Antibacterial Activity of Peptide Derivatives of Phosphinothricin against Multidrug-Resistant Klebsiella pneumoniae

Abstract

The fast spread of bacteria that are resistant to many classes of antibiotics (multidrug resistant) is a global threat to human and animal health with a worrisome scenario ahead. Novel therapeutical strategies are of crucial importance to combat this phenomenon. For this purpose, we investigated the antimicrobial properties of the naturally occurring tripeptide Bialaphos and a dipeptide L-leucyl-L-phosphinoithricin, the synthesis and diastereomers separation of which are herein described. We demonstrate that these compounds are effective on clinical isolates of the human pathogen Klebsiella pneumoniae, causing hospital-acquired and community-acquired infections. The tested isolates were remarkable for their resistance to more than 20 commercial antibiotics of different classes. Based on previous literature data and our experiments consisting of glutamine supplementation, we suggest that both compounds release phosphinothricin—a well-known nanomolar inhibitor of glutamine synthetase—after their penetration in the bacterial cells; and, in this way, exert their antibacterial effect by negatively affecting nitrogen assimilation in this pathogen.

A Desmethylphosphinothricin Dipeptide Derivative Effectively Inhibits Escherichia coli and Bacillus subtilis Growth

“…Our data suggest that the incorporation of Glu-γ-P H in a dipeptide significantly improves the penetration of the molecule, thus enhancing its antibacterial activity and potential use for treating bacterial infections caused by different microorganisms. This work represents additional evidence that phosphinic compounds can be regarded as interesting molecules with antibacterial activity, as recently proposed for the PT-derived dipeptide on multidrug resistant clinical isolates of K. pneumoniae [14].…”

“…The synthesis, proceeded by the condensation of N-hydroxysuccinimide ester of the N-Cbz-L-Leu (N-Cbz-L-Leu-OSu) with Glu-γ-P H or Glu-γ-P 5 in a water/1,2-dimethoxyethane mixture in the presence of NaHCO 3 /Na 2 CO 3 , was followed by the one-pot removal of the Cbz-protecting group with HBr/AcOH (Scheme 1). Each dipeptide was isolated by ion-exchange chromatography on a sulfocationite Dowex-50W-X8 (H + -form), eluting the resin with a large volume of water; however, the water elution did not allow for the separation of the diastereomeric dipeptides, in contrast to what was obtained with L-Leu-PT [14]. L-Leu-D,L-Glu-γ-P H was obtained with a 76% overall yield, while the L-Leu-D,L-Glu-γ-P 5 had a 54% overall yield; thus, compared with the Glu-γ-P 5 , the H-phosphinic Glu-γ-P H proved to be more reactive.…”

“…All these technical differences and the more stable readings performed in the Varioskan Lux microplate reader explain why this growth behaviour, shown in Figure 2, had originally escaped observation. The two newly synthesized L-Leu-D,L dipeptides, as well as the previously synthesized L-Leu-D,L-PT [14], were tested for their antibacterial activity on E. coli. At this stage of our study we decided not to separate the L-L and L-D diastereomers because natural and phosphorous-containing dipeptides having one or more D-residues are known to be poorly accumulated by E. coli due to a stereochemical preference of Dpp for dipeptides containing L-residues [25,26].…”

“…Hence, PT and the PT-containing tripeptides, Bialaphos or Phosalacine (i.e., PT-L-alanyl-L-leucine-), exhibit strong herbicidal activity [3,5,12,13]. In addition to the well-established herbicidal effect, Bialaphos and a PT-containing dipeptide, L-Leu-L-PT, were remarkably effective in clinical isolates of Klebsiella pneumoniae, which displayed resistance to more than 20 commercial antibiotics belonging to different classes [14].…”

Exploitation of microbial activities at low pH to enhance planetary health

“…A recent and intriguing example includes a study on multidrug resistant K. pneumoniae strains (i.e. resistant to > 10 different antibiotics), isolated from patients, that were inhibited by peptides derived from phosphinothricin (Demiankova et al 2023 ). This work also highlights that “repositioning” of some drugs can be an effective strategy.…”