Dr Oleksandra (Alex) Rudenko

As a microbiologist, Alex is all too familiar with the threat of AMR. Her work on a vaccine to prevent lactococcosis in trout could help to curb AMR by reducing the need for antibiotics in aquaculture.

Q. How did you become involved in vaccine research?

Alex: I’ve been fascinated with biology since I was a kid. After I got my master’s degree in microbiology in Western Ukraine, I worked in a clinical diagnostics lab. But I wanted to get back to scientific research. I came to Australia to do my PhD at the University of Queensland and never left.

Previously I developed a trivalent vaccine against three major bacterial pathogens in yellowtail kingfish. Now I’m working on a vaccine against Lactococcus garvieae, which causes lactococcosis in rainbow trout.

Q. Why are vaccines important in the fight against AMR?

Alex: Effective vaccines negate the need for antibiotics. As vaccinated animals don't get the disease, they don’t need to be treated with antimicrobials. And the preventive use of antimicrobials isn’t required either.

Q. What does your work on the SAAFE trout vaccine project involve?

Alex: We receive bacterial isolates from trout farms across Australia – they send us samples from sick fish. We sequence the bacterial genomes to identify genetic regions encoding antigens that could be used in vaccines. We also compare the genomes from different isolates, track the evolution of the bacteria, and look for the emergence and spread of AMR genes.

All that information gives us ideas of how to improve the L. garvieae vaccines that are currently in use. They’re not 100% effective, so there’s huge room for improvement.

I make the vaccines in the lab and then test them in the aquarium. We keep around 500 fish in three circular 1000 L tanks in an 8 ton recirculating system. We grow them up, tag them so we can test different vaccines in the same environment or tank, and vaccinate them. It takes around two months after vaccination before the fish reach the peak of their primary immune response. When they’re ready, we challenge them with the bacteria and watch for the vaccine’s protective effect. Usually within a week, we have a result.

Q. What part of your current work is the most challenging?

Alex: Anyone who runs experimental trials with animals knows how unpredictable they can be. Everything needs to be perfect; any change to the conditions can confound the results. So the fish kind of become my babies for a few months. It’s a big investment to run these trials, and the fish become more and more valuable with each day. They’re very precious.

Q. What have you discovered so far in the project?

Alex: At first, we thought that the variation in vaccine efficacy was due to differences between bacterial strains. That's the funny thing about working with bacteria – it's very much about the strain. You think you know a species, but it can have so much variety. When we sequenced more than 100 bacterial genomes from across Australia, we found they are very similar. But these strains are very different from strains in other countries. That was unexpected.

Based on the results of our first trial, we think we’ve identified a better approach. We’ll trial the next version of the vaccine in a few months.

We have big hopes for an effective vaccine. It would contribute to the reduction of AMR, but the immediate benefit will be for trout farmers in Australia. They really need an improved vaccine to stop fish losses from lactococcosis.