Eli5: How is e-coli used as a indicator organism for pathogens like Listeria?

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How does increased levels of ecoli correlate with Listeria?

In: Biology
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I am definitely not an expert on this and my GMP experience was not in food prep… but no one has tried to answer so I will give it a shot.

My understanding of it is that the growth of an indicator species shows that conditions were ideal for a ‘concerning’ microbe to grow. This hints at a defect in the manufacturing process, or a crappy job of keeping things clean in the process.

It’s not that E. coli loves to grow with certain contaminating species, but E. coli probably shares some growth characteristics with the species it is an indicator for (eg. temperatures, concentrations of solutes, etc.), so growth of it alludes to the possibility of growth of one of the concerning bugs.

I can actually answer this! I’m doing a PhD in infectious diseases, particularly with AB toxins.

It turns out that the genetic differences, which is to say how their toxin physically appears, is effectively the same between E. coli, listeria, shiga, and many others. There’s actually some conversation that they’re all the same organism! The reason they cause different diseases is more related to where they infect than with what.

So to answer your question, the toxin these bacteria use are different combinations of the same thing. Like putting a policeman Lego head on a Lego alien body. Since you can look for the same thing, you can use the same test for all of them.