• Question: Is it possible to have bacteria that cause disease living in your body without you getting the disease/showing any symptoms of the disease?

    Asked by to Bethany, Hannah, Keith, Peter, Ramya on 20 Jun 2014. This question was also asked by .
    • Photo: Hannah Tanner

      Hannah Tanner answered on 20 Jun 2014:

      Yes this happens all the time!

      The bits of your body that are in contact with the outside have what we call normal flora. That is, good bacteria that live there without harming you. Your normal flora helps protect you from disease by stopping bad bacteria from taking up residence.

      Some bits of your body that don’t normally get exposed to the outside don’t have a normal flora. We call them sterile sites because sterile means free from bacteria and other micro-organisms.

      If you damage your skin, bacteria from your own body get get from the places where they normally are into the bits of you that should be sterile. This can cause an infection. The classic example of this is that about 30% of people carry Staphylococcus aureus up their nose (I’m not sure why it likes to live up noses) and on their skin. If you have some kind of cut to your skin either by accident or by surgery the Staphylococcus aureus from your skin can get into the wound and cause an infection despite the fact that you’ve had it harmlessly for ages. This is one of the reasons that skin has to be so thoroughly cleaned before surgery.

    • Photo: Bethany Dearlove

      Bethany Dearlove answered on 20 Jun 2014:

      Actually I disagree with Hannah here, as I would argue that bacteria that are part of your normal flora by definition don’t cause you any harm – as she says, they actually help you! But yes, it is possible to have bacteria in your body without you showing any symptoms. In some cases, no symptoms appear because your immune system has been extra efficient at clearing the infection – probably because you’ve had the disease before, and so your body knows how to deal with it.

      It’s also possible for bacteria to live in you without harm because they’re in the wrong environment. Staphylococcus aureus is found living quite happily in the nose of around 30% of people without them knowing, and generally won’t be a problem unless it manages to get in the blood stream. Another example is Clostridium difficile, a bacteria which will quite happily live in the gut with no problems. However, antibiotics for another infection (say, an ear infection) can kill off the protective good bacteria (normal flora) in the gut, allowing the C. difficile to take over and cause diarrhoea, with the possibility of more serious complications like damage to the bowel.

    • Photo: Peter Elliott

      Peter Elliott answered on 23 Jun 2014:

      To add to this I think I will go down a more immunological tunnel. There are around 7 billion people in the world each with their own version of an immune system. A bacterial infection can cause an infection response on the first two incidents of infection. After exposure to the same organism your body develops long term memory to prevent the infection from affecting you again so it is possible to become infected with a disease and for your immune system to remove the infection without you ever noticing.

      Also because of the variety of peoples immune system it is perfectly logical that some people are resistant to some bacteria compared to those around them. They might well become carriers, able to infect others, without actually becoming ill themselves.

      Returning to the previous answers, it is possible to harbour some infectious bacteria within your body, but your own “beneficial” flora can actually prevent the numbers of that infectious bacteria from reaching a point where disease actually occurs as Hannah says. Some of these “beneficial” bacteria can be opportunistic pathogens, what I mean is that for the most part they wont cause you any harm however, if there is a large change in the environment some of these bacteria can actually cause disease. For example in the gut you have many Campylobacter species which are mostly harmless but under sever stresses can infect you.

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