Gold Standard Evidence that Bacterial Overgrowth is at the Heart of IBS

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An overgrowth of bacteria in the gut has been definitively linked to irritable bowel syndrome (IBS), according to the results of a new study at Cedars-Sinai (Los Angeles) which used cultures from the small intestine.

This is the first study to use this “gold standard” method of connecting bacteria to the cause of the disease, which affects an estimated 30 million people in the US alone. Previous studies have indicated that aerobic bacteria play a role in the disease, including breath tests detecting methane – a byproduct of bacterial fermentation in the gut. But this study was the first to make the link using bacterial cultures.

The study, published May 11 by Digestive Diseases and Sciences (“The prevalence of overgrowth by aerobic bacteria in the small intestine by small bowel culture: relationship with irritable bowel syndrome”), examined samples of patients’ small bowel cultures to confirm the presence of small intestinal bacterial overgrowth – or SIBO – in more than 320 subjects. 

In patients with IBS, 37.5% also were diagnosed with small intestine bacterial overgrowth – SIBO [excessive bacteria of the type normally found in the colon, which ferment carbohydrates into gas] – compared to fewer than 10% of those without the disorder.

• Of those with diarrhea-predominant IBS, 60% also had SIBO.

• And of those with constipation predominant IBS, 27.3% had SIBO.

• Overgrowth of Escherichia coli, Enterococcus spp and Klebsiella pneumoniae were the most common isolates found.

• A history of type 2 diabetes and intake of proton pump inhibitors (drugs to reduce stomach acid) were also independently and positively associated with SIBO.

• Gastritis (inflammation of the stomach lining) appeared to be protective against SIBO.

“This clear evidence of the role bacteria play in the disease underscores our clinical trial findings, which show that antibiotics are a successful treatment for IBS,” says Mark Pimentel, MD, director of the Cedars-Sinai GI Motility Program and an author of the study.
Dr. Pimentel first bucked standard medical thought more than a decade ago when he suggested that bacteria played a significant role in the disease. He has led clinical trials showing that rifaximin, a targeted antibiotic that is absorbed only in the gut and not into the circulatory system, is an effective treatment for patients with IBS – and that “Patients who take rifaximin experience relief of their symptoms even after they stop taking the medication.”

“In the past, treatments for IBS have always focused on trying to alleviate the symptoms,” Dr. Pimentel adds, and “this new study confirms what our findings with the antibiotic and our previous studies always led us to believe: Bacteria are key contributors to the cause of IBS.”

The study is a collaboration with researchers at Sismanogleion General Hospital in Athens, Greece, and at the University of Athens.

Sources: Based on the study abstract and Cedars-Sinai Medical Center press release, May 25, 2012

For other reading on bacterial overgrowth in the small intestine, see for example:

“Restless Legs Syndrome is associated with Irritable Bowel Syndrome and Small Intestinal Bacterial Overgrowth,” and “Small Intestinal Bacterial Overgrowth in Patients with Interstitial Cystitis and Gastrointestinal Symptoms,” by Leonard B Weinstock, et al.

“Gut Bacteria, the H2S Test & Mitochondrial Dysfunction in ME/CFS,”  and “Fermentation in the Gut and CFS as a Protective Adaptive Response,” by Sarah Myhill, MD.

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11 thoughts on “Gold Standard Evidence that Bacterial Overgrowth is at the Heart of IBS”

  1. siebertesther says:

    After treatment with Xifaxin for IBS symptoms, my ME/CFS symptoms disappeared! My gastroenterologist didn’t know for sure what was wrong with me and put me on a trial of Xifaxin in October, 2011. I went on a short course of Xifaxin 3 separate times. Each time, my ME/CFS symptoms went away after a few days on this gastro antibiotic and returned in a couple of days after going off of it. I researched the drug, finding that it is used on a maintenance basis for another problem, and requested to be put on it on a maintenance dosage. The treatment dosage is 550 mg. 3X day, then followed by the maintenance dosage of 550 mg. 2X a day. If I find myself relapsing, I go up to the treatment dosage for a time and then return to my maintenance dose. Both my wonderful gastroenterologist and my ME/CFS doctor, Dr. Andreas Kogelnik of Open Medicine Clinic in Mountain View, CA are following my case and supporting me.

    The ironic thing is that gastro symptoms were never front and center in my mind in my 26 years of ME/CFS, often being mild and easily ignored given the difficulty of my other symptoms.

    I’ve just returned from a 19-day trip to 4 cities that would have been impossible to even think about before. And I’m tired but not sick. It has taken me a while to understand what being tired feels like because it is such a mild feeling compared to CFS fatigue. I didn’t remember what being tired felt like from before and had to re-learn to recognize it.

    This recovery has been like a miracle for me and my family and I hope others will be helped by this treatment.

    1. Dusty_V says:

      I was battling IBS for several years. I had to plan my entire life around where the bathrooms were. About 2 years ago I developed a serious case of cellulitus on my left leg. My doctor put me on 2 weeks of Keflex. At the end of the 2 weeks my leg was still bright red but much improvrd. The Doctor put me on another 2 weeks (total 4 weeks. Cellulitus cleared up and as a side benefit the IBS was gone. Been fine for almost 2 years. What a lesson, and guess what, the doctors don’t believe it. Life has returned to life for me and I don’t care if the “professionals” believe it or not.

    2. fixedit says:

      As I understand things, in order to keep problematic bacteria from overgrowing in the small intestine, the stomach must have sufficient hydrochloric acid to do its proper work of breaking down foods and to then trigger the release of bicarbonate in the small intestine. Proton pump inhibitors would inhibit both of these functions and thus, logically, set the taker up for future SIBO, as would a naturally caused insufficiency of stomach acid.

      I have never taken proton pump inhibitors, but have suffered from the results of insufficient stomach acid. When I figured out what was going on, I began taking betaine HCl capsules every few bites throughout each meal. I also began supplementing lactobacillus acidophilus, lactobacillus rhamnosus, and lactobacillus plantarum between meals and before each meal, while carefully avoiding any probiotic supplements containing bifidobacteria and other strains belonging in the large intestine.

      As long as I maintain this regimen, my digestion is normal. But when I fail to do so, the problem returns.

      1. stonehillady says:

        Gluten is now # 1 food allergy & must be tried first for IBS, a very easy inexpensive way to stop it is a teaspoon of aluminum free baking soda- sodium barcarbonate in an 8oz. glass of water before bed time, then in morning a green juiced glass of veggies then a full sprectrum probotic…You have to remember with time anti-bactics will ruin your flora in the gut & can cause all kinds of degestive problems & Candida. If the western medical business cures a disease they would be out of business, that is why they treat only the symptons.
        So, always try the natural ways, they usually have NO side effects as long as you don’t over do it….!

      2. jenunsa says:

        Did I read that correctly? Only 37% of people with IBS have SIBO. If 63% of people with IBS do NOT have SIBO, how is that clear evidence of a role in the disease?
        Seems pretty muddy to me.

        I think SIBO probably doesn’t CAUSE IBS, and vice versa. What is a more logical interpretation of the data is that there is something wrong with certain people which causes them to end up with IBS and/or SIBO. Meaning SIBO and IBS have a common cause, not that one causes the other.

    3. perfectmus says:

      There have been a lot of scientific research and studies just in the last 2 years that prove that colloidal silver, especially the colloidal silver atoms, work very well against these bugs and viruses.

    4. islandsuze says:

      As a Registered Nurse I “probably” over think things esp when it comes to my own health. A little less than 5 years ago I had what seemed like overnight bloating and distention that made me appear to be pregnantshortly after returning from a volunteer experience in Honduras. Being of normal weight this was quite startling. I had always been “healthy” and had little need to visit a doctor except for minor infections on very rare occasions. After visiting my doctor and having an ultrasound/CT scan/MRI/colonoscopy/parasite testing the only findings were some ovarian cysts/uterine fibroids and a diagnosis of IBS-C. Honestly I do not like the diagnosis of IBS as it seems like a catch all diagnosis when they do not know what is “really” wrong. Being frustrated with this diagnosis I continued to research trying to diagnose myself in hopes of finding some relief. I started feeling like a hypochondriac and what started out “a large and uncomfortable abdomen” seemed to tumble into other diagnoses such as hypothyroid, diabetes, spondylosis, depression, low vitamin D. The odd thing was I gained a large amount of weight, water/fat not really sure but I am no longer recognizable in my passport photo-always asked for additional identification to prove who I am–even asked “what happened to you” that is depressing in itself. Leading to feeling frustrated and at the point of just giving up. Recently I was diagnosed with a UTI that cultured for klebsiella pneumoniae–now 4 antibiotics later and this bacteria doesnt seem to be bothered. Actually finding this bacteria has given me some type of hope. Perhaps I could have an overgrowth of this bacteria and just maybe this could be the cause of this decline of my health. I really hope so–I would really love to have my old life back. Now if I can find a doctor who will listen. I would love to know what would be found in a complete stool analysis, and the breath test for overgrowth. I have enjoyed reading the info I have come across giving me the hope to continue the fight for my health.

    5. Bluetou says:

      Just wondering if you are feeling better – you mentioned you have klebsiella pneumoniae – I also have this and was diagnosed via stool test form doctors data – would love if you could check in and share protocol Thnk you

    6. Funyuns says:

      You can use grapefruit seed extract. Start with 5 drops and work up to 15-20 drops 3x a day. Go slow as it is powerful. You can also eat 1 clove of garlic per day after you have gotten your GSE up a bit. I had this come back on a stool test as well. I am working with Eric Bakker to resolve this and a few other things that showed up. You can also purchase CanXida Remove which has all of these items plus more. I started with the GSE before working with Eric and I was winging it. I was also doing the silver. I may go back to the GSE and silver as it seems as though it was working well and I could pave myself easier. I was told it would take about 3 months to turn this around.

    7. SeaVitality says:

      Many thanks for all the detail from the nurse who returned from Honduras, basically, as no longer her former (inner) self. So, before she traveled…and relative to likely mandated vaccines and possibly otherwise drugs, were there any in the ‘broad spectrum’ fluorquinolone class, specifically as ‘Cipro’?

      Everything mentioned sounds so similar to what has evolved for my daughter after she was prescribed Cipro for UTI…and while not knowing to avoid alcohol, suffered a very BAD (acute neurological/physical) reaction on the 5th day (500 mg/2xday) which, since we were together, I first learned about and told her to stop using due to slew of negative reactions I’d already seen happen with others after exposure to this ‘former chemotherapy/fluorine based’ (in my book) poison.

      Thus, after such brain (and liver) trauma, there were many weeks before she felt like herself, but over the course of time, so has she developed the ‘p.g.’ (sized) bloating and other symptoms of what I believe are akin to SIBO. Unfortunately, my investigation does confirm that, even though she used this antibiotic more than a year ago, Cipro (likely all fluoroquinolones) CAN incite this problem (dysbiosis, imbalances of overgrowth) in the lower intestine. And since the nurse mentions, so has she been hit with new issues of elevated DHEA (not PCOS) and deficiency of thyroid function…which, altogether, have added weight…even though she’s knowledgeable about dietary choices and has been a years-dedicated (including Marathons) fitness buff.

      Anyway, the reason I’m here was because I’ve just today learned how the lactic acid probiotic L. Plantarum can be meaningfully helpful for IBS and SIBO…which, even intuitively, sound ‘cousin’ related to me…so, after finding the Clinical Trial (elsewhere) first, it’s been doubly great to see ProHealth’s confirmation with the ‘gold standard’ post and to view detail of the nurse’s ‘echo-ing’ experience. Needless to say, I hope we both soon navigate a positive route to the absolute bottom (revealed truth) of these very unpleasant situations.

  2. Minnesota says:

    At the time of the study, 60% of those in the study group with diarrhea-predominant IBS had active SIBO that could be cultured. Then 27.3% of the constipation-predominant group had active SIBO at the time of the study, bringing down the incidence for the overall study group. I tend to agree, it may be that SIBO is a result rather than cause for these individuals, but it seems that determining the type of active SIBO if any that a person with IBS is harboring would allow for resolution of the overgrowth via targeted antibiotics and/or probiotics.

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