Specific live cultures strains

At OptiBac we specialise entirely in live cultures, and in particular we use different strains for different groups of people and for different reasons. We aim to offer each of our customers a specific supplement to suit their individual needs. When it comes to live cultures, it is not a question of 'one-size-fits-all'!

What is a live cultures strain?

Many people (healthcare professionals included) misunderstand the definition of a 'strain'. Read on to make sure you are in the know.

The term ‘strain’ refers to a biological variety within a species; a species in turn, exists within a genus. For example, the name Lactobacillus acidophilus Rosell-52 tells you the name of the genus (Lactobacillus), the species (acidophilus), and the strain (Rosell-52). Different manufacturers use different strains, although these may be of the same species and genera; meaning that one acidophilus supplement is not equal to another acidophilus supplement. It is hence best to choose a live culture supplement that uses robust, well-researched strains.

Image show how, for the live cultures strain named 'Lactobacillus acidophilus Rosell-52': 'Lactobacillus' is the genus, 'acidophilus' is the species, and 'Rosell-52' is the strain.
Live cultures strain naming convention explained

Many of our strain names include 'Rosell' as they originated from, and have been rigorously tested by, the leading firm in the field, Institut Rosell.

For further clarification on the difference between a genus, a species and a strain, please see the relevant terms in our glossary, or read 'The Strain Myth', both of which are in the Probiotics Learning Lab.

Viable, effective strains

As well as selecting the optimum live cultures, it is important to consider the viability and efficacy of the strains themselves. The strains must be alive at the time of consumption, and must survive the stomach acidity in order to reach the intestines. The OptiBac live cultures strains undergo numerous in-vitro (see Probiotics Learning Lab) tests documenting their viability at room temperature, and to survive the acidic stomach environment and bile salts.

Featured OptiBac strains

Lactobacillus acidophilus NCFM® is the most well-researched L. acidophilus strain in the world, with over 45 clinical trials. NCFM stands for the 'North Carolina Food Microbiology' research laboratory, where it was first identified in the 1970s. Find Lactobacillus acidophilus NCFM® in 'For every day EXTRA Strength'.

Bfidobacterium lactis BB-12® is likely the world's most well-researched strain of the entire Bifidobacteria genus. It has been trialled and shown to be safe for a number of different populations, including pregnant women, children and the elderly. Find Bifidobacterium lactis BB-12® in 'Bifidobacteria & fibre'.

B. lactis BB-12 as seen under microscopic inspection

Lactobacillus reuteri RC-14® & Lactobacillus rhamnosus GR-1® is a very unique combination of strains, that has been clinically proven to reach the intimate area alive. This combination of strains (the two have mostly been trialled as a pair) has over 30 years of clinical research, in more than 26 clinical trials including over 2,500 women. Find Lactobacillus reuteri RC-14® and Lactobacillus rhamnosus GR-1® in 'For women'.

Bifidobacterium infantis Rosell-33 has been scientifically demonstrated to reach the guts of children alive. Unlike L. acidophilus, B. infantis mainly resides in the large intestine or colon of children. Find Bifidobacterium infantis Rosell-33 in 'For babies & children'.

Microscopic image of two B. infantis Rosell-33 cells

Saccharomyces boulardii is an internationally acclaimed yeast that works in a very different manner to our other strains. Saccharomyces boulardii is actually transient, and has undergone rigorous clinical research to demonstrate, amongst other things, its ability to reach the gut alive. Find 'Saccharomyces boulardii' in our shop.

Under the microscope: S. boulardii cells are naturally much larger than other microbes

Lactobacillus rhamnosus Rosell-11 & Lactobacillus acidophilus Rosell-52 is an incredibly well researched combination of strains.This combination of friendly bacteria has over 31 clinical trials in support of them, and have been scientifically proven to reach the gut alive, even during a course of antibiotics. Find Lactobacillus rhamnosus Rosell-11 and Lactobacillus acidophilus Rosell-52 in 'For every day'.


In conclusion, it is very important to look at friendly bacteria on a strain-specific level, rather than only the genus and species of microorganism in question. To find out more about the OptiBac range, take a look at the shop, or our recent blog post, 'Want the Best Live Cultures? 5 Reasons we're the Best.'

Friendly bacteria strains in OptiBac supplements
OptiBac live culture strains - which one's right for you?


  • What's the best probiotic regime for SIBO?

    What dosages?


  • Response from OptiBac Probiotics

    Dear Deep,
    One of our naturopaths will e-mail you regarding your question.

    Kind Regards,

  • A perfect detailed yet succinct reference for me to use when advising customers in the shop I work in! Thank you :)

  • Hi, can you tell me what the "NCFM" as the strain stands for? Also, I've heard that the best strain is DDS-1. I'd love your opinion on that please. Also, to what percentage in tests are your strains acid and bile resistant, ie. >90% for example? Many thanks.

  • Response from OptiBac Probiotics

    Dear Sam

    Thanks for your comment.

    Unfortunately I am not in a position to comment on other strains as I do not have access to their studies. I can however inform you that NCFM stands for North Carolina Food Microbiology as the strain was first isolated and registered at North Carolina University in the USA, and it is probably one of the most clinically trialled strains of probiotic bacteria in the world.

    At OptiBac Probiotics we focus on the research behind the strains, and Lactobacillus acidophilus NCFM has been clinically trialled in a huge amount of studies.

    Regarding resistance to bile and acidity, the strains in the OptiBac Probiotics range were developed to survive gastric acidity above (i.e. more neutral than) pH 3. In-vitro trials on our probiotic strains show a 95 - 100% survival rate through gastric acidity at this pH. Research from microbiologists shows that at mealtimes (and especially breakfast time) the stomach's gastric acidity is naturally at pH 4 or above. If you would like to read more about this please see here: https://www.optibacprobiotics.co.uk/resource-centre/faq/category-general-faqs/13-at-what-time-should-i-take-probiotics.html

    Kind regards,

    In-house nutritional therapist

  • Hi,

    I have IgA Immune disorder and was wondering what specific strain of probiotics should I be taking.


  • @ AL
    Thank you for your interesting question regarding the use of live cultures by sufferers of IgA immune disorders.
    I am going to request that my colleague Megan emails you directly about this complex issue.

  • what would be the best probiotic strains to take after an operation for an infection around the brain and while still on heavy antibiotics? Is this advisable?


  • Dear Maureen,

    Thank you for your question. Generally speaking probiotics are one of the safest food supplements available on the market, but for a very small percentage of our customers, notably those who have had major surgery with open wounds, or who are very ill in hospital, probiotics are not advised or are to be used only with the agreement of your doctor.

    For more safety information, please see our page ‘When should I NOT take probiotics?

    Many of the situations listed in this safety information are very prudent and anticipating the worst case scenario. Many people who have the health conditions listed in the safety section have in fact taken probiotics with no negative effects, but there have been very rare incidences where the person has experienced a negative effect and we cannot be sure if the probiotics were the cause of the deterioration or not. This is why we must always err on the side of caution to minimise all potential risks to the individual.

    Many probiotic companies don’t even make the consumer aware of cautions! This goes to show how very infrequently they arise. We just like to be ultra careful and transparent, so that if there happens to be any reason for hesitation then you and your doctor can make an informed decision.

    I hope that this answers your question, but if you require any further information, please do not hesitate to contact me on [email protected]

    Wishing you the best of health,


  • Al
    I think I have finally convinced a friend to start on a strain but we are so lost & don't know were to start. She has had in the pass c diff but for now the major problems are IBS-D, Addisons Disease & Ulcerative Colitis. She has bloating & cramping so we need to stay away from any strains that induce bloating & cramping if possible.
    Many thanks, Dave

  • Truly, not all probiotics are helpful for all kinds of illnesses. Primarily, probiotics function to help flourish our gut with the good bacteria that it needs. However, there are specific bacteria strains needed for specific ailments.

  • What strain would be best for excess acid. I am on 40mg of om****zole and would like to get off it.

  • @ Jeff,

    Probiotics are primarily active in the intestines rather than the stomach; however, sometimes stomach issues can be aggravated by intestinal dysbiosis.

    If this is the case, then taking a good broad-strain probiotic may be most suitable.

    Wishing you the best of health,


  • I have severe psoriasis and was wondering which of your products would help me most?

  • Hi Lorraine,

    Thanks for your question.
    It's interesting that you're looking for a probiotic to help support skin conditions such as psoriasis and eczema.

    Unfortunately, we don't currently offer a product specifically for this purpose.

    Do feel free to contact me directly on [email protected] should you wish to discuss your individual probiotic needs in more detail.

    Warm wishes,


  • Hi,
    Do you have information on the BB06 strain?

  • Response from OptiBac Probiotics

    Dear Cza,

    Thank you for your query.
    Unfortunately, Bifidobacterium bifidum Bb-06 is not a strain that we carry within our range, and I am not in a position to comment on other strains as I do not have access to their studies.

    Kind regards,

    Nutritional Advisor
    OptiBac Probiotics

  • I get plenty of probiotics from the usual food sources, i.e. yoghurt, probiotics from the health food store (those sweet "yogurt-like" probiotics that come in little plastic wide-mouthed bottles). I would like to take probiotics that are naturally found in human body. What probiotics do you sell that are only found in the human body? Thank you!

  • Response from OptiBac Probiotics

    Hi Ecira,

    Thanks for your question.

    Firstly, whilst its great to include a wide variety of fermented foods in the diet, you need to be careful that those you choose don't contain lots of sugar or sweeteners, and also you need to consider that often the strains of bacteria in these type of foods are 'transient' in nature, meaning that they're not going to colonise in the digestive tract for any length of time.

    There are a lot of misconceptions and myths circulating about this subject, and how we can obtain the right strains of probiotics for our needs, and whether its possible to do this by diet alone.

    Our 'For every day EXTRA Strength' product contains almost all 'human strains' of bacteria. The key consideration you should have is whether you are choosing the correct strain of bacteria to best suit you.

    Our website offers a wealth of information about our products to help you make an informed decision, but you're also welcome to contact us directly using our Contact Form if you'd like more advice about which probiotic is best for you.

    Kind regards,

    Nutritional Advisor
    OptiBac Probiotics

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