TABLE 1.

Cross-resistance of bloodstream and procyclic forms of T. brucei brucei strain 427 to megazol and other trypanocides^a

Drug	IC50 (μM)
	Procyclic forms		Bloodstream forms
	Wild type	Resistant (factor of resistance)	Wild type	Resistant (factor of resistance)
Megazol	0.28 ± 0.01	29.24 ± 3.18 (104)*	0.15 ± 0.02	3.20 ± 0.48 (21)*
Nifurtimox	4.89 ± 0.12	37.12 ± 3.84 (7.6)*	5.58 ± 0.86	34.41 ± 4.91 (6.2)*
Benznidazole	2.89 ± 0.20	12.87 ± 1.29 (4.5)**	15.26 ± 3.85	77.36 ± 4.92 (5.2)*
Suramin	15.59 ± 2.61	66.06 ± 4.15 (4.2)**	0.13 ± 0.01	0.32 ± 0.21 (2.5)***
Berenil	10.99 ± 1.50	41.14 ± 1.31 (3.7)*	0.99 ± 0.12	5.18 ± 1.14 (5.2)*
Pentamidine	2.14 ± 0.03	5.06 ± 0.23 (2.4) (NS)	0.04 ± 0.07	0.15 ± 0.01 (3.8)*
Melarsen oxide	0.02 ± 0.00	0.07 ± 0.08 (3.5)*	0.01 ± 0.00	0.05 ± 0.01 (5.0)*
Melarsoprol	2.38 ± 0.08	2.60 ± 0.02 (1.1) (NS)	0.13 ± 0.01	0.30 ± 0.01 (2.3)***
Cymelarsan	0.06 ± 0.00	0.13 ± 0.00 (2.2)***	0.02 ± 0.02	0.07 ± 0.03 (3.5)***
Ethidium bromide	12.15 ± 1.52	16.89 ± 1.73 (1.4) (NS)	2.07 ± 0.68	4.29 ± 0.71 (2.1) (NS)
Isometamidium	9.80 ± 0.79	11.44 ± 0.79 (1.2) (NS)	3.35 ± 0.56	4.33 ± 0.67 (1.3) (NS)
Brilliant green	0.016 ± 0.00	0.053 ± 00 (3.3)	0.003 ± 00	0.003 ± 0.000 (1.0)

^aSensitivities of wild-type and selected megazol-resistant lines to a number of drugs were determined. The factors of resistance indicated in parentheses were calculated as ratios of IC₅₀s for resistant parasites to those for wild-type parasites. Values that were significantly different from that for the control, by Student's t test, are designated by an asterisk(s) (*, P < 0.001; **, P < 0.01; ***, P < 0.05; NS, not significant at P = 0.05). Values are means ± standard deviations (n = 3 independent experiments).