Fig. 4.

The circular three-dimensional inoculation (indicated by the arrow) intersected the inhibition zone margins to produce major distortions (i.e., positive three-dimensional test results) that indicated enzymatic inactivation of piperacillin (A), cefamandole (D), cefoperazone (E), CTX (F), and ceftriaxone (G). Distortions did not occur (i.e., negative three-dimensional test results) in tests with aztreonam (B), imipenem (C), CAZ (H), or cefoxitin (I). The outer circle is the plastic rim on the bottom of the petri dish.