TABLE 3.

Growth and virulence of P. aeruginosa PAO1 and its siderophore production mutants inoculated intranasally into immunosuppressed mice

Strain inoculated	Count of viable bacteriaa detected in:			Lethality in miceb at:
	Lung		Blood (12 hpi)
	1 hpi	12 hpi		12 hpi	24 hpi	48 hpi
PAO1	5.73 ± 0.37	8.01 ± 0.41 (2.28)	>4.21 ± 0.65	3/7	6/7	6/7
PAD02	6.03 ± 0.18	8.24 ± 0.32 (2.22)	>4.66 ± 0.58	3/7	6/7	7/7
PAD06	6.31 ± 0.07	7.61 ± 0.46 (1.30)d	3.11 ± 0.73c	0/7	4/7	5/7
PAD07	6.33 ± 0.10	7.22 ± 0.58c (0.89)d	<2.36 ± 0.39d	0/7	0/7d	7/7

^a Samples were collected from three or five mice a group at 1 and 12 hpi, respectively, and assayed for viable bacteria. Values are mean log₁₀ CFU ± SDs in the lung or in 1 ml of blood. The detection limit of bacteria in the blood was 2.00 to 5.00; the limit values were included for calculation of the mean, if data were below the limit. Values in parentheses represent bacterial growth, expressed as the mean of the increases in the count (each count in the group at 12 hpi minus the mean count at 1 hpi), in log₁₀ CFU. SDs for the mean increases in the counts are theoretically identical to those for mean counts at 12 hpi. 

^bNumber of dead mice/number of mice inoculated for observation of bacterial virulence. 

^c Significantly different (P < 0.05) from value for PAO1-inoculated group as calculated by Student's t test (for means) or Fisher's exact probability test (for frequencies). 

^dSignificantly different (P < 0.01) from value for PAO1-inoculated group as calculated by Student's t test (for means) or Fisher's exact probability test (for frequencies).