What a difference strain can make

In the world of probiotics, i.e., microorganisms that provide benefit to their host such as us, there is something called strain specificity. I know that this sounds like dull, confusing jargon, but stick with me, as this is going to be among the most important emerging issues in overall health.

To illustrate, let’s take the common bacterial Escherichia coli, or E. coli. “Escherichia” designates the genus of bacteria; there are also Escherichia hermanii and Escherichia vulneris, for example: same genus, different species. “Coli” is therefore the species in E. coli.

You and I have strains of E. coli in our intestines that quietly coexist with us (though it is among the species that proliferates when small intestinal bacterial overgrowth, or SIBO, develops.) But get exposed to say, the O157:H7 E. coli strain from lettuce contaminated with cow manure, and you develop horrendous diarrhea and other complications that can be fatal—same species, different strain compared to the E. coli normally inhabiting your intestine.

So bacterial strain can make a world of difference, the difference between quiet coexistence and death with E coli. The probiotic Lactobacillus casei DN-114001 is effective for reducing diarrhea that occurs after a course of antibiotics, while Lactobacillus casei Shirota does not—same species, different strain. In a large clinical trial to prevent infant sepsis (a life-threatening blood infection), Lactobacillus plantarum ATCC 202195 cut the incidence of sepsis nearly in half, while Lactobacillus plantarum GG did not—same species, different strain. Choosing the right strain can therefore make the difference between a marked beneficial response or no response at all.

Problem: The majority of commercial probiotics fail to designate the strains of the microorganisms contained in their preparations. The Vitamin Shoppe Probiotic Complex Men’s Formula, for example, lists Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus bulgaricus, Bifidobacteria bifidum, and Streptococcus thermophilus—genus and species, but no mention of strains. (These are the species commonly found in yogurt, by the way, especially the Lactobacillus bulgaricus and the Streptococcus thermophilus.) It means that, unless strains are mentioned and compared to the evidence, we won’t really know if a commercial probiotic preparation works to achieve health benefits. We could, of course, trust the manufacturer and their advisers to choose the strains that have solid evidence of efficacy behind them, but it still would be nice to have strains specified on the labels.

In future, I shall be discussing this issue further so that we all have better precision and effectiveness in our choice of probiotics.

(Image courtesy USDA.)