- Adam B Shapiro: Entasis Therapeutics, Waltham, Massachusetts, USA adam.shapiro@entasistx.com. ORCID
Sulbactam is one of four β-lactamase inhibitors in current clinical use to counteract drug resistance caused by degradation of β-lactam antibiotics by these bacterial enzymes. As a β-lactam itself, Sulbactam is susceptible to degradation by β-lactamases. I investigated the Michaelis-Menten kinetics of Sulbactam hydrolysis by 14 β-lactamases, representing clinically widespread groups within all four Ambler classes, i.e., CTX-M-15, KPC-2, SHV-5, and TEM-1 for class A; IMP-1, NDM-1, and VIM-1 for class B; ADC-7, AmpC, and P99 for class C; and OXA-10, OXA-23, OXA-24, and OXA-48 for class D. All of the β-lactamases were able to hydrolyze Sulbactam, although they varied widely in their kinetic constants for the reaction, even within each class. I also investigated the inactivation kinetics of the inhibition of these enzymes by Sulbactam. The class A β-lactamases varied widely in their susceptibility to inhibition, the class C and D enzymes were very weakly inhibited, and the class B enzymes were essentially or completely unaffected. In addition, we measured the Sulbactam turnover number, the Sulbactam/enzyme molar ratio required for complete inhibition of each enzyme. Class C enzymes had the lowest turnover numbers, class A enzymes varied widely, and class D enzymes had very high turnover numbers. These results are valuable for understanding which β-lactamases ought to be well inhibited by Sulbactam. Moreover, since Sulbactam has intrinsic antibacterial activity against species pathogens, these results contribute to understanding β-lactamase-mediated Sulbactam resistance in , especially due to the action of the widespread class D enzymes.