Proteus predominant IBS

IBS patients whose MS-microbiology tests reveal massive colonization by Proteus spc
The only case against glutamine supplements for IBS

Proteus spc in green environment
Number of cases
Mean age
Rate of success
3-6 months
Treatment duration
Most common symptom
Chronic glutamine intake
Most common culprit
Improvement score
Loose stool
Residual feeling
Stomach upset

Proteus and Proteus-like bacteria are potent non-commensal bacteria. They possess many enzymatic activities and produce several symptoms within the spectrum of IBS. Most commonly recovered species are P. mirabilis and P. vulgaris. Other similar bacteria are Morganella morganii and Providencia rettgeri. Besides their incredible histamine–producing capacity, these microbes have the ability to translocate and perform an action called “swarming”. Swarming takes place in response to several stimuli. One of the most studied is contact with glutamine. This is why glutamine should never be prescribed in IBS-D patients before Proteus colonization is excluded. 

Proteus-derived harmful products



Biogenic amine that also causes extra-intestinal symptoms


In large amounts becomes toxic to mucosal surfaces


Alkalizes the acidic intestinal environment and permits pathogenic bacterial growth


Flatulence, bloating

Jason’s symptoms started about a year before he came to my office. He was on vacation with his family in a rural region in Greece and he remembers that the night he first noticed bloating and itching was after a seafood meal. He thought it was something transient and did not take any action; but as the symptoms worsened day by day, he decided to visit a doctor. To cut a long story short after 3 terrible months he had visited 3 gastroenterologists and a general practitioner. All of them gave the same diagnosis. Stress-induced IBS and the advice was “…you need to relax”.

Trigger - Effect timeline
Lifestyle habits
Gradual mucosal deterioration

Poor lifestyle habits adversely condition the intestinal microenvironemnt favoring the colonization and overgrowth of pathogenic bacteria
Potent antibiotics
Microbial diversity reduction

An already compromized intestinal microenvironment is very sensitive to the destructive effects of antibiotics, especially when taken multiple times in a short period of time
Seafood consumption
Probable Proteus inoculation

Proteus spc as well as other pathogenic bacteria are commonly found in seafood and when ingested may inhabit rapidly a compromized gut
Fiber avoidance
Diminishing of commensal bacterial populations

Due to his symptoms, he avoided vegetable and fruit consumption leading to the shrinking and worsening of microbiome diversity
not every ibs is the same. find yours!
over 1400 real cases.

From the beginning, my suspicion was a microbiologically induced histamine overload. So a complete stool test was the first thing to order. This test, besides a thorough look at Jason’s microbiota included eosinophil derived proteins in his gut, mucosal immunity biomarkers and excretion of fats, proteins and starch. In addition, among others, I wanted to see the activity of the histamine-degrading enzyme DAO along with the histamine burden in Jason’s serum. 


Histamine, a product of Proteus metabolism, increases colonic contractions, leading to the feeling of urgency​

Both the abuse of whey protein and the histamine content of his gut modulate the regulation of gastric acidity and function​

The aforementioned water and mucus excretion make stool consistensy loose and, sometimes, watery​

The constant metabolic actions of this bacterium makes the colon excrete water and mucus giving rise to the defecation sensation with less colonic content​

Seafood consumption as the trigger
High sulfur foods exaggerate symptoms
Rectal itching
Glutamine abuse
Low grade ileal inflammation

The results showed an excess of histamine in his gut and an elevated sIgA titer which mean that a bacterium capable of releasing vast amounts of histamine should be the culprit. Indeed, his microbiology profile showed markedly elevated levels of Proteus vulgaris. In fact the levels were off the upper limit of the method’s sensitivity which means that in a given microregion of the microscope there were over 25 cells of Pvulgaris instead of 0!!! Almost 10 indices of gut absorption and ifnlammation were way above normal limits.

Actionable exam results (4 out of 10)

Proteus vulgaris

A gram negative bacterium with potent histamine producing capacity which preferentially colonizes the terminal ileum giving rise to subclinical inflammation

Stool histamine

Massive amounts of histamine activate HCl excretion in the stomach producing the symptom of discomfort. In addition, histamine may diffuse in the bloodstream and produce itching

Fecal fat

Elevated levels of fecal fat produce steatorrhea, a condition responsible for loose stool and sometimes urgency

Elevated sIgA

Elevated sIgA was probably due to Proteus colonization. As a results there is immune weakening and mucosal surface thickening​


The rational of his treatment is based on the vastly disordered mucosal surfaces. It is these surfaces and the altered gut environment that favored Proteus colonization in the first place, which in turn inflamed the ileum and started producing histamine. Consequently, bloating, lipid malabsorption and several extra-intestinal symptoms appeared. This kind of treatment almost always produces augmented symptoms for several days, since while Proteus cells start dying, they release a lot more histamine and LPS, which will inevitably get into the bloodstream. 

Follow up

The first thing he told me was that his migraines and itching were a thing of the past. With regards to his bowel symptoms, he was still feeling bloated but not all day and the severity was milder than before. Up to day 24 of the program his stools remained loose but in the last 4 days he had noticed more formed and complete defecations.

His rating of improvement was 90% but my score was only 70%. Sometimes, when patients get a little better they rate their health very optimistically. I told him to continue his treatment in exactly the same way and to come back and see me in two months. He returned to my office with his wife, who confirmed his improvement.


Proteus is a rather difficult bug to eradicate and this is why treatment in this context is usually longer. The patients are usually less tolerant and that’s why the doctor-patient communication needs to be very careful. It must be explained to the sufferer that what they are about to do is not a treatment but a plan that may last up to 6 months. Proteus cases are usually chronic, meaning that the damage that the gut ecosystem has suffered, because of its presence is larger. Generally, these microbes cannot colonize our ileum unless the physiological variants like pH, mucosal depth and probiotic sterility allow it. Once these bacteria colonize the gut, they start producing substances that favor their development and produce annoying symptoms to the host.

Every part of this case study is fully analyzed in the book IBSyncrasy and includes complete case description, diagnostic procedure, treatment and follow-up
Theodoros Prevedoros
With extensive experience evaluating over 3000 cases in various specialties, including gastroenterology, pediatrics, and endocrinology, Theodoros has collaborated with more than 25 doctors from Greece and Cyprus and over 10 laboratories worldwide.

With a background in Chemistry and Biochemistry from the National and Kapodistrian University of Athens, Theodoros brings a wealth of knowledge in functional medicine and advanced treatments to his role. He possesses exceptional skills in analysis, pattern recognition, diagnostic translation, and storytelling. He is also FMU certified in Functional Medicine and has received training in advanced treatments from the Saisei Mirai Clinic in Japan.