Beta-lactamases are the most common cause of beta-lactam resistance in Gram-negative bacteria. With third-generation and fourth-generation cephalosporins being introduced into practice, new beta-lactamases have evolved, able to hydrolyze these antibiotics. AmpC-type beta lactamases (cephalosporinases) are serine enzymes with the ability to hydrolyze penicillins, monobactams and cephalosporins of all generations, including cephamycins. Over the last two decades, transferable plasmid-mediated class C beta-lactamases have been reported with increasing frequency. The genes for resistance to other groups of antibiotics are usually carried on the same mobile element as the AmpC genes. A reliable method for AmpC detection in routine diagnosis has not been available yet. The issue of AmpC-type beta lactamases is summarized, including their identification, interpretation of susceptibility test results and recommended treatment of infection caused by AmpC producers.

        Key words: resistence – cephalosporins – beta-lactamases – enterobacteria – AmpC