KPC-2

Klebsiella pneumoniae, a Gram-negative bacterium, poses a significant public health threat due to its resistance to various antibiotics, including β-lactams and carbapenems. This resistance is mainly due to the production of Klebsiella pneumoniae carbapenemases (KPCs). The issue of KPC-2 and its variant, KPC-3, by K. pneumoniae strains, results in resistance to the substrate imipenem and β-lactamase inhibitors. Using Schrodinger software, we performed a high-throughput virtual screening of 374 compounds from the ChemDiv natural compound library in this study, targeting KPC-2 and KPC-3. The top compounds were identified using Extra Precision (XP) mode. Molecular dynamics simulations (MDS) were performed for 500 ns using GROMACS. Among the compounds, N075-0013 and N098-0051 for KPC-2 and N025-0014 and N099-0011 for KPC-3 exhibited binding energies ranging from -5.40 to -7.01 kcal/mol against both KPC-2 and KPC-3. The complexes formed with these compounds remained stable in their dynamic environments, suggesting their potential as effective inhibitors of KPC-2 and KPC-3. These results underscore the potential therapeutic promise of these compounds, justifying further in vitro and in vivo validation for their development as inhibitors of Klebsiella pneumoniae carbapenemases.

E. coli ST8346 is a unique strain associated with the potential carriage of multiple carbapenemases. Three unique E. coli ST8346 isolates were identified, each concurrently harboring multiple carbapenemases, including bla_NDM-5, bla_KPC-2, and/or bla_OXA-181. This study aimed to characterize the genetic and plasmid structures of these isolates to understand their transmission and resistance mechanisms.

Antibiotic resistance profiles, genetic relatedness, and plasmid structures were determined using antibiotic susceptibility testing, multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), S1 nuclease PFGE, and long-read sequencing.

All the strains were carbapenem resistant. PFGE revealed close genetic relationships among the isolates, despite the lack of geographical or epidemiological connections. bla_NDM-5, bla_KPC-2, and bla_OXA-181 were located on separate plasmids. Plasmids harboring bla_NDM-5 showed genetic similarities to bla_NDM-5-bearing IncF plasmids in the United Kingdom. The IncA/C plasmids harboring bla_KPC-2 had identical sequences resembling a plasmid from a K. pneumoniae strain in Taiwan, except for the bla_KPC-2 region, which matched a strain from China, indicating a hybrid plasmid.

This study is the first to identify and characterize the coexistence of bla_NDM-5, bla_KPC-2, and bla_OXA-181 in E. coli ST8346 isolates. The spread appears to be due to independent acquisition events. We identified the putative origins of these plasmids and detected a possible recombination event in a novel IncA/C plasmid. These findings emphasize the importance of ongoing surveillance and further investigations.