Normal Flora of Human Body

 

What is Normal flora?

Normal flora is define as harmless microorganisms routinely found growing on the body of a healthy individual. Normal flora are found on every part of your body that normally comes in contact with outside world (deep lungs and stomach are exceptions)

Note that not all normal flora is always harmless – normal flora includes opportunistic pathogens such as E. coli  which can cause urinary tract infections.

Normal Flora of Human Body

• Normal flora includes bacteria, fungi.
• Most areas of the body in contact with the outside environment harbor resident microbes; large intestine has the highest numbers of bacteria.
• Internal organs and tissues and fluids are microbe-free e.g. blood, brain, muscle, etc., are normally free of microorganisms. 
• Bacterial flora benefit host by preventing overgrowth of harmful microbes – microbial antagonism.

• Normal flora can be transient or permanent (“transient” or “resident”)

Initial Colonization of the Newborn

Uterus and its contents are normally sterile and remain so until just before birth.

Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be normal flora.

Associations Between Humans and the Normal Flora 

Host and bacteria are thought to derive benefit from each other.

The normal flora derive from their host:

1.a steady supply of nutrients

2.  a stable environment.

3. and protection and transport.

Human benefits from Normal flora

The host obtains from the normal flora certain nutritional and digestive benefits. 

1. Vitamin K and Vitamin B12, and lactic acid stimulation of the development  activity of immune system. 
2.  protection against colonization and infection by pathogenic microbes.

Harmful effect of Normal flora to Humans 

While most of the activities of the normal flora benefit their host, some of the normal flora are parasitic (live at the expense of their host), and some are pathogenic (capable of producing disease). Diseases that are produced by the normal flora in their host may be called endogenous diseases.

Most endogenous bacterial diseases are opportunistic infections, meaning that the organism must be given a special opportunity of weakness or let-down in the host defenses in order to infect. 

• An example of an opportunistic infection is chronic bronchitis in smokers where in normal flora bacteria are able to invade the weakened lung.
• Change the site of normal flora can cause an infection.
• Immunosuppressant patient is susceptible infection with normal flora.
• Use of broad spectrum antibiotic lead to diarrhea .