Table 1: Detection of GBS following 9-hour incubation in the presence of erythromycin and dilutions of clindamycin. Isolate A (noninducible resistance to clindamycin) compared with isolate B (inducible resistance capable). ++++ OD > 3.0. +++ OD 2.0–2.9. ++ OD 1.0–1.9. + OD 0.1–0.9. − OD 0–0.099.

107 bacteria/mL106 bacteria/mL105 bacteria/mL104 bacteria/mL
Isolate AIsolate BIsolate AIsolate BIsolate AIsolate BIsolate AIsolate B

Clindamycin 0 μg/mL
Erythromycin 1.0 μg/mL
+++++++++++++++++++++++++++++++

Clindamycin 0.5 μg/mL
Erythromycin 1.0 μg/mL
++++++++

Clindamycin 0.05 μg/mL
Erythromycin 1.0 μg/mL
+++++++++

Clindamycin 0.005 μg/mL
Erythromycin 1.0 μg/mL
+++++++++