Which of the following indicates a positive reaction for the beta-lactamase chromogenic cephalosporin method?

The beta-lactamase chromogenic cephalosporin method is a specific biochemical test used to detect the presence of beta-lactamase enzymes produced by certain bacteria. These enzymes confer resistance to beta-lactam antibiotics, including penicillins and cephalosporins. The method involves the use of chromogenic cephalosporin substrates, which, upon hydrolysis by the beta-lactamase enzyme, lead to a color change in the medium.

A positive reaction, indicated by a color change, occurs when the substrate is cleaved by the beta-lactamase enzyme, resulting in the release of a chromogenic product that alters the color of the medium. This visual cue allows for the easy identification of beta-lactamase-producing organisms in a laboratory setting.

Other potential indicators, such as the production of acid, reduction of nitrates, or decolorization of a starch-iodine mixture, are not relevant to this specific test. Acid production and nitrate reduction pertain to different metabolic pathways and tests, while the starch-iodine test assesses the presence of starch breakdown, unrelated to beta-lactamase activity. Thus, the observation of a color change is the definitive indicator of a positive result