Beta-lactamase alteration of betalactam inhibitory zones

Abstract
A disk approximation test, in which the inhibitory zone of one beta-lactam antibiotic is truncated under influence of another beta-lactam (e.g. cefoxitin), was used as a screen for the presence of inducible betalactamase. By using beta-lactamase extracts and a specific inhibitor, it was shown that chromosomal beta-lactamase can indeed be the sole cause of truncated beta-lactam inhibitory zones.