TABLE 1.

Induction of resistance to tachyplesin I^a

Organism	Treatment group	No. of transfer generations	MIC range of tachyplesin I (μg/ml)	Tachyplesin I concn during induction (μg/ml)
E. coli ATCC 25922	Original strain	0	5	0
	Treatment group	80	20–40	5–10
	Treatment group	85	160	5–10
	Treatment group	96	>160	10
	Control group	96	10–20	0
E. coli F41	Original strain	0	5–10	0
	Treatment group	72	20–40	5–10
	Treatment group	78	40–80	5–10
	Treatment group	80	>160	5–10
	Control group	80	10–20	0
P. aeruginosa CGMCC1.2620	Original strain	0	10	0
	Treatment group	60	40–80	5–20
	Treatment group	66	40	5–20
	Treatment group	80	>160	5–20
	Control group	80	10–30	0
A. hydrophila XS91-4-1	Original strain	0	10–20	0
	Treatment group	42	20	5–20
	Treatment group	48	40–80	5–20
	Treatment group	69	>160	5–20
	Control group	42–69	20–40	0

^aInduction strains were successively cultured in MHB supplemented with tachyplesin I (5 to 20 μg/ml), whereas control strains were successively cultured in unsupplemented medium under the same conditions. The MIC was measured using the serial broth microdilution method. The MIC was considered the lowest drug concentration for which no visible growth was observed. Each determination was made using three independent replicates for each line. The strains with the most resistance were used as the evolved resistant strains in the following experiments.