Abstract
With Ericsson's disc diffusion method 40% of methicillin-resistant strains of Staphylococcus aureus, according to the definition of Parker and Jevons, were reported as sensitive. At 30°C incubation no such “falsely sensitive” strains occurred.
The heterogeneity of methicillin-resistance seemed to be fairly constant. After cloning on methicillin plates the strains acquired a higher resistance. Usually they segregated back rapidly, but some strains remained unchanged for several generations before they slowly segregated.