Research Article: In vitro characterization of PlyE146, a novel phage lysin that targets Gram-negative bacteria

Date Published: February 6, 2018

Publisher: Public Library of Science

Author(s): Yu Larpin, Frank Oechslin, Philippe Moreillon, Grégory Resch, José Manuel Entenza, Stefano Mancini, Jose Melo-Cristino.


The recent rise of multidrug-resistant Gram-negative bacteria represents a serious threat to public health and makes the search for novel effective alternatives to antibiotics a compelling need. Bacteriophage (Phage) lysins are enzymes that hydrolyze the cell wall of bacteria and represent a promising alternative to tackle this ever-increasing problem. Despite their use is believed to be restricted to Gram-positive bacteria, recent findings have shown that they can also be used against Gram-negative bacteria. By using a phage genome-based screening approach, we identified and characterized a novel lysin, PlyE146, encoded by an Escherichia coli prophage and with a predicted molecular mass of ca. 17 kDa. PlyE146 is composed of a C-terminal cationic peptide and a N-terminal N-acetylmuramidase domain. Histidine-tagged PlyE146 was overexpressed from a plasmid in Lactococcus lactis NZ9000 and purified by NI-NTA chromatography. PlyE146 exhibited in vitro optimal bactericidal activity against E. coli K12 (3.6 log10 CFU/mL decrease) after 2 h of incubation at 37°C at a concentration of 400 μg/mL in the absence of NaCl and at pH 6.0. Under these conditions, PlyE146 displayed antimicrobial activity towards several other E. coli, Pseudomonas aeruginosa (3 to 3.8-log10 CFU/mL decrease) and Acinetobacter baumannii (4.9 to >5-log10 CFU/mL decrease) strains. Therefore, PlyE146 represents a promising therapeutic agent against E. coli, P. aeruginosa and A. baumannii infections. However, further studies are required to improve the efficacy of PlyE146 under physiological conditions.

Partial Text

The massive use of antibiotics has led to a rise of bacteria that are multidrug-resistant (MDR) [1]. This phenomenon is particularly alarming in Gram-negative bacteria, including Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii, which are responsible for a broad spectrum of infections that could become untreatable [2,3]. The rise of these MDR bacteria and the shortage of novel antibiotics warrants the search and the development of new alternative antibacterial agents [1].

Gram-negative bacteria are becoming increasingly resistant to antibiotics and this poses a problem for the treatment of the associated infections. Due to the shortage of novel antibiotics, innovative strategies must be developed. Lysins are phage-related enzymes that hydrolyze the bacterial peptidoglycan and therefore represent an attractive option to tackle this issue. However, due to the presence of the outer membrane that hinders the access of the lysins to the peptidoglycan of Gram-negative bacteria, lysins have been for long time considered useful only against Gram-positive bacteria. Notwithstanding, recent works have shown that lysins (natural or engineered) do possess antibacterial activity against P. aeruginosa and A. baumannii [8,17,19,20], raising the prospect of a possible use for treating Gram-negative bacterial infections too.




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