Probiotics and Clinical Disease

A few weeks ago, I went to an interesting lecture entitled, “Bacterial Colonization, Probiotics, and Clinical Disease” given by Allan Walker. The lecture focused on the hygiene hypothesis and the colonization of gut bacteria in children. Dr. Walker pointed that the colonization of bacteria in a person’s body occurs in four steps after leaving the germ-free in utero environment. The first exposure to bacteria is from a person’s mother while leaving the birth canal, the second round of exposure arises from oral feeding, the third from weaning, and the fourth phase is complete around the age of 2 years when the baby has complete adult colonization. Breast feeding and normal vaginal birth both help promote this bacterial colonization and can help against abnormal colonization that may lead to increased susceptibility to pathogens and immune mediated disease. It is apparent that a disruption in any of these steps may lead to a disruption in bacterial exposure during childhood development.

He highlighted many previous studies that have demonstrated the relationship between bacterial colonization and clinical disease. For example a study in Japan demonstrated that antibiotic use during infancy promotes a shift in the Th1/Th2 balance towards a Th2 dominant immunity in mice[1]. He also highlighted the importance of breast milk in promoting a normal pH and presence of normal intestinal flora. He argued that bacterial colonization helps promote a health host defense and that imbalances in T helper cells may lead to disease.

Through his description of countless studies that have examined the relationship of innate immunity and the presence of old friends, I was most interested in his research in probiotic treatment for clinical disease. He discussed that it may be possible to address the hygiene hypothesis by using probiotics as a surrogate for initial colonization and therapy for prevention and treatment of microbial-induced disease. I did not have much knowledge about probiotics but a simple google search yielded over two million matches, so it seems that they are certainly a hot topic. Probiotics are viable microbial dietary supplements used in fermented foods like yogurt and they claim to enhance natural defenses and prevent disease. You can by these in capsules in the supplement aisle and there are many dairy products that tout their probiotic qualities (such as Activia). Studies have shown that oral probiotics reduce the incidence and severity of necrotizing enterocolitis in very low birth weight infants[2]. However, clinical recommendations for probiotics are very much in the early stages, and Walker’s final conclusions stated that although probiotics may be a useful tool, many additional studies should be conducted to understand the specific function in clinical treatment.

[1] J Allergy Clin Immunol. 2001; 107(1):153-9
[2] Pediatrics 2005; 115; 1-4

For those of you interested in background of Probiotics
http://www.mayoclinic.com/health/probiotics/AN00389
http://www.msnbc.msn.com/id/27454348/ (mainstream article on MSNBC on probiotics in the news)
http://en.wikipedia.org/wiki/Probiotic (I know this is wiki, but it had an interesting history of their use, take it as a wiki source)

I addition I have the biliography from the lecture. If you are interested, let me know and I can scan/e-mail to you.