TABLE 2.

MIC₅₀s, MIC₉₀s, and geometric mean MICs of four antibiotics for S. milleri group^ab

Drug and parameter	μg/ml
	S. intermedius	S. constellatus	S. anginosus
Penicillin
MIC50	0.06	0.06	0.06
MIC90	0.06	0.25	0.25
Mean	0.037	0.089	0.049
Ampicillin
MIC50	0.12	0.25	0.12
MIC90	0.25	0.5	0.25
Mean	0.14	0.23	0.078
Ceftriaxone
MIC50	0.06	0.25	0.25
MIC90	0.12	0.5	0.5
Mean	0.079	0.23	0.16
Clindamycin
MIC50	0.03	0.06	0.06
MIC90	0.25	0.25	16
Mean	0.060	0.053	0.21

^aDifferences in MICs of beta-lactam antibiotics for the three species were significant (P < 0.05), but differences in MICs of clindamycin were not (P = 0.09) (Kruskal-Wallis test). 

^bMIC of penicillin for S. constellatus was greater than that for S. intermedius; MIC of ampicillin for S. constellatus was greater than that for S. anginosus; MICs of ceftriaxone for S. constellatus and for S. anginosus were greater than that for S. intermedius; P < 0.05 for all comparisons (Mann-Whitney test).