Escherichia coli, E. coli, is the Dr. Jekyll and Mr. Hyde of the microbe world. A member of the Proteobacteria group of fecal microbes, alongside Salmonella, Campylobacter, Klebsiella and other potential pathogens, E. coli can be your friend, protecting you from diarrheal diseases such as cholera and dysentery. Or it can be your greatest enemy responsible for intestinal inflammation, urinary tract infections, sepsis, and adding to risk for colon and breast cancer, autoimmune diseases, neurodegenerative diseases, and diverticular disease.

An example that illustrates E. coli‘s good side was made in 1917 by German physician, Dr. Alfred Nissle, who observed that soldiers fighting in the muddy trenches of the First
World War would suffer severe diarrheal diseases contracted by contact with infected feces, diseases such as dysentery caused by Shigella, causing the death of many due to dehydration. But there was one German soldier who seemed oddly impervious. Dr. Nissle examined the stool of this one soldier and (incredibly for the time) isolated a microbe, a strain of E. coli that came to be known as E. coli Nissle 1917 that, when administered to others, prevented infectious diarrheas caused by exposure to Salmonella and Shigella. This E. coli strain also enhanced the immune response (e.g., increased anti-inflammatory IL-10 levels) and strengthened the intestinal barrier. To this day, this microbial strain is sold as a probiotic in Europe as a product called “Mutaflor,” along with a few other E. coli strains. Subsequent research with this strain of E. coli has also revealed that it can sometimes induce remission of ulcerative colitis, Crohn’s disease, irritable bowel syndrome, and necrotizing enterocolitis, suggesting that, if a beneficial strain can “outmuscle” pathogenic related species/strains, dramatic improvements in bowel health can be experienced. More recent research has demonstrated that the difference between “good” and “bad” E. coli is a single gene, the clbA gene. (Given the ability of this microbe to “switch” back and forth between harmless to harmful, there has been understandable reluctance to embrace the Nissle 1917 strain as a probiotic in the U.S.)

Unfortunately, there are many examples of the havoc other E. coli strains can wreak on human life. Many people have died, for instance, from consumption of lettuce contaminated by strains of E. coli originating from contamination by cow manure. Shiga toxin-producing E. coli O157 can cause a condition called hemolytic uremic syndrome that can result in kidney failure and death. E. coli is also the dominant species in most cases of small intestinal bacterial overgrowth, SIBO. E. coli is also responsible for 80% of all urinary tract infections: bladder, kidneys (pyelonephritis), and sepsis that can be catastrophic. E. coli contamination of restaurant food from human fecal material is among the most common causes of food poisoning resulting in diarrhea, sometimes bloody, vomiting, and occasionally more serious illness, outbreaks tracked by the CDC.

This two-faced aspect of E. coli raises some bigger questions. If this microbe is, on the whole, bad for human health and there are numerous other examples of species within the broader Proteobacteria category, can’t we just eradicate the entire collection and enjoy improved human health? This question has not been fully answered, but it does appear that some members of this category do provide beneficial effects. Some species of Proteobacteria, for example, consume oxygen, creating a more hospitable environment for obligate anaerobic species, i.e., species that are killed by any exposure to oxygen, to colonize the GI tract. The important features of Proteobacteria like E. coli are therefore 1) numbers (too many is not good), 2) context (i.e., the composition of microbes they keep company with), and 3) location, i.e., gaining added pathogenic potential when these species gain access to the small intestine, stomach, and other body organs.

A member of my had a stool analysis run that showed complete absence of E. coli. He asked if there was something he should do about this and I told him that I didn’t know, but I did inform him about the availability of the probiotic E. coli, Mutaflor. He therefore decided to obtain the probiotic and make yogurt out of it to increase microbial counts. He reported—surprisingly—that it made a delicious yogurt (that I called “Poo Yogurt”) and that consuming it increased his sense of well-being and reduced some abdominal symptoms he was experiencing.

Gaining insights into the roles for this and other microbes is an ongoing and evolving effort. E. coli is vastly outnumbered by other bacterial species in the GI tract (it’s not even in the top 50 most plentiful microbes). Despite representing a minority of the microbes in the human GI tract, E. coli appears to play an outsized role in human health and disease. If you are among the majority of people who lack this strain of E. coli, or related strains that “antagonize” species like Shigella or Salmonella, or if you have ulcerative colitis, should you add this microbe to your list of probiotics or ferments? I’m not sure, but add this microbe to the list of those to consider in such situations.