Potential for Bacteriophage Endolysins to Supplement or Replace Antibiotics in Food Production and Clinical Care

Abstract

There is growing concern about the emergence of bacterial strains showing resistance to all classes of antibiotics commonly used in human medicine. Despite the broad range of available antibiotics, bacterial resistance has been identified for every antimicrobial drug developed to date. Alarmingly, there is also an increasing prevalence of multidrug-resistant bacterial strains, rendering some patients effectively untreatable. Therefore, there is an urgent need to develop alternatives to conventional antibiotics for use in the treatment of both humans and food-producing animals. Bacteriophage-encoded lytic enzymes (endolysins), which degrade the cell wall of the bacterial host to release progeny virions, are potential alternatives to antibiotics. Preliminary studies show that endolysins can disrupt the cell wall when applied exogenously, though this has so far proven more effective in Gram-positive bacteria compared with Gram-negative bacteria. Their potential for development is furthered by the prospect of bioengineering, and aided by the modular domain structure of many endolysins, which separates the binding and catalytic activities into distinct subunits. These subunits can be rearranged to create novel, chimeric enzymes with optimized functionality. Furthermore, there is evidence that the development of resistance to these enzymes may be more difficult compared with conventional antibiotics due to their targeting of highly conserved bonds.

TSPphg Lysin from the Extremophilic Thermus Bacteriophage TSP4 as a Potential Antimicrobial Agent against Both Gram-Negative and Gram-Positive Pathogenic Bacteria

“…All ORF predictions were refined by blasting ORFs to the NCBI database. The conserved domain analysis was carried out based on the NCBI Conserved Domain Database Viruses 2020, 12,192 3 of 12 (CDD v3.17, last update: 2019-04-03). This genome project has been deposited in GenBank under the accession number MH992131.1.…”

“…Briefly, the bacteria were grown at 37 • C in a rotary shaker at 150 rpm until an OD 600 of 0.6-0.8 was reached, then centrifuged at 1000 g for 10 min at 4 • C, washed twice, and resuspended in PBS containing 137 mM NaCl, 2.7 mM KCl, 4.3 mM Na 2 HPO 4 , and 1.4 mM KH 2 PO 4 at a pH of 7.4. For time-kill curve experiments, approximately 10 7 CFU/mL of bacterial cells were treated with increasing concentrations of TSPphg (17,34, and 68 µg/mL) in PBS (pH 7.4) Viruses 2020, 12,192 4 of 12 that was chosen based on an analysis of the effects of different pH values and NaCl concentrations on the activity of TSPphg. After incubation at 37 • C and 150 rpm for 0 to 90 min (samples were taken at an interval of 10 min), aliquots were serially diluted and spread onto LB agar plates.…”

“…Viruses 2020, 12,192 6 of 12 activity after a 30 min heat treatment between 40 and 70 °C, suggesting its resistance to denaturation at high temperatures.…”

“…It is well known that K. pneumoniae is a common cause of severe infections including pneumonia, endophthalmitis and meningitis [25]. Because of its hypervirulence and general occurrence of resistance Viruses 2020, 12,192 7 of 12 to most antibiotics, in recent years infections caused by K. pneumoniae have become progressively difficult to treat [26,27]. In this study, we examined the antibacterial activity of TSPphg against nine different antibiotic-resistant strains of K. pneumoniae that are exceedingly hard to deal with in clinic practice.…”

In vitro and in vivo efficacy of combinations of colistin and different endolysins against clinical strains of multi-drug resistant pathogens

“…There are no reports of bacteria developing resistance to endolysins, which is a problem in both antibiotic therapy and phage therapy 16 . Moreover, endolysins have been recognized in the US "National Action Plan for Combating Antibiotic-resistant Bacteria" 24 , which identified the use of "phage-derived lysins to kill specific bacteria while preserving the microbiota" as a key strategy to reduce the development of antimicrobial resistance due to www.nature.com/scientificreports www.nature.com/scientificreports/ the absence of toxicity in human cells 25,26 . Moreover, some endolysins have been found to display activity against sub-populations of microbes 27,28 extracted from biofilm [29][30][31] and to be useful in other innovative treatments.…”