Background: Extended-spectrum beta-lactamases (ESBLs), which allow bacteria to become resistant to commonly used antibiotics against common pathogens such as Klebsiella pneumoniae, are a significant public health concern as their presence severely limits treatment options. Discovery and development of new drug entities are critical to effectively combat infections with these increasingly common antibiotic-resistant variants. Objective: Computational approaches can accelerate and reduce the cost of the discovery phase by screening for inhibitors of “druggable” pathogen enzyme targets in silico. In this study, protein structures of the ESBL enzymes SHV-1 and CTX-M-15 were used as targets in molecular docking experiments to identify potential inhibitors for K. pneumoniae. Methodology: 5000 compounds from the Enamine Real HTS compound database were screened in silico for binding to SHV-1 and CTX-M-15. Twenty-six (26) compounds that were identified to have more favorable interactions compared to Avibactam, a known inhibitor of the target proteins, were tested for cytotoxic activities in vivo using Resazurin Microtiter Assay (REMA) against a K. pneumoniae clinical isolate containing both SHV-1 and CTX-M-15 resistance genes. Results and Conclusion Despite favorable binding energies in in silico screening, most of the compounds exhibited negligible inhibition on the growth of the K. pneumoniae clinical isolate in in vitro assays. This may be attributed to the fact that a phenotypic whole-cell assay, instead of an enzyme-targeted assay, was used for validation. Cell permeability requires a different set of molecular parameters which were not part of the study. Doxorubicin exhibited the highest in vitro bactericidal activity against this strain, which agrees with its known activity against many other bacterial pathogens and may be a promising compound for further lead optimization.
Drug Resistance, Microbial