β-Lactams are a large class of antibiotics that includes penicillins, cephalosporins, carbapenems, and monobactams. Resistance against β-lactam antibiotics can result from the production of β-lactamases, which is a common mechanism employed by Gram-negative bacteria. Sulbactam is a penicillanic acid sulfone that acts as an irreversible inhibitor of β-lactamases. It is effective against a wide variety of serine β-lactamases produced by common Gram-negative and Gram-positive aerobes and anaerobes. However, it is not effective against metallo-β-lactamases, cephalosporinases, or oxacillinases.