Autobac I procedure to assess susceptibility to Cefaclor

Agar dilution and Autobac I tests were performed to compare the susceptibility of 1,000 bacterial isolates to cefaclor and cephalothin. The standard Autobac methodology will correctly predict resistance to cefaclor. The test methodology seems to influence in vitro results, since more strains of gram-negative bacteria were susceptible to cefaclor by the Autobac I method than by the agar dilution test.