Effect of glucantime on field and patient isolates of New World Leishmania: use of growth parameters of promastigotes to assess antimony susceptibility.

The effect of pentavalent meglumine antimoniate (glucantime) on the growth kinetics of promastigotes of 13 South American Leishmania strains isolated from patients, sylvatic reservoirs, and vectors was studied. Four of five L. (Viannia) braziliensis human isolates were obtained from drug-responsive patients and one was isolated from an unresponsive mucocutaneous-type infection. Studies involved the cell yield at the late log phase, the growth rate, and the growth-curve patterns of promastigotes in vitro. Restriction-fragment-length polymorphism, pulsed-field gel electrophoresis, and hybridization with the gene coding for a P-glycoprotein from L. (V.) guyanensis were used in an attempt to correlate the resistance phenotype with gene amplification. Consistent differences observed in both cell yield and growth rate among the isolates in the presence of glucantime indicated these parameters to be good criteria for the estimation of susceptibility to glucantime. Drug susceptibility varied widely between strains, indicating a great genetic heterogeneity of the isolates. Five L. (V.) braziliensis strains and three L. (V.) guyanensis strains were shown to be susceptible to glucantime. Five isolates were resistant, four of which were obtained from sylvatic vectors and one, from a patient with an unresponsive mucocutaneous infection. Molecular analyses of total DNA indicated the presence of a pgpA-related gene in all strains tested. No amplified sequence could be detected, suggesting that pgpA amplification is not involved in glucantime resistance in these wild Leishmania strains.