Medical Definition of beta–lactamase
: any of various bacterial enzymes that inactivate beta-lactam antibiotics (such as penicillin and cephalosporin) by hydrolyzing them When confronted with an antibiotic, a number of disease-causing bacteria will retaliate by making an enzyme called beta-lactamase …—Diana Morgan and Terence Monmaney, Science, July/August 1985 The most common mechanism of resistance to β-lactam antibiotics is the bacterial production of an enzyme called β-lactamase, which breaks one of the antibiotic's chemical bonds, changing its structure and preventing it from inhibiting the enzyme transpeptidase.—K. C. Nicolaou et al., Scientific American, May 2001 ◆Beta-lactamase was originally used only to refer to bacterial enzymes that inactivated penicillin. As additional types of beta-lactam antibiotics were introduced, other bacterial beta-lactamases were identified. —compare penicillinase
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