Abstract

The use of liquid media to detect the production of beta-lactamase by beta-lactamase producing organisms has been compared with the conventional method of inoculation on to agar media. Pharyngeal cultures were obtained from 162 children treated with penicillin for acute tonsillitis. beta-lactamase producing organisms were detected within 72 h in 80 (49%) of the specimens inoculated on to agar media, while beta-lactamase production was found in 76 (47%) of the specimens after their incubation in liquid media for 24 h. Twenty one of the cultures were positive only after anaerobic incubation while in liquid media while nine were positive only after aerobic incubation. Incubation in liquid media enabled detection of beta-lactamase activity in 53 of the 76 (70%) specimens within 12 h.