Question: how does your body tell if you have bacteria in the body and how does it fight it off?

Michael Loughlin answered on 24 Jun 2010:

well we all have at least 1kg of bacteria in our colon alone so lots of bacteria get in our body and we never know ( apart from being able to digest food properly and not get intestinal infections all the time..i loathe the phrase friendly bacteria…but they are useful in stopping other bacteria invading)

so how do we know if bacteria are in …well if they get inthrough a breach we get inflammation which is where the body ships white blood cells to the site of infection as fast as it can. This is the swelling arounfd a cut..the sore bit.
Often inflammation causes at least as much damage , if not more, than the invading bacteria

any inflammation causes a disease ending in -itis so endocarditis is infamtion of the heart…bacteria got there somehow ( surgery often) we respond by send immune cells in ..this inflames the heart. Rash on the skin dermatitis…side of the eye conjunctivitis…intestines is gastroenteritis, gingivitis..gums lungs is pneumonia…whcih doesn’t fit..but you see what i mean

so lots of illnesses are inflammations of the X due to bacteria or other things getting to X and the body trying to get rid of them

bit more on recognition cos i worked on this a little
.The body recognises the bacteria are around…say the intestine.
Intestine cells send flare like warning chemicals called cytokines that attract the immune cells carried in fluid ( hence the swelling round a wound)
Now soem plases are more sensitive that others…if you got a flare sent up every time a bacteria met a gut cell you’d be constantly ill…so the really good receptors that reconise the bacteria are on the side of the cell that leads to the blood…a bacteria in there is far more dangerous so we get a much bigger response which have shown with gut cells and a bacteria called Campylobacter. ( campy causes gastroenteritis..leading to 3 days on the loo and 7lb weight loss…yes i do speak from expereince..though through a restaurant not the lab)
So if the bacteria hang around the body produces antibodies which basiclaly improve the killing of the bacteria…if its seen them before ( or vaccinated ) then the reposnse is bigger…
so while all this is going on you might be given antibiotics..which won’t kill all the bacteria but will reduce them in numbers so helping the immune system finish them off

lots of other ways to fight off bacteria..lings have cells that push bacteria back out..our tears can kill MRSA, our sweat makes are skin salty which many bacteria cannot stand…lots of different things

here’s a link i liked that covers a lot of ground
http://www.niaid.nih.gov/topics/immunesystem/pages/default.aspx
thanks for a great question..close to my heart