New phage from ‘viral dark matter’

January 6, 2020 0 By FM

An international team based in Austria has unearthed a previously unknown type of virus in samples of human bodily fluids. 

The researchers were looking for bacteriophages that attack the E. coli bacterium (coliphages) found in the human gut. 

Bacteriophages are viruses that infect bacteria. The diversity of bacteriophages still remains obscure in human body biomes, representing a so-called “viral dark matter.”

Only a handful of research teams around the world have looked into phages in humans in spite of their key role in human health. A balance between the various types of bacteria in the body is crucial for health. And phages attack specific bacteria, which could, in turn, throw this equilibrium severely off kilter.

The team identified a total of 43 bacteriophages in samples of human bodily fluids, particularly in blood samples. 

They found phages in almost one in seven samples and a new kind of phage from the Tunavirinae subfamily.

“In this study, we have found a species that is clearly a new one identified,” says Prof Friederike Hilbert of the Department for Farm Animals and Veterinary Public Health at the University of Veterinary Medicine Vienna, who headed the research team. “Another phage species is exactly on the border of a new species. We cannot foresee what will happen in regard to new species descriptions, but for sure more sequence data will be the base to come to a decision,” 

A detailed sequence-based classification and characterization will help to decide if novel phages can be tools for diverse phage applications.

Vehicles of horizontal gene transfer

The discovery of such phages in the human body is especially significant because it had been previously demonstrated that phages have an impact on bacterial pathogenesis by carrying virulence factors, antimicrobial resistance genes, and host adaptation factors.

The study “per se “does not include any clinical data, but there are other studies that have already shown an influence of phages on the severity of clinical bacterial infections e.g. for Pseudomonas aeruginosa, explains Prof. Hilbert.

As important vehicles of horizontal gene transfer, phages contribute significantly to the strain-to-strain differences observed within the same bacterial species. Consequently, information about the prevalence and frequency of phages in humans, as well as the relationships between them, is urgently needed. 

The researchers believe that phages might be a common microorganism in the human body. 

The team also examined the effectiveness of standard hospital disinfectants against the isolated phages and found that not all disinfectants were capable of reliably destroying phages.

The findings have now been published in an international journal Frontiers in Microbiology.