Nitrocefin is a chromogenic cephalosporin substrate routinely used to detect the presence of beta-lactamase enzymes produced by various microbes. Intact beta-lactam antibiotics act as an analog to penicillin-binding proteins (PBPs) involved in peptidoglycan synthesis. Beta-lactamases hydrolyze the amide bond between the carbonyl carbon and the nitrogen in the beta-lactam ring of susceptible beta-lactams and members of beta-lactam subclasses (including certain cephalosporins). After hydrolysis of the amide bond, the antibiotic lacks the ability to mimic bacterial PBPs and is rendered useless. Visual detection of this process is essentially impossible with most cephalosporins because the shift of ultraviolet absorption from the intact versus hydrolyzed product occurs outside of the visible spectrum. Hydrolysis of nitrocefin, however, produces a shift of ultraviolet absorption inside the visible light spectrum from intact (yellow) nitrocefin (~380 nm) to degraded (red) nitrocefin (~500 nm) allowing visual detection of beta-lactamase activity on a macroscopic level.