Normal Flora and bacteria identification

The human body is naturally inhabited by millions and millions of microbes a big percent of these do not have pathogenicity to cause disease which is collectively referred to as normal flora. This experiment was performed to investigate the diversity of these microbes from different sites of the body, swabs were taken from the skin behind the ear and back of the throat using a wet cotton swap and were inoculated on both blood and mannitol salt agars, incubated for a period of 24-48 hour. Identification was done by describing the colony morphology, biochemical tests, cell morphology and gram staining.

And it was found that Staphylococcus aureus and Escherichia coli is most likely organisms isolated from skin and throat respectively. Introduction The human body is inhabited by a wide variety of microbes both internal and external. In a healthy human internal tissue are normally free of microorganisms whereas surface tissues are in constant contact with environmental organisms and become readily colonized by certain microbial species (Toddar 2005). The mixture of organisms regularly found at any anatomical site is referred to as the normal flora or normal biota.

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Each body surface has its own characteristic resident biota made up of particular microbial species (Ingraham & Ingraham, 2004). The type of bacteria found in a certain location depends on environmental needs such as ideal temperature, pH, physiology and available nutrients. For example, areas such as the armpit, navel or the back of the throat inhibits more microorganisms due to the favorable condition of increased moisture, body temperature and greater concentration of skin surface lipids (Baron 1996). Culturing of microbes into appropriate media has made it possible in the identification of various micro organisms.

Culture media provide an ideal condition which supports the growth of microbes. A number of these media are formulated in such away that they will ease the identification process. Among the many used media are the enrichment media which function to support the growth a number of organisms by providing an extra importance growth condition that will favors microbial growth. Blood agar is an example of enrichment media, but also it can be classified as a differential media when used to identify hemolytic bacteria as beta, alpha and gamma hemolytic bacteria, according to (Bauman, 2005).

Mannitol salt agar can be used as both differential and selective media; differential media give a distinctive appearance that distinguishes the colonies from the rest of the colonies by staining. While selective media contain inhibiting factors that suppress the growth of other species, but also contain specific favoring factors for a given species of bacteria, for example mannitol is selective media for non pathogenic Staphylococcus.

The aim of the experiment was to cultivate normal flora on the human skin and throat present using differential selective media and to identify specific group of bacteria from region obtained by observation of colonies and gram staining. Methods A sterile cotton tipped swap was used to swap gentle the Skin behind the ear by bending the ear lope. A sterile swap was used to swap on the back of the throat by allowing the patient to open mouth wide enough for the physician take a swap, with great care to avoid without contamination.

Streaking technique was applied by streaking across the surface of the solid agar to allow distribution of the organisms. The inoculums were incubated at 370c for 24 hours and were observed, by describing the morphology and appearance of the colonies and cells. Coagulase test was done on positive strains after an over night incubation in rabbit plasma which were inoculated using the same amount of inoculums along side controls formation of a clot indicate coagulase positive.

catalase test is done by placing the colony smear on a glass slide and adding few drops of hydrogen peroxide and observe for the present of bubbles which indicate catalase positive. Gram staining involves staining the bacteria with stain where by gram positive retain the dye after washing but gram negative do not retain the dye. Mannitol agar support the growth of gram positive bacteria and shows yellow color is a clear indication of lactose fermentors.

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