antiprotozoal Agents / Q000494:pharmacology* / Q000627:therapeutic use; D003470:Culture Media; D004351:Drug Resistance; D005260:Female; D007894:Leishmania mexicana / Q000187:drug effects* / Q000254:growth & development* / Q000472:pathogenicity; D016773:Leishmaniasis, Cutaneous / Q000188:drug therapy / Q000469:parasitology; D051379:Mice; D008807:Mice, Inbred BALB C; D021261:Parasitic Sensitivity Tests
chemical_list: D000981:Antiprotozoal Agents; D003470:Culture Media; D000666:Amphotericin B