How do bacteria cause disease in humans?
The first thing the bacterium has to do is enter your system. We come into contact with millions of bacteria every day. They are in the air we breathe, in and on the food we eat and on the surfaces of most things we touch. Apart from our normal flora, bacteria that come into contact with us have to pass our various defence mechanisms, our dry skin and our acid stomach. Physical actions such as the movement of matter through our alimentary canal, brushing our teeth and washing all help to make life difficult for bacteria. Those bacteria which do colonise our system generally do so by breaking through the mucus barrier that lines most of our alimentary canal (mouth to anus), or entering through damaged tissue, ie wounds and bites, etc. Once a bacterium has entered the system it is free to grow and spread – nearly all infectious diseases start out as small localised infections and will only spread through the system if the bacteria gain access to the blood stream. Infection simply means t
