Jeri Barak: breaking a cycle of human/food pathogens in fresh produce

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Jeri Barak, Assistant Professor
Department of Plant Pathology
UW-Madison College of Agricultural and Life Sciences
(608) 890-2581

Healthy-looking produce is likely healthy produce

4:03 – Total time

0:18 – Bacterial research with produce
0:46 – Research progress
1:14 – Types of affected produce
1:33 – How produce is contaminated
2:17 – How bacteria grow on produce
2:51 – Tips for produce buyers
3:26 – Tips for produce growers
3:53 – Lead out


Sevie Kenyon: Jeri, welcome to our microphone! Start out by telling us a little bit about what you work on here.

Jeri Barak: I work on human pathogens, which would include pathogenic e-coli and salmonella enterica, in association with fresh produce. We’re interested in the genes and the mechanisms that allow these human pathogens to colonize our fresh produce, in the hopes that we could find targets for intervention strategies.

Sevie Kenyon: Jeri can you give us a little idea how far along you are with this kind of research?

Jeri Barak: We have identified specific genes and mechanisms that allow salmonella and pathogenic e-coli to colonize these plants and it is our hope that further down the line this research could become transitional and that people could use these targets to reduce the populations and the contaminations on fresh produce.

Sevie Kenyon: Jeri, can you tell us what kind of produce we’re talking about?

Jeri Barak: Alfalfa sprouts, leafy greens, which may include lettuce, spinach and tomato fruits. There have been outbreaks in association with a lot of different types of produce.

Sevie Kenyon: And Jeri can you perhaps describe for us, a little bit about how the bacteria and the produce work?

Jeri Barak: So, it’s our best estimation that the produce becomes contaminated pre-harvest. The most likely routes of contamination may be water, whether it’s irrigation water or water used on the farm or contamination events. If you had flooding, the soil could be contaminated, in which you grow these crops. That’s the most likely route of contamination.  So, that’s how these pathogens reach our fresh produce. They are leaving the farm, possibly already contaminated.

Sevie Kenyon: Jeri, could you perhaps describe the conditions that would be favorable for the growth of these negative bacteria?

Jeri Barak: There are sugars and carbon sources available in the plants and as soon as those nutrients are released, whether they’re released by a plant pathogen damaging the leaves or by someone cutting them or harvesting them, these sugars and nitrogen are released and the bacteria starts to grow. As the bacteria starts to grow, population increases and humans are more likely to become ill from consuming this produce.

Sevie Kenyon: Do you have any tips for people buying fresh produce?

Jeri Barak: the two most important factors is one, buy the healthiest looking produce you can find, and two, treat your fresh produce like you would ice cream – refrigerate it as soon as possible – don’t put it in the car and go run errands, rush it home and put it in your refrigerator. Unfortunately, washing the produce doesn’t help in the contamination by these bacteria, because these bacteria are adhered to the produce in a way that they cannot be washed off.

Sevie Kenyon: are there things that can be done, perhaps, by the growers?

Jeri Barak: the grower can use the best type of agricultural water – irrigation water, pesticide and diluents – perhaps on a large scale, if the irrigation water could be tested. The other thing is to reduce the incidence of plant disease because we know there is an interaction between diseased fresh produce and the population of the human pathogens.