Should we live in a sterile world?

Kevin Donato
23 January 2012

Above: Image © Public Domain

Winter is officially here, and we are trying to stay away from germs that make us sick; so finish washing your hands and read on.

What if I told you that you were like a neighborhood? It sounds peculiar to be referred to as something that houses many residents. But only your residents aren’t people, they are microorganisms, especially bacteria — and you are a cozy home to them!

Our lifestyles are engaged in an escalating "antimicrobial arms race", including antibiotics and disinfectant cleaners we use. However, the majority of the bacteria we live with are actually helpful for maintaining our health.

Did You Know? The number of microbes that live in your digestive system vary on the order of 10 to 100 trillion organisms. They outnumber your own cells by 10 to 1!

The idea that we live in a beneficial co-existence with bacteria is an idea posed by biologists like Louis Pasteur and Elie Metchnikoff over 100 years ago. These bacteria, often referred to as being part of our "commensal microflora", help our body digest the food we eat to supply us with vitamins and nutrients that we cannot otherwise make and absorb on our own.

When we "evict" bacteria from our bodies, like when taking antibiotics to treat infections, we may do more harm than good. It is because the commensal microflora that normally live within us become greatly decreased in number — like ridding your friendly neighborhood of the good citizens that protect you. It is then that disease-causing "opportunistic" bacteria move in, such as Clostridium difficile, which causes outbreaks in hospitals. In some cases, antibiotic treatment can cause infectious bacteria, such as Escherichia coli (found in contaminated water and beef in Canada and the United States), to release potentially lethal toxins.

Salmonella growing on agar
Salmonella growing on agar ( Graham Beards, Wikimedia Commons

Did You Know? The different strains of bacteria that live within your digestive tract have a great impact on your overall health.

Bacteria known as "probiotics" are available in grocery and nutritional supplements stores. The World Health Organization and the Food and Drug Administration broadly define probiotics as microorganisms that benefit their host and are generally regarded as safe for consumption. Despite some advertising you may have seen claiming their helpful properties, scientific research has only just begun to decipher the ways in which they might prevent harmful infections, decrease inflammation, and contribute to our digestive health.

So even though you might not feel them wriggling inside your gut, there are plenty of helpful microbes taking care of you. Treat them well.

Learn More!

To learn more about microbiology and its applications visit Microbeworld


  • Research on the commensal microflora
  • WHO publication on probiotics
  • Wong CS, Jelacic S, Habeeb RL, Watkins SL and Tarr PI. 2000.The Risk of the Hemolytic–Uremic Syndrome after Antibiotic Treatment of Escherichia coli O157:H7 Infections. The New England Journal of Medicine. 342:1930-1936.
  • Kelly CP and LaMont JT. 2008. Clostridium difficile — More Difficult than Ever. The New England Journal of Medicine. 359:1932-1940.
  • Sherman PM, Ossa JC and Johnson-Henry KC. 2009. Unraveling Mechanisms of Action of Probiotics. Nutrition in Clinical Practice. 24:10-14.
  • Round JL and Mazmanian SK. 2009. The Gut Microbiota Shapes Intestinal Immune Responses During Health and Disease. Nature Reviews Immunology. 9:313-323.

Article first published December 6, 2009.

Kevin Donato

- Currently a Scientific Evaluator at the Marketed Pharmaceuticals and Medical Devices Bureau, Health Canada
  • Investigates suspected adverse reactions from medicines, and the ways to communicate and minimize the risk of these adverse events

- PhD, University of Toronto, Department of Laboratory Medicine and Pathobiology (2010)

  • research focused on studying the ways in which life-threatening bacteria and beneficial probiotics interact with our digestive tract 

- Has a passion for teaching science to diverse audiences, from kindergarteners to professionals, and has applied this interest during his
experiences as a science tutor and as a product development consultant

- Enjoys sailing, travelling, and culinary arts, when outside the office

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