Biology and Genomics of an Historic Therapeutic Escherichia coli Bacteriophage Collection

Abstract

We have performed microbiological and genomic characterization of an historic collection of nine bacteriophages, specifically infecting a K1 E. coli O18:K1:H7 ColV+ strain. These phages were isolated from sewage and tested for their efficacy in vivo for the treatment of systemic E. coli infection in a mouse infection model by Smith and Huggins (1982). The aim of the study was to identify common microbiological and genomic characteristics, which co-relate to the performance of these phages in in vivo study. These features will allow an informed selection of phages for use as therapeutic agents. Transmission electron microscopy showed that six of the nine phages were Podoviridae and the remaining three were Siphoviridae. The four best performing phages in vivo belonged to the Podoviridae family. In vitro, these phages exhibited very short latent and rise periods in our study. In agreement with their microbiological profiles, characterization by genome sequencing showed that all six podoviruses belong to the Autographivirinae subfamily. Of these, four were isolates of the same species (99% identity), whereas two had divergent genomes compared to other podoviruses. The Siphoviridae phages, which were moderate to poor performers in vivo, exhibited longer latent and rise periods in vitro. Two of the three siphoviruses were closely related to each other (99% identity), but all can be associated with the Guernseyvirinae subfamily. Genome sequence comparison of both types of phages showed that a gene encoding for DNA-dependent RNA polymerase was only present in phages with faster replication cycle, which may account for their better performance in vivo. These data define a combination of microbiological, genomic and in vivo characteristics which allow a more rational evaluation of the original in vivo data and pave the way for the selection of phages for future phage therapy trails.

Characterization of a Lytic Bacteriophage as an Antimicrobial Agent for Biocontrol of Shiga Toxin-Producing Escherichia coli O145 Strains

“…Three consecutive ORFs in Ro145clw (ORF_51, ORF_52, and ORF_53) coded for putative holin-like class II, holin-like class I, and endolysin, respectively, were associated with forming a holin-dependent host cell lysis system [20]. Both ORF_51 and ORF_52 shared 92% and 95% average nucleotide identity, respectively, with their counterparts in phage G AB-2017, whereas ORF_53 shared 86% average nucleotide identity to the gene encoding lysozyme in Escherichia phage P AB-2017 [21]. Two spanin proteins encoded by ORF_66 and ORF_67 were located downstream of the cell lysis system in the Ro145clw genome and were associated with the final step of cell lysis by breaking the structure of the outer membrane of the host cell to release the phage progenies [22].…”

In-Gel Isolation and Characterization of Large (and Other) Phages

“…However, we know of no example of a jumbo phage or near-jumbo phage that behaves as a smaller, T3/T7-like podophage in a plaque diameter vs. A screen. Usefulness of this screen is suggested by the observation that lytic podophages are found dominant in phage cocktails successful in treating of E. coli bacteremias [45].…”

In Vitro Characteristics of Phages to Guide ‘Real Life’ Phage Therapy Suitability

“…While the isolation of phages has been a continuous and ongoing effort of phage biologists globally [ 21 , 22 , 23 , 24 , 25 ], it should be noted that considerable collections of phages that have the potential for therapeutic trialing and application, exist. One such collection of nine E. coli phages has recently been assessed to identify the common microbiological and genomic characteristics of phage isolates exhibiting therapeutic potential in vivo [ 26 ]. This historic collection of E. coli O18:K1:H7 phages was characterized as being comprised of six Podoviridae phages and three Siphoviridae phages.…”