These enzymes hydrolyze drugs such as ceftazidime, cefotaxime and aztreonam, but have little effect on the cephamycins - cefoxitin and cefotetan. These enzymes can be blocked by beta-lactamase inhibitors such as clavulanic acid. The prevalence of ESBL-producing bacteria in most hospitals remains unknown in spite of numerous reports of nosocomial outbreaks of infection due to these organisms. Difficulty in the detection of ESBL production using routine antimicrobial susceptibility testing methods has been well documented. Extended spectrum beta lactamase.
Examples are cefotaxime, ceftriaxone, ceftazidime, aztreonam and cefpodoxime.
These enzymes are not active against the cephamycins, and are inhibited by clavulanic acid. Klebsiella pneumoniae and Escherichia coli most frequently are associated with ESBL production. The percentage of isolates expressing this phenotype is very variable although a recent study from the United States reported 83 ESBL-producing isolates from 906 consecutive isolates of Enterobacteriaceae over a 20 week period. The detection methods used for K. pneumoniae and E. coli have not been shown to be valid for other ESBL-producing bacteria. When to test for ESBL production 4.2.1 All clinically significant isolates of E. coli or K. pneumoniae should be tested against beta-lactam drugs.