Table 2.

Relationship between DHFR point mutations in Kenyan field isolates of P. falciparum and in vitro chemosensitivity to the antifolates SD and DDS

DHFR phenotypeaIC50(n)b
SDDDS
Group 1
 108(−) 51(−) 59(−)7.42 ± 6.0 (5)1.27 ± 2.1 (5)
 108(+) 51(−) 59(−)37.20 (1)2.98 (1)
 108(+) 51(+) 59(−)18.79 (1)10.16 (1)
 108(+) 51(−) 59(+)10.64 ± 9.6 (7)2.98 ± 3.0 (7)
  Total11.97 ± 10.73 (14)2.98 ± 3.24 (14)
Group 2
 108(+) 51(+) 59(+)29.77 ± 17.3 (18)12.0 ± 8.5 (18)
  • a 108(−), Ser-108 (wild type); 108(+), Asn-108; 51(−), Asn-51 (wild type); 51(+), Ile-51; 59(−), Cys-59 (wild type); 59(+), Arg-59.

  • b IC50s are expressed in micromolar concentrations; values are means ± standard deviations;P < 0.01 for all values.