A modified rack for the LKB sample processor.

dard disc procedure; (c) the strong synergistic effects inside the zone where the two antibiotics are simultaneously present. Results are easy to read, as are those obtained with penicillin G or other aminoglycosides (amikacin, gentamicin, streptomycin). Although less easy to read, similar results have been obtained by using the Kirby Bauer disc diffusion method (instead of the triple layer technique), penase solution being then directly set on the ampicillin disc after 5 h incubation. A technique based on this principle has been recently published by Lee and Komarmy (1975). It is highly probable that microorganisms situated inside the zone of synergism are killed; definite confirmation of this, however, would be brought about only by simultaneous inactivation of the two