Bacteriolytic Potential of Enterococcus Phage iF6 Isolated from “Sextaphag®” Therapeutic Phage Cocktail and Properties of Its Endolysins, Gp82 and Gp84

Abstract

The number of infections caused by antibiotic-resistant strains of bacteria is growing by the year. The pathogenic bacterial species Enterococcus faecalis and Enterococcus faecium are among the high priority candidate targets for the development of new therapeutic antibacterial agents. One of the most promising antibacterial agents are bacteriophages. According to the WHO, two phage-based therapeutic cocktails and two medical drugs based on phage endolysins are currently undergoing clinical trials. In this paper, we describe the virulent bacteriophage iF6 and the properties of two of its endolysins. The chromosome of the iF6 phage is 156,592 bp long and contains two direct terminal repeats, each 2108 bp long. Phylogenetically, iF6 belongs to the Schiekvirus genus, whose representatives are described as phages with a high therapeutic potential. The phage demonstrated a high adsorption rate; about 90% of iF6 virions attached to the host cells within one minute after the phage was added. Two iF6 endolysins were able to lyse enterococci cultures in both logarithmic and stationary growth phases. Especially promising is the HU-Gp84 endolysin; it was active against 77% of enterococci strains tested and remained active even after 1 h incubation at 60 °C. Thus, iF6-like enterococci phages appear to be a promising platform for the selection and development of new candidates for phage therapy.

The virtue of training: extending phage host spectra against vancomycin-resistant Enterococcus faecium strains using the Appelmans method

“…Figure. 4A presents a detailed description of its genome and a comparison with one of its closest relative Enterococcus phage iF6 ( 19 ). Twenty-four tRNAs were predicted on Porthos as well as 194 ORFs, ~35% of which could be functionally annotated.…”

“…Although neglected for a long time, except within the former Soviet Union area, virulent bacteriophages (phages), i.e., viruses that infect and obligatorily lyse bacteria, are nowadays considered worldwide to combat MDR bacteria ( 9 – 11 ). Initial studies on enterococci were directed against E. faecalis and more recently turned toward E. faecium, involving either phage particles ( 12 – 17 ) or phage endolysins ( 18 , 19 ), as well as the combinations of phage and antibiotics ( 20 – 24 ). One successful case of phage therapy was recently reported in an infant suffering from a VREfm intra-abdominal infection ( 25 ).…”

A Genomic Analysis of the Bacillus Bacteriophage Kirovirus kirovense Kirov and Its Ability to Preserve Milk

“…The phage genome termini were identified by sequencing terminal DNA fragments obtained by the method of rapid amplification of genomic ends (RAGE [ 68 ]) as described previously [ 54 , 69 ], with minor modifications. Phage genomic DNA was used for a typical DNA tailing reaction with terminal transferase (New England Biolab, Cat.…”

A review and new perspective on oral bacteriophages: manifestations in the ecology of oral diseases

“…Bothered by resistance to multiple antibiotics, research on E. faecalis -specific phages has yielded promising results, including vB_EfaP_IME199 [ 113 ] and the newly isolated iF6 [ 114 ]. The E. faecalis phages provide a vast array of therapeutic options because of their varieties in morphology, host range, and potential functions.…”

“…Other endolysins, two of iF6, Gp82, and Gp84, could lyse E. faecalis in both logarithmic and stable growth phases. In addition, the ubiquitinated Gp 84 endolysin could lyse 77% of the E. faecalis strains used in the experiment [ 114 ]. The efficacy of lysins, such as IME-EF1 endolysin [ 101 ] and Lys170 [ 102 ], has also been demonstrated in previous experiments.…”