Understanding the molecular interactions of inhibitors against Bla1 beta-lactamase towards unraveling the mechanism of antimicrobial resistance

This study evaluated the inhibitory potential of various beta-lactamase inhibitors such as mechanism-based inhibitors (MBIs), carbapenems, monobactam, and non-beta-lactam inhibitors against Bla1, a class-A beta-lactamase encoded by Bacillus anthracis. The binding potential of different inhibitors was estimated using competitive kinetic assay, isothermal titration calorimetry, and Biolayer interferometry. We observed that tazobactam has better inhibition among other MBIs with a characteristics inhibition dissociation constant of 0.51 ± 0.13 μM. Avibactam was also identified as good inhibitor with an inhibition efficiency of 0.6 ± 0.04 μM. All the MBIs (K_D = 1.90E-04 M, 2.05E-05 M, 3.55E-04 M for clavulanate, sulbactam and tazobactam) showed significantly better binding potential than carbapenems (K_D = 1.02E-03 M, 2.74E-03 M, 1.24E-03 M for ertapenem, imipenem and biapenem respectively). Molecular dynamics simulations were carried out using Bla1-inhibitor complexes to understand the dynamics and stability. The minimum inhibitory concentration (MIC) was carried out by taking various substrates and inhibitors, and later it was followed by cell viability assay. Together, our study helps develop a proper understanding of Bla1 beta-lactamase and its interaction with inhibitory molecules. This study would facilitate comprehending the catalytic divergence of beta-lactamases and the newly emergent resistant strains, focusing on the new generation of therapeutics being less prone to antimicrobial resistance.