A Note on Penicillinase Production and Penicillin Sensitivity of Staphylococci in the Disc Test

SUMMARY The sensitivities were determined of 306 isolates of Staphylococcus aurcus and of a smaller number of Staph, albus to various penicillin derivatives, as estimated by a conventional disc method, and their production of penicillinase (β‐lactamase). Many strains of Staphylococci which gave restricted but clear zones of inhibition round discs were shown to produce β‐lactamase. It is suggested that all strains of staphylococci showing such restricted inhibition zones round discs of β‐lactamase‐sensitive penicillins should be reported as relatively resistant to these derivatives.