TABLE 2.

Statistical analysis of differences in intracellular growth rates in primary human macrophages between categories of MAC strains by the t test

Characteristica	Mean k (SD)b for:		P
	Positive strainsc	Negative strainsd
Clinical relevance	0.3124 (0.1152)	0.1514 (0.1345)	0.0109
mig type A	0.2960 (0.1116)	0.1357 (0.1431)	0.0114
IS1245	0.2788 (0.1219)	0.1414 (0.1519)	0.0378
M. avium species	0.2567 (0.1414)	0.1629 (0.1503)	0.1827
pLR7	0.2748 (0.1492)	0.2069 (0.1486)	0.3881

^aClinical relevance, causing clinical infection. mig type A, RFLP type A in a Southern blot using a mig open reading frame-specific DNA probe. IS1245, presence of copies of this insertion element in the bacterial genome. M. avium species, reactivity with the species-specific rRNA probe. pLR7, reactivity with a DNA probe specific for the origin of replication of the mycobacterial plasmid. 

^bIntracellular growth rates (k) were determined from the slopes between the means for day 0 and day 5. Means and standard deviations from four replicate experiments are given. 

^cStrains positive for the given characteristic. 

^dStrains negative for the given characteristic.