TABLE 1.

Analysis of the combined effect of gentamicin and gallium in inhibition of growth of F. tularensis in different experimental models

Experimental model	% inhibition with gentamicin and galliuma		No. of experiments	Combined effect of gentamicin and gallium (P value)c
	Predictedb	Observed
CDM	66 ± 7	88 ± 9	4	Synergistic (<0.01)
BMDM, 6 h	29 ± 19	53 ± 6	3	Synergistic (<0.05)
BMDM, 17 h	87 ± 5	98 ± 4	3	Synergistic (<0.05)
Livers of mice	99.7 ± 0	99.6 ± 1	2	Additive (>0.05)

^aValues are means ± standard deviations for observations derived from two to four separate experiments.

^bIf two drugs work independently, the combined percent inhibition, Y_ab,P, can be predicted using the complete additivity of the probability theory, i.e., Y_ab,P = Y_a + Y_b − Y_aY_b, where Y_a is the observed percent inhibition of drug A and Y_b is the observed percentage inhibition of drug B. This formula was used to calculate the predicted combined percent inhibition by gentamicin and gallium.

^cSynergistic indicates that in each separate experiment, the observed values were significantly different from the predicted value according to the one-sample t test. Additive indicates that in each separate experiment, the observed values were not significantly different from the predicted value according to the one-sample t test.