Mike the Mad Biologist

A Commensal ‘Epidemic’ in E. coli?

It sure looks that way. Last night, I was talking to a colleague and he told me that several groups, including his, are seeing a very interesting pattern in commensal Escherichia coli (those E. coli that live in everyone’s gut and aren’t making us sick).

In humans, it appears that roughly 20% of all commensal E. coli belong to one of three clones that have a global distribution (in bacteriology, a clone is a group of very closely related strains). (an aside: In animals, there doesn’t appear to be this skewed pattern. In animals, the distribution of clones appears to be more evenly distributed, with no predominant clones.)

This is interesting because we see the same pattern of epidemic spread with pathogenic (disease-causing) bacteria in humans. With methicillin resistant Staphylococcus aureus (MRSA), there are often a few predominant clones (or even one) that is extremely common. The rise of vancomycin resistant enterococci (VRE) in Europe was largely due to the spread of one clonal type (frighteningly, it appears that an identical pattern of VRE spread is beginning to repeat itself in the U.S. And we do nothing).

So it looks like there’s something about human populations that predisposes human microbial fauna towards a pattern of epidemic spread, even when the bacterium isn’t causing any disease. Hopefully, as the cost of molecular epidemiology decreases, we’ll be able to determine whether this pattern holds up. Since so many species of bacteria that cause disease are often commensals, and not ‘strict’ pathogens (e.g., S. aureus, Enterococcus, Streptococcus pneumoniae, and E. coli), we really need to focus more of our efforts on understanding the biology of the commensal strains of ‘pathogenic’ bacteria, especially since the commensals are the majority in these species.

Comments

  1. #1 Steven
    March 1, 2007

    Cool. I am doing a degree in Microbiology and we have just finished lectures on micobial interactions. Mutualism, Commensialism, Cooperation, Cross-feeding etc.

  2. #2 Dan Stoebel
    March 2, 2007

    Mike, I think you’ve been hanging out with MDs for too long. I assume that your aside should have read “In non-human animals”

    Has anything been published yet?

  3. #3 Mike the Mad Biologist
    March 2, 2007

    Dan,

    heh heh (although that was actually someone else’s phrase & we both know said someone). Hasn’t really been published yet (maybe by the end of the year…)

    Steven,

    thanks. As far as I can tell, you, DS (above), and Carl Zimmer are the only ones who read the post;)

  4. #4 Steven
    March 2, 2007

    Haha. Your welcome.

  5. #5 Steven
    March 2, 2007

    Carl Zimmer? Think I just bought his book. Evoluition: Triumph of an idea from Darwin to DNA.

  6. #6 crfullmoon
    March 3, 2007

    …”In” (non-human) “animals, there doesn’t appear to be this skewed pattern”…

    Animals studied are still eating a more “natural” diet?
    Perhaps there are some additions to human internal or external environment
    that are helping drive what strains do best in us?

  7. #7 Paul Orwin
    March 3, 2007

    I read this stuff too!
    On the note of epidemic spread of enterics, it seems the best likely candidate explanation is that animals eat a lot of food mixed with their own feces and those of other animals, whereas people tend to avoid that? I’m assuming that the animal pops in question were farm or ranch animals, not wild? Interesting – I wonder if the pattern holds for all gut microbes or only some…

  8. #8 Thinlina
    March 3, 2007

    It would be interesting to know if people in countries where is a dominant culture of large mass production food/meal companies, are more inclined to have only a few predominant clones of flora strains than people in countries where more diverse food production chain.

    Also the antibiotics used in modern world are not so very diverse.
    - For bacters: betalactams, tetracyclines, macrolids, clindamycin, metronidazole, fluorokinolons, sulphonamide and trimetoprime. Glykopeptides, aminoglycosides, quinine alkaloids.
    - For viruses: nucleosides, adamantanes, neuraminidase inhibitors, interferons (made in e.coli!).
    - For fungi: allyle amines, azoles, polyens and ekinocandine

    It isn’t a complete list, but there are some twenty or thirty different kinds of antibiotica that are used in our modern world. And how many different kinds of microbes in our guts?

  9. #9 Thinlina
    March 3, 2007

    Paul,
    “On the note of epidemic spread of enterics, it seems the best likely candidate explanation is that animals eat a lot of food mixed with their own feces and those of other animals, whereas people tend to avoid that?”

    Based only on subjective observations of small children, they tend to put almost everything on hand to their mouths :)

  10. #10 Toaster Sunshine
    March 3, 2007

    Would this perhaps have something to do with how little variation there is in the genomes of humans? I remember reading somewhere that a large tribe of chimpanzees harbors more genetic diversity than the entire human race, and from what I understand of anthropology, the evidence suggests that all modern humans are descended from a very small group of ancestors. Given that the human stomach is really good at killing bacteria, perhaps food sources of gut bacteria can be ruled out. So perhaps the fetus isn’t as sterile as we thought, and perhaps gut bacteria are also handed down directly instead of environmentally acquired.

  11. #11 Paul Orwin
    March 5, 2007

    Thinlina,
    Quite right. I should clarify-even though children do that, they are primarily exposed to the fecal bacteria from their family, preserving the essentially vertical transmission of the organisms. There are other issues here, but this seems like it could be worth checking.

  12. #12 Bank zdjec
    August 17, 2007

    I’m assuming that the animal pops in question were farm or ranch animals, not wild? Interesting – I wonder if the pattern holds for all gut microbes or only some…

  13. #13 Artikelverzeichnis
    October 11, 2007

    Thank You for another very interesting article. Itís really good written and I fully agree with You on main issue, btw. I must say that I really enjoyed reading all of Your posts. Itís interesting to read ideas, and observations from someone elseís point of viewÖ it makes you think more. So please try to keep up the great work all the time. Greetings

  14. #14 yellowpages
    November 13, 2007

    Wonderful Article i enjoyed reading it, thanks for sharing with us!

  15. #15 christmas gifts
    December 11, 2007

    Very interesting indeed. It appears Biology has come a long way. To think none of these discoveries could have been made if it wasn’t for the simple microscope.
    I’d be interested in knowing if the study was conducted over farm animals, or wild animals. That might make a difference. I’m not sure where that would place us as humans, though, especially if wild animals have a closer resemblance to us in this arena. He he…

  16. #16 sharp aquos
    December 19, 2007

    Cool. I am doing a degree in Microbiology and we have just finished lectures on micobial interactions. Mutualism, Commensialism, Cooperation, Cross-feeding etc.

  17. #17 Aristo
    December 30, 2007

    Thank You for another very interesting article. Itís really good written and I fully agree with You on main issue, btw. I must say that I really enjoyed reading all of Your posts. Itís interesting to read ideas, and observations from someone elseís point of viewÖ it makes you think more. So please try to keep up the great work all the time. Greetings

  18. #18 kral oyun
    January 4, 2008

    Itís very good article Thanks

  19. #19 Skulpturen
    January 10, 2008

    There are many useful informations in this article. Thanks and greetings from Thuringia!

  20. #20 Springerle Molds
    January 18, 2008

    Good stuff. Thanks and greetings!

  21. #21 custom pet portraits
    February 5, 2008

    This reminds me of one of the findings we made way back in college when we were doing our undergraduate thesis on probiotics. We have observed the same situations when we were studying effects of our sample on E. coli.

  22. #22 Dekoration
    February 21, 2008

    Thanks for this really useful article.Great cheat sheet, I appreciate it very much.

  23. #23 bilard
    May 23, 2008

    Great and excellent article itís realy helpful. Thanks again.

  24. #24 mirc
    March 25, 2009

    thanks

The site is undergoing maintenance presently. Commenting has been disabled. Please check back later!