Rapid test used to isolate colonies of Neisseria gonorrhoeae , Staphylococcus sp., Haemophilus influenzae and anaerobic bacteria for the production of Β-lactamase: Quarter inch disc impregnated with nitrocefin, a chromogenic cephalosporin When a bacterium produces Β-lactamase in significant quantities, the yellow-colored disc turns red in the area where the isolate is smeared