Confers high levels of resistance to amoxicillin, benzylpenicillin, piperacillin, ticarcillin and cephalothin. Also hydrolyzes aztreonam at a low level. Not active against ceftazidime, cefotaxime and imipenem. a beta-lactam + H2O = a substituted beta-amino acid Inhibited by clavulanic acid, and at a low level by tazobactam and sulbactam. Belongs to the class-A beta-lactamase family.