There are many ways and at many levels a microorganisms can interact with humans. Microorganisms regularly found at any anatomical site are collectively referred to as normal flora. The normal flora present in the body is highly complex and consists of more than 200 species of bacteria. The residency of normal flora depends upon several factors, including age, genetics, sex, nutrition and diet of the person. Therefore, humans have a mutualistic relationship with many of the microorganisms of their indigenous microflora. The normal flora is beneficial from the host a supply of a stable environment and constant temperature, nutrients, protection, and transport. Nutritional benefits, stimulation of the immune system, and colonization strategies are acquired by the host from the normal flora. The normal flora exhibits a tissue preference for colonization. This is referred to as tissue tropism. This is due to the host has the essential growth factor and nutrients for a particular microflora. Besides, the normal flora can specifically colonize to a particular tissue with capsules, fimbriae, and cell wall components. In addition, some of the indigenous bacteria are able to construct bacteria biofilms on a tissue surface. There are two types of normal flora found which are resident microflora and transient microflora. Resident microflora is defined as the organisms that are always present in the body while transient microflora is those present temporarily and under certain conditions.
Human is first colonized by a normal flora at the moment of birth and passage through the birth canal. A fetus has no normal flora. During and after delivery, a newborn is exposed to many microorganisms from its mother, food, air, and basically everything that in contact with the infants. The resident microflora of the skin consists of bacteria and fungi which is approximately 30 different types. The high amount of microorganisms can be found at moist and warm condition in hairy areas of the body where there are many sweat and oil glands, such as under the arms, the groin, moist folds between the toes and fingers. Whereas at dry, calloused areas of skin have fairly low amount of bacterial cells. The majority of skin microorganisms are found on the most superficial layers of the skin and upper part of the hair follicle. They consist of Staphylococcus epidermis and Micrococcus app and corynebacteria. These are considered as commensal ad generally nonpathogenic. However, pathogenic Staphylococcus aureus is found on the face and hands, particularly in individuals who are nasal carriers.
The respiratory tract can be divided into upper respiratory and the lower respiratory tract. The nares are mainly colonized, predominantly with Staphylococcus epidermis and corynebacteria with Straphylococcusaureas. The healthy sinuses, in contrast are sterile. The lower respiratory tract is usually free of microbes, mainly because of the efficient cleaning action of the ciliated epithelium which lines the tract. For the microflora in the conjunctiva, numbers of bacteria may be cultivated from the normal conjunctiva but the number of organisms is usually small. Staphylococcus epidermis and certain coryneforms are dominant. Staphylococcus aureus, some streptococci, Haemophilusspp. and Neisseria spp. are usually found. Blinking every second and lachrymal secretions give no opportunity for microorganisms to colonize the conjunctiva without special mechanisms to attach to the epithelial surfaces and the ability to withstand attack by lysozyme.
The presence of nutrients, epithelial debris, and secretions makes the mouth a favorable habitat for a great variety of bacteria. If dental hygiene is not taken care well, this will allows growth of these bacteria, with development of dental caries, gingivitis, and more severe periodontal disease. There are several microbes which have been isolated from healthy human mouths. It...