16 Oct 2014

Ninja Viruses

From Our Changing World, 9:06 pm on 16 October 2014

By Veronika Meduna Veronika.Meduna@radionz.co.nz

Earlier this year, the World Health Organization issued a report, warning that antibiotic resistance is a serious threat to public health and that without urgent action “the world is headed for a post-antibiotic era, in which common infections and minor injuries which have been treatable for decades can once again kill”.

Massey University biologist Heather Hendrickson argues that as we reach peak antibiotics, we should consider another way of treating bacterial infections with viruses known as bacteriophages.

Heather Hendrickson's (centre, with headphones) team at Massey University. Eli Christian and Jess Fitch, who feature in this podcast, are on the left.

Heather Hendrickson's (centre, with headphones) team at Massey University. Eli Christian and Jess Fitch, who feature in this podcast, are on the left. Photo: Heather Hendrickson

Bacteriophages, or phages for short, are ubiquitous in the environment and they are already part of our bodies’ first line of attack. Heather says the biggest advantage phages have over broadband antibiotics, which will kill both pathogenic and beneficial bacteria, is that each virus specialises in infecting and destroying specific bacterial strains.

If you think about dropping an antibiotic into an organism as destroying so many things that it’s almost like a nuclear bomb, then what we have in bacteriophages, potentially, is something that’s more like a ninja. It’s only going to go in and kill the things that we’re worried about and that make us sick.'

Heather’s team has been scouring the environment for bacteriophages, focusing on those that target a harmless bacterium called Pseudomonas fluorescens. Pseudomonas is a group of common and harmless soil bacteria, but it also includes pathogenic strains such as Psa (Pseudomonas syringae pv actinidiae) which affects kiwifruit.

Regardless of whether a bacterium is beneficial or harmful, there will be a phage specific to it. “This is a dynamic in nature that always exists. One of the things that we’re hoping is that’s a dynamic that we can find ways of utilising to our own benefit as humans.”  

Meet Skullduggery, Fabio and Noxifer, the jumbo phages discovered during the Hendrickson lab's phage hunt.

Meet Skullduggery, Fabio and Noxifer, the jumbo phages discovered during the Hendrickson lab's phage hunt. Photo: Heather Hendrickson

In this podcast (audio below), students Jess Fitch and Eli Christian explain how they extract phages from a soil sample and how they characterise each of them with the help of DNA sequencing and microscopy. One of the unexpected results from the team’s phage hunt was that they found several new jumbo phages, which look like a cross between a space ship and a spider. They are significantly bigger than normal phages and have 200 to 400 genes, 10 times more than expected.  

Like any virus, bacteriophages have to attack a cell to reproduce, so they are not considered to be alive. “They are inert. They are basically protein shells with DNA inside. The most interesting ones we found are very large shells with a very long sheath, and possibly legs on the end of that spike. These legs attach to the target cell, then inject the phage DNA into the bacterium.”

Bacteriophages are already used in the fish, cheese and kiwifruit industries to target pathogens. In the past, they have also been used in humans as a treatment against infections, but are now not approved in any kind of human use.

“One of the things that I’m really hoping is that as people learn more about viruses they will be more willing to consider phages as a real tool in our arsenal. As we are running out of potential  in terms of antibiotics, we need to start thinking about creative ways of killing the bacteria that are harming us without killing the bacteria that are not harming us.”

Most bacteria in the environment are beneficial and Heather says bacteriophages have already evolved to specifically target the few bacteria that are harmful to us. They are already part of our immune system, and found in large quantities in any kind of mucus, such as snot.

“It is going to take a major change in the way that policy makers and the public think to start integrating these viruses that are already really all over us. They recycle themselves, they amplify where they are needed, they make more copies of themselves where they find their target organisms – in many ways, there are a great way forward in terms of thinking about the pathogens that we need to find new ways of dealing with.”

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