The limitation of the ABAC system for the automated antibiotic sensitivity test is the fixed number of antibiotics to be assayed. This limit is partially overcome by the up-dating of ABAC disposables necessary both for bacterial infectious pathology (considerably various and dinamic) and bacterial resistance to antibiotics. Accordingly, research is constantly producing new antibiotics particularly in the beta-lactamine and aminoglycoside fields. In these groups new antibiotics must be found to substitute the old ones in the ABAC disposables, in particular in relation to Gram-negative bacteria (urinary or not). The preparation of a rotor for experimental use containing new antibiotics not present on the market is proposed to evaluate their validity through a rapid and standardized method.