How to read a probiotic strain name, step by step

Lactiplantibacillus plantarum 299v looks less like an ingredient and more like a Wi-Fi password. But every piece of that name tells you something, and the short code at the end is the piece that matters most.

Probiotic labels are full of names like this, and most people skim right past them. Here's how to decode one in four steps, and why the strain code deserves a few seconds of your attention before you buy.

Step 1: Find the genus (the first word)

The first word is the genus, a broad group of related microbes. On probiotic labels you'll most often see Lactobacillus, Bifidobacterium or Saccharomyces, which is a yeast.

If some genus names look unfamiliar, there's a reason. In 2020, microbiologists used whole-genome data to reorganize the old genus Lactobacillus, which then held 261 species, into 25 genera (Zheng et al., 2020). Several well-known species got new first names:

• Lactobacillus plantarum became Lactiplantibacillus plantarum
• Lactobacillus rhamnosus became Lacticaseibacillus rhamnosus
• Lactobacillus reuteri became Limosilactobacillus reuteri
• Lactobacillus acidophilus stayed in the genus Lactobacillus

So a newer label that says "Lactiplantibacillus" and an older study that says "Lactobacillus" can be describing the same bacteria. The species name and the strain code stay the same, so those are what you should match.

Step 2: Read the species (the second word)

The second word is the species, such as plantarum, rhamnosus or acidophilus. Sometimes a subspecies follows, marked "subsp."

Genus plus species tells you what kind of microbe you're looking at. It doesn't tell you what that particular product will do, because members of one species can behave very differently. That's where the next step comes in.

Step 3: Look for the strain code

The strain designation is the letters, numbers or both after the species: 299v, GG, HN019, NCFM or CNCM I-745, for example. Think of the species as a last name and the strain as a first name. Plenty of people share a last name and have little else in common.

You may also see a culture collection number, which is the ID a strain gets when it's deposited in an official collection. Lactiplantibacillus plantarum 299v, for example, is also listed as DSM 9843 in research (Ducrotté et al., 2012).

If a label lists only "Lactobacillus acidophilus" or "Bifidobacterium blend" with no code, you have no way to look up what that exact strain has been tested for.

Step 4: Check what that exact strain was studied for

This is where strain names stop being trivia. Two strains of the same species can have opposite results in people. Here's a clear example with Lactiplantibacillus plantarum:

• Strain 299v. In a double-blind trial with 214 adults with IBS, one capsule a day for 4 weeks lowered the severity and daily frequency of abdominal pain compared with placebo, with similar results for bloating. At week 4, 78.1% of people taking 299v rated its effect as excellent or good, compared with 8.1% on placebo (Ducrotté et al., 2012).
• Strain MF1298. Researchers picked this strain because it had the best lab-tested probiotic properties out of 22 lactobacilli they screened. In a small crossover trial with 16 people with IBS, 13 of them preferred the placebo period, and symptom scores were worse while they took the strain (Ligaarden et al., 2010).

Same species, opposite results. Strong performance in a lab dish didn't predict how people actually felt.

A review of 228 trials put this more formally: probiotic effects are both strain-specific and disease-specific. For antibiotic-associated diarrhea in adults, for instance, certain Lactobacillus strains showed a benefit while other Lactobacillus strains didn't, and some well-known strains worked for one condition but not another (McFarland et al., 2018). The authors warn that reviews lumping different probiotics together can lead to misleading conclusions.

Putting it together: a label example

Say a label reads "Lactiplantibacillus plantarum 299v, 10 billion CFU." Here's how to read it:

1. Genus: Lactiplantibacillus, formerly part of Lactobacillus.
2. Species: plantarum.
3. Strain: 299v, the part you can search for.
4. Amount: 10 billion colony-forming units. Check whether that amount is guaranteed through the expiration date or only at the time of manufacture.

Then compare the strain and amount with the studies you're relying on. A trial of one strain supports that strain at a similar dose, for the symptom that was measured. It doesn't support the whole species.

Quick tips for the store or the screen

• A strain code is a good sign of transparency, but it isn't proof of a benefit on its own.
• A long list of species without strain codes makes it hard to check anything.
• Older studies use the old genus names, so search both the new and old versions.
• Make sure the symptom you care about is the one the strain was actually studied for (McFarland et al., 2018).

If you find a well-studied strain that fits your goal, give it a consistent, well-tracked trial. Here's what a realistic timeline looks like.

Sources

1. Zheng J, Wittouck S, Salvetti E, et al. A taxonomic note on the genus Lactobacillus: description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae. Int J Syst Evol Microbiol. 2020;70(4):2782-2858. PMID 32293557
2. Ducrotté P, Sawant P, Jayanthi V. Clinical trial: Lactobacillus plantarum 299v (DSM 9843) improves symptoms of irritable bowel syndrome. World J Gastroenterol. 2012;18(30):4012-8. PMID 22912552
3. Ligaarden SC, Axelsson L, Naterstad K, Lydersen S, Farup PG. A candidate probiotic with unfavourable effects in subjects with irritable bowel syndrome: a randomised controlled trial. BMC Gastroenterol. 2010;10:16. PMID 20144246
4. McFarland LV, Evans CT, Goldstein EJC. Strain-specificity and disease-specificity of probiotic efficacy: a systematic review and meta-analysis. Front Med (Lausanne). 2018;5:124. PMID 29868585

This article is for general information and isn't medical advice. Talk to your healthcare provider before starting a probiotic, especially if you're pregnant, nursing, immunocompromised or take prescription medication.