Another Method: Destroying the Enemy by Another Enemy

There are many other micro-organisms that live within the human body which cause us no harm. What are these organisms that continue with their own life without doing us any harm, and what is their purpose in living within our body?

These groups of micro-organisms, which are gathered in certain parts of the body, are called the normal microbial flora of the body. They do no damage and even have some benefits for the human body. 

These micro-organisms provide external support for the defence army against microbes. They benefit the body by preventing foreign microbes from settling in it, because the entry of any microbe into the body is a threat to their own housing site. Since they do not want to be displaced by the invaders, they fight a fierce battle against them. We can think of these micro-organisms as "professional soldiers" fighting for the body. They try to protect the site they live in for their own benefit. In so doing, they complement the fully equipped army in our body. 

How do these "professional soldiers" settle in our bodies?

The human embryo has met no enemy during the gestation period in the mother's womb. Following the birth of the child, it makes contact with the environment, and numerous microbes are introduced to the child through the intake of food and by way of the respiratory tract. Some of these microbes die right away, while others are discharged before having the chance to settle down in the body. Some, however, settle in various parts of the body such as the skin, skin ridges, mouth, nose, eyes, upper respiratory tract, digestive tract, and genital organs. These microbes form permanent colonies at these locations and constitute the microbial flora of the human body.