Yeast, Clostridia and Viruses

… Oh and good bacteria too!


A healthy digestive tract contains both yeast and good bacteria.  The balance of good bacteria to other microbes plays an  important role in regulating inflammation, digestion and immune function.   

What is dysbiosis?

Dysbiosis is an imbalance in the natural flora of the digestive tract.  Bacteria in the gut has the potential to overgrow which creates inflammation, decreases nutrient absorption and, in the case of autism, impairs development.  The natural balance of good flora or probiotics in the digestive tract is essential to regulate immune function.  A lack of good bacteria or an overgrowth of unhealthy microbes can cause major problems for children with developmental disorders.


Bacteria live in the intestinal tract, sharing space with yeast. Antibiotic use makes creates the opportunity for yeast overgrowth.  Antibiotics kill both good and bad bacteria, but not yeast.  Children who have been on antibiotics many times without re-populating the digestive tract with good bacteria, will undoubtedly have issues with yeast overgrowth.  Many children are born with dysbiosis or imbalance in the gut flora because of C-section birth, IV antibiotics during birth and/or formula feeding, all of which contribute to yeast overgrowth.

Yeast live and feed on sugar.  Limiting high sugar (or foods that turn into sugar in the gut) is the first and most important step.

Signs of Yeast Issues


  • Demanding
  • Non-compliant
  • Aggressive
  • Stimming
  • Hands over ears
  • Chewing (on everything and anything) and teeth grinding
  • Laughing for no reason, in the middle of the night or spontaneously during the day
  • Climbing all the time
  • Standing on head or hanging upside down all the time
  • Brain fog: giddy super-silly behaviours
  • Loss of energy
  • Seeming out of it
  • Craving for bread, pasta and sweets

Clinical Signs:

  • Rashes
  • Eczema
  • Funky-smelling scalp (the “wet dog” smell)
  • Itching: perianal, genital and/or generalized
  • Redness: around the anus or vagina
  • Abdominal bloating
  • Increase in flatulence
  • Constipation or diarrhea
  • Change in smell of stool (yeasty, bready, foul or sweet)



Research by Dr. Sidney Finegold compared the gut flora of children with regressive ASD to neurotypical children.  The results show that clostridial counts were higher in the children with autism. The number of clostridial species found in the stools of children with ASD was greater than in the stools of neurotypical children. Children with ASD had 9 species of Clostridium not found in the neurotypical group.  The neurotypical group showed only 3 species not found in children with autism. In all, there were 25 different clostridial species found. In stomach and small intestine specimens, the most striking finding was total absence of Clostridia from neurotypical children and significant numbers of such bacteria from children with autism.

These studies demonstrate significant alterations in the upper and lower intestinal flora of children with late-onset ASD and may provide insights into the nature of this disorder.

Research by Dr. Derrick McFabe, at the University of Western Ontario, has explored aquired Clostridia infection and it’s relation to autism spectrum disorder.  In his study, rodents injected with propionic acid (from Clostridial species) displayed autism like behaviours including:

  • Spinning
  • Repetitive behaviours
  • Seizures / convulsions
  • Pushing away
  • Hyperactivity
  • Altered social interaction and impairment in “play” like behaviour

Here are some ways that Clostridia could play a role in autism

  • Too much Clostridia
  • Impaired immune activity
  • Damage to digestive tract
  • Nutrient deficiencies
  • Inflammation
  • Diet

A video about Dr. MacFabe’s research can be seen at Autism Canada Foundation 



There is significant evidence that implicates the immune system in autism, PDD, ADHD and other developmental issues.  Pre and post natal infection are known risk factors for ASD and many parents report the onset of autism symptoms after viral infection.

Viruses induce a response from the immune system.  The immune system response creates inflammation.  Research by Dr. Pardo, Dr Vargas and Dr. Herbert have shown definitively that inflammation plays a key role in ASD.  Dr. Pardo and Dr. Vargas examined children and adults with autism who had passed away.  Their findings showed an ongoing inflammatory process in the brain.  This is important evidence in showing that autism is neurobiological in nature – that something impacting the body and brain is causing autism.

 Viruses can trigger a misguided immune response that can cause disruptions that can impact:

  • development
  • behaviour
  • mood
  • skin
  • digestion
  • immune function
  • sleep

Researchers found that autistic children who had been exposed to certain viruses in the past showed high levels of antibodies to brain proteins, suggesting an autoimmune response. Their findings appear in the October issue of the peer-reviewed journal, Clinical Immunology and Immunopathology.

It is well known that genetic interaction with the environment is the cause of autism.  Which genes and which environmental triggers is more difficult to understand.  Likely, subgroups of autism will be found to be associated with different genes and different environmental triggers.

Early exposure to a virus can cause the body to mount an immune response.  This is a response that has the potential to go awry. In addition to producing antibodies against the virus, the body makes antibodies against itself, resulting in damage to tissues and organs.

This “autoimmune” response is what happens in autoimmune diseases such as lupus, and some researchers think a similar response may account for the brain abnormalities found in people with autism, PDD, ADHD.

A study of 48 autistic children and 34 normal children and adults, the researchers measured levels of antibodies to two viruses—measles virus and human herpesvirus-6—in the subjects’ blood. These antibodies were chosen because they are often used in research on known autoimmune diseases.

The researchers also measured levels of two brain autoantibodies (antibodies to brain tissue).  One, anti-MBP, is an antibody to myelin basic protein, a protein found in the protective sheaths around nerve fibers in the brain. The other, anti-NAFP, is an antibody to neuron-axon filament protein, a protein that makes up the nerve fibers themselves.