A twofold serial dilution is performed in 1.0 ml amounts fro…

A twofold serial dilution is performed in 1.0 ml amounts from a MH broth containing ampicillin.  Tubes 1 through 11 are incubated overnight at 35 degrees C.  Tubes 6 through 11 show visible turbidity while tubes 1 through 5 show no signs of growth.  Tubes 1 through 5 are plated on blood agar and incubated overnight.  Plates 1 through 4 show no growth, while several colonies are observed on plate 5.  The MIC would be determined from which tube?