Transcript

INTERVIEWER:

Using one organism to kill another might not seem like such a great idea, but cats do make very good ratters. Scale things down a bit, and we might just be able to use one bacterium to kill another. Shigella is a family of bacteria that causes dysentery, and hundreds of thousands of deaths, mostly children, every year. Now good sanitation prevents Shigella infections, but there is no vaccine that stops it.

Enter Bdellovibrio bacteriovorus. It's another type of bacteria, but crucially, it's a predatory one. It inserts itself inside its victims and then destroys them from within. And a new paper just published shows that Bdellovibrio can be used to cure a Shigella infection, admittedly in zebrafish, but with no apparent side effects.

And because these bacteria attack a wide range of other microbes, this might just be a way of treating the impending antibiotic resistance crisis. Elizabeth Sockett is the woman behind this study. And I asked her how the experiment worked.

ELIZABETH SOCKETT:

The experiment's a real synergy between two labs. So Serge Mostowy's lab could set up experimental infections into zebrafish with the Shigella. And in our experiments, the Shigella were green fluorescent. They're injected into the hind brain of the zebrafish. Normally, they cause a lethal infection and the zebrafish die. What we did was we injected red Bdellovibrio into the same compartment. And we tested whether those red Bdellovibrio or a buffer control could change the infection.

So the great thing about this experiment was we could see live the numbers of red and green bacteria changing inside the patient, who's the zebrafish. We could also measure the survival of the zebrafish 48 hours later, because they normally die of a Shigella infection of that level. And what we saw was that the red Bdellovibrio started to kill the green Shigella inside the zebrafish, and the survival of the zebrafish improved a huge amount.

INTERVIEWER:

So you inject, first of all, you infect the zebrafish with Shigella, which would kill them.

ELIZABETH SOCKETT:

Yes.

INTERVIEWER:

Then you inject--

ELIZABETH SOCKETT:

With the Bdellovibrio.

INTERVIEWER:

And that kills the Shigella.

ELIZABETH SOCKETT:

Yes. And interestingly, in this experiment the Bdellovibrio start killing first the Shigella, but then the immune system of the fish that wasn't coping with the Shigella wakes up and gets a stimulus from this predation. And it comes in and clears up the rest of the Shigella from the infection. So what we think is that the Bdellovibrio is actually releasing some components of the Shigella as it's killing them early on and the immune system is being awakened to the presence of the Shigella. And also the numbers are dropping due to the direct killing by the Bdellovibrio.