Dysbiosis (also called dysbacteriosis) is a microbial imbalance or maladaptation on or inside the body,[1][2] such as an impaired microbiota. For example, a part of the human microbiota, such as the skin flora, gut flora, or vaginal flora, can become deranged, with normally dominating species underrepresented and normally outcompeted or contained species increasing to fill the void. Dysbiosis is most commonly reported as a condition in the gastrointestinal tract,[2] particularly during small intestinal bacterial overgrowth (SIBO) or small intestinal fungal overgrowth (SIFO).[3][4]

Typical microbial colonies found on or in the body are normally benign or beneficial. These beneficial and appropriately sized microbial colonies carry out a series of helpful and necessary functions, such as aiding in digestion.[5] They also help protect the body from the penetration of pathogenic microbes. These beneficial microbial colonies compete with each other for space and resources.[6]


Dysbiosis may be caused by such diverse things as antibiotic or mold exposure,[7][8][unreliable medical source?] alcohol misuse,[9][10] or inappropriate diet.[11][unreliable medical source?]


When this balance is disturbed, these colonies exhibit a decreased ability to check each other's growth, which can then lead to overgrowth of one or more of the disturbed colonies which may further damage some of the other smaller beneficial ones in a vicious cycle. As more beneficial colonies are damaged, making the imbalance more pronounced, more overgrowth issues occur because the damaged colonies are less able to check the growth of the overgrowing ones. If this goes unchecked long enough, a pervasive and chronic imbalance between colonies will set in, which ultimately minimizes the beneficial nature of these colonies as a whole.

Microbial colonies also excrete many different types of waste byproducts.[12] Using different waste removal mechanisms, under normal circumstances the body effectively manages these byproducts with little or no trouble. Unfortunately, oversized and inappropriately large colonies, due to their increased numbers, excrete increased amounts of these byproducts. As the amount of microbial byproducts increases, the higher waste byproducts levels can overburden the body's waste removal mechanisms.

It is the combination of these two negative outcomes that causes many of the negative health symptoms observed when dysbiosis is present.

Associated illnessesEdit

Disruptions in the microbiome can allow outside factors or even pathogenic members of the microbiome to take hold in the gut environment. Dysbiosis has been reported to be associated with illnesses, such as multiple chemical sensitivity, periodontal disease,[13] inflammatory bowel disease,[14][15] chronic fatigue syndrome,[16] obesity,[17][18] cancer,[19][20] bacterial vaginosis,[21] and colitis.[22]


Sustained periods of dysbiosis lead to extended amounts of stress and inflammation in the gut microbiome, which can in turn promote the production of carcinogenic metabolites.[23]

Clostridioides difficileEdit

C. difficile is an opportunistic bacteria that commonly infects patients following a disruption in the microbiome, such as treatment with antibiotics.[24][25] Infection can lead to several different symptoms including watery diarrhea, fever, loss of appetite, nausea, and abdominal pain.[26] Severe or chronic infections of C. difficile can lead to inflammation of the colon, a condition known as colitis.[27]


Periodontitis is an oral infection that can damage the bones supporting teeth and lead to tooth loss.[28] One of the major risk factors for periodontitis is the disruption of the oral microbiome such that there is an accumulation of pathogenic bacteria.[13]



Because of the complex interactions in the microbiome, not much data exists on the efficacy of using antibiotics to treat dysbiosis. However, a broad-spectrum antibiotic that has low impact on the intestinal gut microbiome called rifaximin, has been shown to be effective in improving several of the ailments associated with dysbiosis, including irritable bowel syndrome,[29] ulcerative colitis[30] and Crohn's disease.[31]

Fecal microbiota transplant (FMT)Edit

FMTs use the same line of reasoning as probiotics; to recreate a healthy balance of microbiota in the microbiome by inserting beneficial microbes into the environment. FMT accomplishes this by taking a donation of fecal matter from a healthy individual, diluted, strained and introduced to a diseased patient.[32] FMTs are currently used to treat patients with Clostridium difficile infections, who have proved resistant to other therapies.;[33] however, this is considered an investigational therapy at present with risks that have not been fully defined.[34] Because the process is not sterile and contaminations can pass from donor to patient, there is a push to isolate key microbiota and culture them independently.[35]


The World Health Organization defines probiotics as "live microorganisms, which when administered in adequate amounts, confer a health benefit on the host".[36] The benefit of using probiotics to treat dysbiosis related diseases lies in its ability to treat the underlying cause of said diseases. Some benefits include their ability to suppress inflammation in the microbiome[37][38] and disrupt colonization by pathogens.[39]

See alsoEdit

Notes and referencesEdit

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  2. ^ a b Moos WH, Faller DV, Harpp DN, Kanara I, Pernokas J, Powers WR, Steliou K (2016). "Microbiota and Neurological Disorders: A Gut Feeling". BioResearch Open Access. 5 (1): 137–145. doi:10.1089/biores.2016.0010. PMC 4892191. PMID 27274912. As reviewed in this report, synthetic biology shows potential in developing microorganisms for correcting pathogenic dysbiosis (gut microbiota-host maladaptation), although this has yet to be proven.
  3. ^ Fujimori S (June 2015). "What are the effects of proton pump inhibitors on the small intestine?". World Journal of Gastroenterology. 21 (22): 6817–6819. doi:10.3748/wjg.v21.i22.6817. PMC 4462721. PMID 26078557. Several meta-analyses and systematic reviews have reported that patients treated with PPIs, as well as post-gastrectomy patients, have a higher frequency of small intestinal bacterial overgrowth (SIBO) compared to patients who lack the aforementioned conditions. Furthermore, there is insufficient evidence that these conditions induce Clostridium difficile infection. At this time, PPI-induced dysbiosis is considered a type of SIBO.
  4. ^ Erdogan A, Rao SS (April 2015). "Small intestinal fungal overgrowth". Current Gastroenterology Reports. 17 (4): 16. doi:10.1007/s11894-015-0436-2. PMID 25786900. Small intestinal fungal overgrowth (SIFO) is characterized by the presence of excessive number of fungal organisms in the small intestine associated with gastrointestinal (GI) symptoms. Candidiasis is known to cause GI symptoms particularly in immunocompromised patients or those receiving steroids or antibiotics. However, only recently, there is emerging literature that an overgrowth of fungus in the small intestine of non-immunocompromised subjects may cause unexplained GI symptoms. Two recent studies showed that 26 % (24/94) and 25.3 % (38/150) of a series of patients with unexplained GI symptoms had SIFO. The most common symptoms observed in these patients were belching, bloating, indigestion, nausea, diarrhea, and gas. The underlying mechanism(s) that predisposes to SIFO is unclear but small intestinal dysmotility and use of proton pump inhibitors has been implicated. However, further studies are needed; both to confirm these observations and to examine the clinical relevance of fungal overgrowth, both in healthy subjects and in patients with otherwise unexplained GI symptoms.
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