Susceptibility towards Ampicillin. Broth cultures from M. bovis BCG(pAS-MDP1) and M. bovis BCG(pMV261) were diluted into Middlebrook 7H9 broth without or with Ampicillin (25 μg ml-1) to give an initial OD (600) nm of 0.02 to 0.04. The growth of the strains was monitored by determination of the ATP content with a luciferase assay during 22 days. The diagram displays the percent growth of the strains in medium with Ampicillin in relation to the growth in medium without Ampicillin. The columns represent the mean of three independent cultures with the standard deviation. The double asterisks indicate values that varied very significantly (P < 0.01) according to the student's t test.