Involvement of thiol metabolism in resistance to glucantime in Leishmania tropica.

Clinical resistance to pentavalent antimonials, in the form of pentostam (sodium stibogluconate) or glucantime (N-methylglucamine antimoniate), has long been recognized as a problem in Leishmaniasis. However, the mechanisms of resistance are unclear. We selected in vitro a Leishmania tropica line resistant to 1.2 mg/mL of Sb(V) of glucantime (GLU-R10). The cell line has a stable phenotype for at least 6 months and a resistance index of 1400-fold. The resistant line has no cross-resistance to pentostam or to SbCl3 and SbCl5. The resistance to glucantime was reverted by buthionine sulfoximine (BSO) and chlorambucil (CLB); however, thiol analyses by HPLC of wild-type and GLU-R10 cell lines, in the presence or absence of the drug, showed no differences between these two cell lines. The resistant line had a DNA amplification shown as a circular extrachromosomal element (G-circle) of approximately 22 kb. However, the specific probes for gamma-glutamyl cysteine synthetase, ornithine decarboxylase and trypanothione reductase did not recognize the G-circle amplified in the GLU-R10. The G-circle did not arise from the H region and was not related with P-glycoprotein Pgp-MDR- or Pgp-MRP-like genes. Northern blot analysis of the G-circle showed that a single transcript of approximately 6 kb was overexpressed in the resistant line. Molecular characterization of the G-circle would lead to the determination of the gene(s) involved in resistance to glucantime in Leishmania.

Efficacy of a short course (10 days) of high-dose meglumine antimonate with or without interferon-gamma in treating cutaneous leishmaniasis in Guatemala.

Sixty-six Guatemalan men with parasitologically confirmed cutaneous leishmaniasis, due most commonly to Leishmania braziliensis, were randomly assigned to receive one of three treatment regimens: meglumine antimonate (meglumine) for 20 days; meglumine for 10 days; and meglumine for 10 days plus alternate-day injections of interferon-gamma. In each group, meglumine was given intravenously as 20 mg of antimony/(kg of body weight.d). All treatment regimens were associated with similar response rates: the lesions of 19 (90%) of 21 patients who received meglumine for 20 days, 18 (90%) of 20 patients who received meglumine for 10 days, and all 22 patients who received meglumine plus interferon-gamma were completely reepithelialized by 13 weeks. In addition, for patients receiving all treatment regimens, test-of-cure cultures for Leishmania were negative and reactivation of lesions did not occur during 12 months of follow-up. The high efficacy of our 10-day course of meglumine indicates that the currently recommended duration of 20 days may be unnecessary for infections caused by L. braziliensis and suggests that a 10-day course of high-dose antimony should be tested as therapy for cutaneous leishmaniasis in other geographic areas.

Placebo-controlled clinical trial of sodium stibogluconate (Pentostam) versus ketoconazole for treating cutaneous leishmaniasis in Guatemala.

To determine the relative efficacy and toxicity of stibogluconate and ketoconazole for the treatment of cutaneous leishmaniasis, a comparative trial was conducted in which 120 Guatemalan men with parasitologically proven cutaneous leishmaniasis were randomly divided into three treatment groups: sodium stibogluconate (20 mg of antimony per kilogram per day intravenously for 20 days), ketoconazole (600 mg per day orally for 28 days), and placebo. Treatment outcome was influenced by species. Among patients infected with Leishmania braziliensis, 24 (96%) of 25 in the stibogluconate group but only 7 (30%) of 23 in the ketoconazole group responded. Among Leishmania mexicana-infected patients, only 4 (57%) of 7 in the stibogluconate group but 8 (89%) of 9 in the ketoconazole group responded. These differences emphasize the importance of speciation in the treatment of leishmaniasis.

Cutaneous leishmaniasis in Guatemala: comparison of diagnostic methods.

A comparison was made of methods used to diagnose suspected cutaneous leishmaniasis in Guatemala. The most sensitive method was a combination of thin smears made from superficial scrapings of the ulcers and inoculation of culture medium with either aspirates or scrapings. The diagnosis was confirmed in 252 (70%) of 362 patients. Ability to cultivate Leishmania was correlated with the concentration of amastigotes seen on thin smears. Leishmania were cultured in 42 (27%) of 153 patients with no amastigotes found in 400 oil-immersion fields and in 174 (83%) of 209 patients with at least 1 amastigote. No difference in diagnostic outcome was found when we compared smears or cultures taken from the center or the border of the ulcer or from an incision made tangential from the ulcer. We found no difference when we compared smears obtained with scalpels, capillary tubes, or dental broaches. The use of scrub brushes soaked in iodine neither decreased the rate of culturing parasites nor decreased contamination rates.

Placebo-controlled clinical trial of meglumine antimonate (glucantime) vs. localized controlled heat in the treatment of cutaneous leishmaniasis in Guatemala.

Sixty-six Guatemalans with parasitologically proven cutaneous leishmaniasis were randomly and equally divided into 3 treatment groups: those receiving meglumine antimonate (Glucantime), 850 mg antimony/day im for 15 days; those receiving localized controlled heat from a radio-frequency generator, 50 degrees C for 30 sec, 3 treatments at 7 day intervals; and those receiving treatment with a placebo. Of 53 isolates identified, 40 were Leishmania braziliensis braziliensis and 13 were L. mexicana mexicana. Thirteen weeks after beginning treatment, the number of patients from each group with completely healed and parasitologically negative lesions were as follows: meglumine antimonate, 16 (73%); localized heat, 16 (73%); and placebo, 6 (27%). The cure rate for those with infections due to L. b. braziliensis in each group was as follows: meglumine antimonate, 11 out of 14 (79%); controlled heat, 9 out of 14 (64%); and placebo, 0 out of 11.

Cutaneous leishmaniasis in Guatemala: isoenzyme characterization of isolates from humans.

Leishmania organisms cultivated from cutaneous lesions of humans in Guatemala were characterized by cellulose acetate electrophoresis. Six isolates had electrophoretic enzyme patterns identical to World Health Organization reference strains of Leishmania braziliensis braziliensis, and 5 had patterns identical to reference strains of Leishmania mexicana mexicana.