The β-lactams retain a central place in the antibacterial armamentarium. In Gram-negative bacteria, β-lactamase enzymes that hydrolyze the amide bond of the four-membered β-lactam ring are the primary resistance mechanism, with multiple enzymes disseminating on mobile genetic elements across opportunistic pathogens such as Enterobacteriaceae (e.g., Escherichia coli ) and non-fermenting organisms (e.g., Pseudomonas aeruginosa ). β-Lactamases divide into four classes; the active-site serine β-lactamases (classes A, C and D) and the zinc-dependent or metallo-β-lactamases (MBLs; class B). Here we review recent advances in mechanistic understanding of each class, focusing upon how growing numbers of crystal structures, in particular for β-lactam complexes, and methods such as neutron diffraction and molecular simulations, have improved understanding of the biochemistry of β-lactam breakdown. A second focus is β-lactamase interactions with carbapenems, as carbapenem-resistant bacteria are of grave clinical concern and carbapenem-hydrolyzing enzymes such as KPC (class A) NDM (class B) and OXA-48 (class D) are proliferating worldwide. An overview is provided of the changing landscape of β-lactamase inhibitors, exemplified by the introduction to the clinic of combinations of β-lactams with diazabicyclooctanone and cyclic boronate serine β-lactamase inhibitors, and of progress and strategies toward clinically useful MBL inhibitors. Despite the long history of β-lactamase research, we contend that issues including continuing unresolved questions around mechanism; opportunities afforded by new technologies such as serial femtosecond crystallography; the need for new inhibitors, particularly for MBLs; the likely impact of new β-lactam:inhibitor combinations and the continuing clinical importance of β-lactams mean that this remains a rewarding research area.

Positively charged poly(styrene-co-maleimide) extracts functional membrane proteins into nanodiscs, overcoming some limitations of current nanodisc technology.

No abstract

The emergence of antimicrobial resistance (AMR) represents a significant health and economic challenge worldwide. The slow pace of antibacterial discovery necessitates strategies for optimal use of existing agents, including effective diagnostics able to drive informed prescribing; and development of alternative therapeutic strategies that go beyond traditional small-molecule approaches. Thus, the development of novel probes able to target bacteria for detection and killing, and that can pave the way to effective theranostic strategies, is of great importance.Here we demonstrate that metal-free green-emitting fluorescent carbon dots (FCDs) synthesized from glucosamine⋅HCl and m-phenylenediamine, and featuring 2,5-deoxyfructosazine on a robust amorphous core, can label both Grampositive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) bacterial pathogens within 10 minutes of exposure. Moreover, effective killing of Gram-positive and -negative bacteria can be induced by combining FCD treatment with irradiation by LED light in the visible range. Cell-based, electron microscopy and tandem mass tag (TMT) proteomic experiments indicate that FCD administration in combination with LED exposure gives rise to local heating, ROS production, and membrane-and DNA-damage, suggesting multiple routes to FCD-mediated bacterial killing. Our data identify FCDs as materials that combine facile synthesis from low-cost precursors with labeling and light-dependent killing of clinically important bacterial species, and that thus warrant further exploration as the potential bases for novel theranostics.

The emergence of antimicrobial resistance represents a significant health and economic challenge worldwide. The slow pace of antibacterial discovery necessitates strategies for optimal use of existing agents, including effective diagnostics able to drive informed prescribing; and development of alternative therapeutic strategies that go beyond traditional small-molecule approaches. Thus, the development of novel probes able to target bacteria for detection and killing, and that can pave the way to effective theranostic strategies, is of great importance. Here we demonstrate that metal-free green-emitting fluorescent carbon dots (FCDs) synthesized from glucosamine.HCl and m-phenylenediamine, and featuring 2,5-deoxyfructosazine on a robust amorphous core, can label both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) bacterial pathogens within 10 minutes of exposure. Moreover, effective killing of Gram-positive and -negative bacteria can be induced by combining FCD treatment with irradiation by LED light in the visible range. Cell-based, electron microscopy and Tandem Mass Tag (TMT) proteomic experiments indicate that FCD administration in combination with LED exposure gives rise to local heating, ROS production, and membrane- and DNA-damage, suggesting multiple routes to FCD-mediated bacterial killing. Our data identify FCDs as materials that combine facile synthesis from low-cost precursors with labelling and light-dependent killing of clinically important bacterial species, and that thus warrant further exploration as the potential bases for novel theranostics.