Correlation of minimum inhibitory concentration and beta-lactamase activity.

The beta-lactamase activity of 510 recently isolated Enterobacteriaceae was investigated with a quantitative photometric test. Beta-lactamase could be detected in 55 percent of the Enterobacteriaceae. At the same time minimal inhibition concentration (MIC) of beta-lactam antibiotics was determined. There was no correlation between MIC values and lactamase activity. For correct antibacterial therapy the clinician requires information on the lactamase activity of isolated bacteria in addition to the antibiogram. The qualitative test is useful for screening.