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Saturday, 23 April 2016

E. coli: the 'E' isn't for 'Evil'

It actually stands for 'escherichia' (which doesn't exactly roll off the tongue, hence always just being called E coli).

Yesterday I was reading something about superbugs, and it listed E coli as one of the deadly ones. Everyone's always on the lookout for E coli contamination in food, restaurants, bathrooms etc. But is it really as scary as it's portrayed in the media?

Some strains are, definitely. K2 causes meningitis in newborn babies, O104H4 causes pretty nasty kidney damage (an outbreak in 2011 killed 52 people across the world) and scarily-named 'Entero-haemorrhagic E coli' strains like O157 cause bloody diarrhoea. Obviously being infected by any of these are on nobody's to-do-list, but just as the majority of bacteria as a whole don't cause disease, there are a huge range of E coli strains that aren't a threat at all. In fact, pretty much everyone has E coli as part of their normal community of gut bacteria! Animals included. That's partly why it's always looked for in restaurants and stuff; if it's in the intestines, then it'll be in what exits the intestines... so when they say 'we found E coli in 4/5 restaurants' they're basically saying there's faeces all over the place, so you should probably eat somewhere else until they start washing their hands! E coli  is therefore the poster boy for faecal contamination, but it's often more of a sign of contamination rather than the worst bacteria in there. It's just that it's much easier to  grow in the lab to detect, and that nowadays when there's so much genetic screening it's again easy to look for as we've got the whole genome sequenced. Often, food poisoning bacteria like Campylobacter jejuni are much more picky about what they want to grow on in the lab so it's quicker, cheaper and easier to just look for the E coli.

This is where E coli starts to redeem itself though; because it's so happy in lab conditions, it's really easy to work with! Everybody should love E coli. Not only is it easy to grow, it's pretty easy to insert genes into via various methods so we can customise it to be useful for all sorts of applications. One of the first examples of this, and one of my favourite examples of Friendly Bacteria, is the E coli that have been modified to produce human insulin. They first did this back in the seventies, and insulin is still made in this way to this day! Yeast is used sometimes too. Before that, they had to cut it out of corpses, or from pigs (which needed lots of accompanying medication).

I couldn't list all the ways E coli is used; a quick search for it on Google Scholar gives more than two and a half million different research papers using it! It's fair to say that without E coli we'd all be a lot worse off.

So should we fear E coli? No! It's our friend! (Apart from the baby-meningitis/bloody diarrhoea ones, feel free to fear them as much as you like)

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