• Question from:Jonathan

The human body contains good bacteria but would I be wrong in saying that this bacteria can turn bad if something went wrong?


The immune system detects an infection and sends out white blood cells etc. to defeat it and protect the body, if this is successful the body would then become immune to the infection. Having said that, the body would then know the properties of that bacteria or virus or so forth.

My question is this, would the body's bacteria be able to evolve into bad infectious bacteria (with the information that the immune system has) then that could harm the body if something inside or outside the body happened. If this was possible, would this not be able to cause an infection in the body?

Photo
  • Barts and the London, London
  • Posts: 268

Yes bacteria can turn virulent by changes to the body.

An example from my own work: we have found and people before us have observed that people who smoke are more susceptible to catching pneumonia which is caused by a bacteria. This is because cigarette smoke changes gene expression in lung cells which makes them easier for pneumonia causing bacteria to infect. This same bacteria may be carried in the nasal cavity of people but won't cause pneumonia.

Now we're also looking at whether cigarette smoke causes the bacteria itself to change from non-disease causing to disease causing. Preliminary data has shown that yes it does!

Photo
  • University of Leeds, UK
  • Posts: 106

Yes, sometimes bacteria merely need to move to another part of the body, and have an opportunity to invade a space where they're not normally found. Many 'would-be' bad bacteria are kept in check by the many other bacteria that surround them, each competing and finding their place within a particular part of the body.

For example, one type of bacteria that lives in the back of the nose, Staphylococcus aureus, can be quite a capable pathogen (disease causer), and has an arsenal of weapons it can use to cause infection, but many of these abilities are suppressed by the high salt content of the nose (amongst other things). Moving from that environment into, say, an open wound following injury or an operation can present it with an opportunity to attack, with less of the control elements there.

Whilst it can keep a low profile away from your innate immune system in the nose, once it enters the cavity of the body it is recognised by the powerful adaptive immune system and in most cases is cleared. Obviously problems arise when the immune system or blood circulation is poor, or the strain is spectacularly virulent.