Synergy Between Two Chimeric Lysins to Kill Streptococcus pneumoniae.

Roberto Vázquez,Pedro García

doi:10.3389/fmicb.2019.01251

Abstract

Phage lysins constitute a new generation of antimicrobials that are becoming a promising alternative and complementation to current antibiotic therapies, which are nowadays called into question by the increasing numbers of multiresistant bacteria. Streptococcus pneumoniae is a leading human pathogen causing serious infectious diseases in children and adults. Within the host-parasite interplay system of pneumococcus and its phages, several antipneumococcal lysins have been described and, among them, chimeric lysins Cpl-711 and PL3 stand out for their potent bactericidal activities. Here, evidence is presented on the synergistic cooperation of the catalytically diverse lysins Cpl-711 and PL3 in different assays, like purified cell wall enzymatic degradation, in vitro bacterial cell growth inhibition, and killing of both planktonic and biofilm grown cells. Synergy between Cpl-711 and PL3 has been shown to reduce the amount of enzyme necessary to inhibit growth in checkerboard assays with a sum of fractional inhibitory concentrations ≤0.5 for all pneumococcal strains tested, while also significatively increasing bactericidal effect by ≥2 logs with respect to the sum of activities of Cpl-711 and PL3 individual treatments. Moreover, the combination of these two lysins showed synergy in an adult zebrafish model of pneumococcal infection. This study consolidates the possibility of formulating highly efficient and synergistic antibacterial enzymes that could improve our ability to fight multiresistant bacterial infections.

Highlights

Interest in developing novel ways of treating infectious diseases is currently growing due to the worrisome reports on the increase of multidrug resistant (MDR) bacterial strains (Tacconelli et al, 2018), which threatens to hinder our ability to successfully treat bacterial infections with our current antibiotic-based therapies
To test the possible synergy between two different lysins we chose the most promising ones in terms of Minimal Inhibitory Concentration (MIC) and bactericidal activity, i.e., the lysozyme Cpl-711 and the NAMamidase PL3. These two enzymes were tested using purified pneumococcal cell walls labeled with Remazol Brilliant Blue (RBB) and spectrophotometrically measuring the degradation products
The possible therapeutic use of lysins would be focused against certain bacterial pathogens that pose high resistance levels against the common antibiotics of choice

Summary

Introduction

Interest in developing novel ways of treating infectious diseases is currently growing due to the worrisome reports on the increase of multidrug resistant (MDR) bacterial strains (Tacconelli et al, 2018), which threatens to hinder our ability to successfully treat bacterial infections with our current antibiotic-based therapies These so-called “superbugs” seem an outcome of the selective pressure exerted by human use and abuse of antibiotics, in human healthcare settings and in farming and food production industries (O’Neill, 2016). Phage lysins ( referred to as “endolysins” or “enzybiotics”) are enzymes that break specific bonds of bacterial peptidoglycan and allow the release of mature virion particles from host cells leading to cell lysis and death These enzymes are being repurposed for Synergy Between Lysins to Kill Pneumococci bacterial killing from outside the cell. The intrinsic killing activity of phage lysins can even be improved by engineering the wild type enzymes (São-José, 2018) and/or combining them with other lysins, antibiotics or certain compounds to get a synergistic effect (Letrado et al, 2018)

Methods

Results

Discussion

Conclusion