Classification of beta-lactamase-producing bacteria

The resistance of bacteria to beta-lactam antibiotics, penicillins or cephalosporins, is usually associated with the production of beta-lactamase enzymes which are capable of inactivating these compounds. A number of recent surveys have reported a significant increase in the frequency of isolation of beta-lactamase-producing strains of bacteria from infections in general practice in the United Kingdom. A wide variety of bacterial beta-lactamases with different properties have been described and it is now recognised that most bacteria produce a chromosomally-mediated beta-lactamase which is characteristic of each species. In addition, Gram-negative bacteria may acquire beta-lactamases which are mediated by plasmids which are readily transferable by cell to cell contact. Schemes for the classification of bacterial beta-lactamases are outlined.