Microbiome – How trillions of microorganisms work to keep you healthy

What is the microbiome?


Orange circle graphic with text that reads "A healthy gut includes more than 1000 different types of bacteria, viruses and fungi."

Our microbiome is priceless to us

Our bodies contain more bacterial than human cells and genes

Image with text. An estimated 30 trillion cells in your body--less than a third--are human. The other 70-90% are bacterial and fungal. 99% of the unique genes in your body are bacterial. Only about 1% are human.
Source: https://www.amnh.org/explore/science-topics/microbiome-health/meet-your-microbiome

Helpful hints to strengthen your microbiome

The microbiome can become out of balance

The current evidence about probiotics

Special groups


Older Adults

Further information

Book: The Whole-Body Microbiome: How to Harness Microbes—Inside and Out—for Lifelong Health – Brett Finlay and Jessica M. Finlay (2019)

Book: B. Let Them Eat Dirt – B. Brett Finlay and Marie-Claire Arrieta (2016)

Film: Let Them Eat Dirt: The Hunt for Our Kids’ Missing Microbes (2019)


  1. Gilbert JA, Blaser MJ, Caporaso JG, Jansson JK, Lynch S V., Knight R. Current understanding of the human microbiome. Nat Med. 2018;24(4):392-400. doi:10.1038/nm.4517
  2. David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014;505(7484):559-563. doi:10.1038/nature12820
  3. Wu GD, Chen J, Hoffmann C, et al. Linking Long-Term Dietary Patternswith Gut Microbial Enterotypes. Science (80- ). 2011;334(October):105-109. doi:10.1126/science.1208344.
  4. Taylor BC, Lejzerowicz F, Poirel M, et al. Consumption of Fermented Foods Is Associated with Systematic Differences in the Gut Microbiome and Metabolome. mSystems. 2020;5(2). doi:10.1128/msystems.00901-19
  5. Leeuwendaal NK, Stanton C, O’toole PW, Beresford TP. Fermented Foods, Health and the Gut Microbiome. Nutrients. 2022;14(7):1-26. doi:10.3390/nu14071527
  6. Ortiz-Alvarez L, Xu H, Martinez-Tellez B. Influence of Exercise on the Human Gut Microbiota of Healthy Adults: A Systematic Review. Clin Transl Gastroenterol. 2020;11(2):e00126. doi:10.14309/ctg.0000000000000126
  7. Bonomini-Gnutzmann R, Plaza-Díaz J, Jorquera-Aguilera C, Rodríguez-Rodríguez A, Rodríguez-Rodríguez F. Effect of Intensity and Duration of Exercise on Gut Microbiota in Humans: A Systematic Review. Int J Environ Res Public Health. 2022;19(15). doi:10.3390/ijerph19159518
  8. Maillard JY, Pascoe M. Disinfectants and antiseptics: mechanisms of action and resistance. Nat Rev Microbiol. 2024;22(1):4-17. doi:10.1038/s41579-023-00958-3
  9. Yang QE, Ma X, Li M, et al. Evolution of triclosan resistance modulates bacterial permissiveness to multidrug resistance plasmids and phages. Nat Commun. 2024;15(1). doi:10.1038/s41467-024-48006-9
  10. Modi SR, Collins JJ, Relman DA. Antibiotics and the gut microbiota. J Clin Invest. 2014;124(10):4212-4218. doi:10.1172/JCI72333
  11. Brown KA, Khanafer N, Daneman N, Fisman DN. Meta-analysis of antibiotics and the risk of community-associated Clostridium difficile infection. Antimicrob Agents Chemother. 2013;57(5):2326-2332. doi:10.1128/AAC.02176-12
  12. Éliás AJ, Barna V, Patoni C, et al. Probiotic supplementation during antibiotic treatment is unjustified in maintaining the gut microbiome diversity: a systematic review and meta-analysis. BMC Med. 2023;21(1):1-18. doi:10.1186/s12916-023-02961-0
  13. Suez J, Zmora N, Zilberman-Schapira G, et al. Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT. Cell. 2018;174(6):1406-1423.e16. doi:10.1016/j.cell.2018.08.047
  14. Cunningham M, Azcarate-Peril MA, Barnard A, et al. Shaping the Future of Probiotics and Prebiotics. Trends Microbiol. 2021;29(8):667-685. doi:10.1016/j.tim.2021.01.003
  15. Fehr K, Moossavi S, Sbihi H, et al. Breastmilk Feeding Practices Are Associated with the Co-Occurrence of Bacteria in Mothers’ Milk and the Infant Gut: the CHILD Cohort Study. Cell Host Microbe. 2020;28(2):285-297.e4. doi:10.1016/j.chom.2020.06.009
  16. Donald K, Finlay BB. Early-life interactions between the microbiota and immune system: impact on immune system development and atopic disease. Nat Rev Immunol. 2023;23(11):735-748. doi:10.1038/s41577-023-00874-w
  17. Patrick DM, Sbihi H, Dai DLY, et al. Decreasing antibiotic use, the gut microbiota, and asthma incidence in children: evidence from population-based and prospective cohort studies. Lancet Respir Med. 2020;8(11):1094-1105. doi:10.1016/S2213-2600(20)30052-7
  18. Dai DLY, Petersen C, Hoskinson C, et al. Breastfeeding enrichment of B. longum subsp. infantis mitigates the effect of antibiotics on the microbiota and childhood asthma risk. Med. 2023;4(2):92-112.e5. doi:10.1016/j.medj.2022.12.002
  19. Bosco N, Noti M. The aging gut microbiome and its impact on host immunity. Genes Immun. 2021;22(5-6):289-303. doi:10.1038/s41435-021-00126-8

Antibiotic Resistance, Overuse and Misuse in Adults Over 65

Two older adults stand smiling. Test beside them reads "We're antibiotic wise. We learn about antibiotics so we can chat confidently with our doctor."

Misinformation about antibiotics leads to overuse, misuse and resistance

Antibiotics are the most common treatment for bacterial infections. They don’t work for viral infections like colds, flu or COVID-19. Antibiotic resistant bacteria develop if you take antibiotics when you don’t need them. When these bacteria spread, it undermines modern medicine.

Why should adults over 65 be concerned about antibiotic resistance?

If you are over 65 years of age you are more likely to have an infection. You may have a weakened immune system or live in a care home in close contact with others who may be ill.

As well, you may visit health care settings like hospitals more often. Infections can spread easily in these settings. Antibiotics may also interact with other medications you are already taking.

What you can do to prevent antibiotic resistance

  1.  If you are being prescribed antibiotics, ask your health-care provider about the best option for you. 
  2.  If prescribed antibiotics, discuss with your health-care provider side effects and interactions with other medications. 
  3.  Always follow your health-care provider’s directions on how to take antibiotics.

Reduce the spread of infections to help yourself and others. 

Reducing and preventing the spread of infections in the first place decreases the need for antibiotics, and will help us all to stay healthier.

  1. Wash your hands often with plain soap and water.
  2. Clean common surfaces with regular cleaner and water – you don’t need antibacterial cleaners for most home cleaning.
  3. Store, handle and prepare food safely.
  4. Sneeze into a sleeve or tissue to avoid spreading germs
  5. Stay active and develop healthy habits to keep your immune system strong.
  6. Stay home when you feel sick.
  7. Keep up to date on your vaccinations.


Antibiotics and Adults Over 65 – Brochure

Download the brochure to learn more about how adults over 65 can be more Antibiotic Wise.

Antibiotics and Adults Over 65 – Poster

Download and use the poster to raise awareness about issues related to antibiotics in adults over 65.

Penicillin Allergy – Things You Need to Know

Illustration of various colourful pills, with text overlay reading "Allergic to penicillin? Things you need to know."

What is penicillin?

Penicillin is one of the first antibiotics discovered, and has been used for nearly 80 years to treat common bacterial infections such as bronchitis and laryngitis. It is inexpensive and can treat skin, ear, sinus and upper respiratory tract infections.

Penicillin is one of the safer antibiotics

Compared to other antibiotics, penicillin can be more effective and less likely to result in antibiotic-resistant bacteria. It also has a lower risk of causing C. difficile infection, a severe and hard to treat diarrhea.

Do you have a penicillin allergy?

You may have had a reaction when taking penicillin in the past in the form of hives, itchiness, rashes or swelling. These are common side effects and do not necessarily indicate an allergy. Fewer than 5 in 10,000 people have a true penicillin allergy.

In fact, 80 per cent of adverse effects related to penicillin disappear over time. This means that you may be able to take penicillin safely again the next time you need it, even if you have had reactions to the antibiotic in the past.

Should you take penicillin? 

Always share any past penicillin reactions with your health-care provider. They will let you know if you should try penicillin again or use another antibiotic. While your health-care provider may avoid prescribing you penicillin, they may also determine that it is safe to try again.

This is important as the alternatives to penicillin are often stronger antibiotics which may have a higher risk of side effects and should be saved for times when they are truly needed. If these alternative antibiotics are used too much, bacteria may develop resistance to these drugs, and they may not work in future.

Penicillin allergy and what you can do

Before asking to be prescribed a different antibiotic, talk to your health-care provider. They will be able to evaluate your allergy or refer you to an allergist.


Allergic to Penicillin? Brochure

Download the brochure to learn about penicillin allergy, and how to be Antibiotic Wise.

Allergic to Penicillin? Poster

Download and use the poster to raise awareness about penicillin allergy.

Penicillin Allergy Fact Sheet

Did you know that half of all penicillin allergies go away within 5 years? Learn more about why penicillin may still be the right choice even if you have been told you have an allergy.

BC Women’s Penicillin Allergy Challenge Test

Fact sheet for a new initiative from the BC Women’s Hospital testing penicillin allergies of pregnant women.

Drop the Label Website

Patient and provider information on antibiotic allergies.

Using Antibacterial Products at Home

Image of man cleaning dining table with spray bottle and cloth. In the background, a teenager prepares food in the kitchen. Overlaid text reads: "Using antibacterial products at home? Things you need to know."

Using antibacterial products in your home washes away the good bacteria

Millions of good bacteria live on our bodies to protect against infections caused by bad bacteria. Good bacteria also keep harmful bacteria from multiplying. Antibacterial cleaners, makeup and body products wash away the good and the bad. Antibacterial use makes bacteria more resistant to antibiotics.

Using antibacterial products in your home impacts hospital disinfectants

Researchers have found little difference between using plain soap or antibacterial soap in a home or community setting and there is no added benefit of using antimicrobial soap in preventing infections. Similarly, antibacterial ingredients added to makeup, hygiene products, and surfaces of children’s toys have no added benefit to protect against the common cold or the flu. Moreover, some antimicrobial chemicals (such as Triclosan) are harmful to plants and animals when the chemicals are washed down the drain. Triclosan also kills good bacteria and can cause antibiotic resistance over time.

What household products may be labelled as antibacterial, antimicrobial or antiseptic?

What are alternatives to antibacterial products?

Plain soap or detergent and water (any temperature) are the only tools you need to get things clean. Most households don’t need antibacterial cleaning products. 

There’s little difference between plain soap versus antibacterial soap when you’re at home. Antibacterial ingredients don’t protect you better from cold or flu. Handwashing with plain soap is extremely effective at reducing the spread of germs.  


Safe Food Handling

BC Centre for Disease Control’s tips and guidelines on safe food handling to reduce risk of contamination and food poisoning.

Green Cleaning Product Recipes

The Queen of Green has developed 9 easy cleaning recipes for everyday cleaning.

Alternative Non-Toxic Disinfectants

The David Suzuki Foundation have provided alternative non-toxic disinfecting solutions for at-home use.

Antibiotics for Cold, Flu and COVID-19

Close-up image of woman blowing nose into a tissue, wearing a large scarf. Overlaid text reads "Antibiotics don't work against cold, flu and COVID-19. Thing you need to know."

Antibiotics for cold, flu and COVID-19 do not work

Antibiotics treat bacterial infections. Colds, COVID-19 and the flu are viral infections, so antibiotics won’t help. Using antibiotics when you have these illnesses can lead to the development of antibiotic resistant bacteria.

There are a few ways to help prevent colds, flu and COVID-19

How can I treat colds and the flu? 

The best way to recover from a cold or flu is to drink plenty of fluids, get rest, and give your body time to do its job.  

Do I have COVID-19?

If you experience any of these symptoms, stay home and contact your healthcare provider. You may just have a cold or the flu but stay home to keep others safe. Here is a link to the BC COVID-19 Self-assessment Tool

Symptoms of COVID-19 include new or worsening:

COVID-19 symptoms can range from mild to severe. Sometimes people with COVID-19 have mild illness, but their symptoms may suddenly worsen in a few days.

Go to an urgent care clinic or emergency department if you:


Antibiotics, Cold and Flu Video

Antibiotics treat bacterial infections and can be life-saving. But, antibiotics won’t kill viruses like cold and flu.

Say Naaah Poster

A poster suitable for doctor’s offices, community centres and other public locations. Open up and think twice about antibiotics.

Get a Flu Vaccine

Book a flu shot near you.

Choosing Wisely – Cold and Flu

Antibiotics don’t help most respiratory infections, and they can even be harmful. See ways you can help treat symptoms from colds and flu without unnecessary antibiotics.

Guide to Wise Use of Antibiotics

Booklet with information on antibiotics, antibiotic resistance, and managing common illnesses.

How to Wash Your Hands Poster

Poster with the six steps for proper hand washing.

Antibiotics and Dental Care – Things You Need to Know

Image of woman sitting in dentist chair, smiling at dentist. Overlaid text reads "Antibiotics and dentistry. Things you need to know."

You don’t always need antibiotics at the dentist

Antibiotics are appropriate for some dental procedures. They are used to prevent or fight infections, but many toothaches and oral infections do not need antibiotics. Discuss options with your dentist. Always tell your dentist about any medical conditions or health changes.

What are antibiotics for dental care?

Antibiotics are medicines for treating bacterial infections. They play a vital part in modern medicine and dentistry.

When taken incorrectly or overused, bacteria can develop resistance to antibiotics. This means antibiotics may not work the next time you need them. When antibiotics for serious bacterial infections stop working, lives are lost.

Antibiotics and Dental Care – How Can I Help? 

Maintaining a healthy dental routine helps prevent oral infections that require antibiotics. Eat well, brush, floss and visit your dentist regularly. These are all important steps in preventing dental disease.


Antibiotic Resistance Video

Sometimes you need antibiotics, but what if you don’t? When you use antibiotics too often or incorrectly, bacteria can develop resistance.

Preventing Infection Video

Antibiotics fight and prevent infection. They revolutionized modern dentistry. But there are other effective ways to prevent infection.

Antibiotics and Dental Care Fact Sheet

Learn more about the use of antibiotics in dental practice, and why they may not be needed for every condition.

Say Naah Poster

A poster suitable for dental offices, community centres and other public locations. Open up and think twice about antibiotics.

Your Dental Health Website

Your Dental Health is a public education program of the BC Dental Association (BCDA) providing general dental information.

Penicillin Allergy Fact Sheet

Did you know that half of all penicillin allergies go away within 5 years? Learn more about why penicillin may still be the right choice even if you have been told you have an allergy.

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