Table 2. Competitive Indices of mixed infections using the WT, ΔSTM1485 and the pQE601485 complemented strains.

	Strain-1	Strain-2	Competitive index of strain 2 with respect to strain 1
			Spleen	Liver	MLN¶
1	WT#	WT§	1.121 ± 0.12	0.975 ± 0.17	1.124 ± 0.09
2	WT#	ΔSTM1485	0.413 ± 0.05**	0.341 ± 0.07**	0.206 ± 0.13**
3	WT#	pQE601485	1.035 ± 0.14	1.367 ± 0.09	1.107 ± 0.12

^# Resistant to nalidixic acid and the parent strain for knock out.

^§ Resistant to Carbencillin. Both WT strains were isogenic.

^¶ Mesentric lymph nodes.

^**p < 0.005 (Student's t-test); statistical difference between 1 and 2.