Bacteriophage lysins as alternatives to antimicrobial treatment - an ANIHWA ERA-Net project
Bacteriophages, or phages for short, are viruses that infect bacteria. The majority of phages have the capacity to lyse and kill its host bacteria after replicating themselves. Phages are abundant in nature, they are major regulators of bacterial densities, and the genetic variation of phages is huge, many times larger than the variation of bacteria. Phages are more or less host strain specific; some phages can infect only a single strain or clone of bacteria whereas others can infect a large number of strains or even all members of a group of related strains.
When a phage has replicated its genome, expressed the necessary structural proteins, assembled these into new phage particles and packed the genomes into them, it is time to leave the host bacterium. Phages encode enzymes called endolysins that break down the peptidoglycan layer in the cell wall. The end result is that the bacteria lyse when the progeny phages are released.
The main goal of the BLAAT project is to explore the potential of phage endolysins as alternatives to antibiotics in animal production. These phage encoded enzymes are capable of highly specific, efficient and rapid degradation of the peptidoglycan layer in the bacterial cell wall leading to cell lysis and death of the bacterium irrespectively of its physiological state or resistance to antibiotics. Endolysins are produced at a late stage during a normal phage infection but need the help of other proteins to get through the inner membrane and reach the peptidoglycan layer. Since Gram-positive bacteria lack an outer membrane, endolysins applied from the outside will quickly degrade the peptidoglycan and kill the bacteria. Gram-negative bacteria, on the other hand, have a protecting membrane on the outside as well making them refractory to endolysins applied from the outside. Within the BLAAT project, we will elaborate new strategies for development of endolysins with the capacity to lyse Gram-negative bacteria as well.
We will investigate the therapeutic potential of endolysins against the Gram-positive and antibiotic resistant bacterium Staphylococcus aureus (MRSA CC398) as well as the Gram-negative enterotoxigenic Escherichia coli, ETEC. These are bacteria that cause disease in animal husbandry, and show an increasing rate of antibiotic resistance, and as such also represent important zoonotic pathogens. The former is increasingly recognized as an emerging zoonotic pathogen, while ETEC causes a considerable morbidity and mortality in the pre- and post-weaning pigs.
The main activities in this project include: Creating a collection of phages targeting these two important pathogens; rigorous functional and structural analyses of phages in the collection; identification, cloning, detailed analysis and protein engineering of endolysin genes and finally pilot studies to evaluate the antimicrobial activity of endolysin preparations administered to pigs. Click the figure below for more information on project work packages.