Which procedure describes how to determine the MBC after a broth dilution assay?

Perform Gram stain on the clear tubes and if no cells are visible under microscopy the lowest concentration without cells on the slide is the MBC.

Store the clear tubes at 4°C for 48 hours and if turbidity does not develop during cold incubation consider that the highest concentration tested is the MBC without subculture steps.

Take aliquots from tubes that showed no visible growth, plate on antibiotic-free agar, incubate, and identify the lowest original antibiotic concentration that produces no growth on the antibiotic-free plates as the MBC.

Measure the optical density of the clear tubes with a spectrophotometer; the lowest concentration with an optical density below 0.05 is the MBC and no plating is required.