TABLE 1.

Inhibitory concentrations of lactoferrin and transferrin^a

Microorganism	pH	Lactoferrin (μM)		Transferrin (μM)
		IC90	IC50	IC90	IC50
P. aeruginosa	5.5	0.5	ND	2	ND
	7.4	1	0.5	4	1
	7.4	2*	1*	NS*	NS*
L. lactis	5.5	0.062	ND	NS	NS
	7.4	0.125	ND	NS	NS
	7.4	NS*	NS*	NS*	NS*

^aP. aeruginosa or L. lactis cells were incubated (90 min) with different concentrations (ranging from 0.03 to 25 μM) of lactoferrin or transferrin in 10 mM MES (pH 5.5) or 10 mM Tris-HCl (pH 7.4). Cell viability was calculated with respect to the nontreated cells (control), using a plate count method. ND, not determined; NS, not susceptible at ≥25 μM transferrin. *, values obtained with iron-saturated proteins.