Detection of beta lactamase producing bacteria by Cefinase: comparison with three other methods

Nine hundred and sixty-seven strains of gram positive and gram negative bacteria were tested for the production of beta lactamase by Cefinase and the results were compared with acidometric microtiter, disc diffusion and antibiotic dilution procedures. A total of 420 strains of bacteria had a minimal inhibitory concentration (MIC) of more than 2.0 micrograms/ml for penicillins. They consisted of 23 strains of Neisseria gonorrhoeae, 36 of Haemophilus influenzae, 188 of Staphylococcus aureus and 173 strains of S. epidermidis. All the penicillin resistant strains gave positive results for beta-lactamase with Cefinase and acidometric method within 60 min. All the 547 strains of penicillin sensitive bacteria (MIC less than or equal to 2.0 micrograms/ml) were negative for beta-lactamase production by both methods.