[In vitro sensitivity of Plasmodium falciparum to mefloquine, quinine, amodiaquine, chloroquine, pyronaridine and sulfadoxine/pyrimethamine in south Yunnan]

Abstract

The sensitivity of P. falciparum to mefloquine, quinine, amodiaquine, chloroquine, pyronaridine, and sulfadoxine/pyrimethamine (MEF, QNN, AMO, CHL, PYR, S/P) was tested using in vitro microtest in south Yunnan Province in 1992. The ID50 were 46, 480, 52, 150, 15 and 2 x 10(4)/25 x 10(2) nmol/L, respectively; ID95 were 160, 1,536, 292, 680, 60 and 24 x 10(5)/3 x 10(5) nmol/L, respectively. All the isolates (30) were sensitive to MEF and QNN; 100% (30/30) and 96.7% (29/30) isolates were found to be resistant to AMO and CHL, the cross-resistance rate was 100% to the two drugs. One of 5 isolates exhibited resistance to PYR. The results suggest that the P. falciparum was susceptible to MEF and QNN, but was resistant to AMO, CHL and S/P. CHL-resistant P. falciparum showed a marked cross-resistance to AMO, but not to MEF, QNN, and S/P; AMO-resistant P. falciparum exhibited cross-resistance to CHL, but not to MEF, QNN, and S/P.