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Differential medium types are those that distinguish microorganisms from one another based on growth characteristics evident when grown on specific medium types. Organisms with differing growth characteristics typically show visible differences in growth when placed on differential media. Examples include blood agar, Eosin Methylene Blue (EMB) agar, Mannitol Salt agar, and MacConkey agar.
Selective medium types are formulated to support the growth of one group of organisms, but inhibit the growth of another. These media contain antimicrobials, dyes, or alcohol to inhibit the growth of the organisms not targeted for study. Selective medium types include EMB agar, Mannitol Salt agar, MacConkey agar, and Phenylethyl Alcohol (PEA) agar.
Selective medium allow only the growth of some types of micro-organisms and inhibit the growth of undesirable or unwanted microorganisms. To this we add the elements that makes this selection
according to the characteristics of the microorganism sought. These media are used for the analysis of a sample polymycrobien.
Examples of selective media:
Sabouraud medium: it allows the growth of fungi./ Salmonella-Shigella medium / etc...
differential medium distinguishes two types of microorganisms growing in the same medium . This type of medium highlights certain biochemical characteristics of the microorganisms ( mainly the ability to degrade a substrate ) in the presence of indicator (s ) of the chemical reaction : colored indicators of pH or oxidation-reduction
examples of the differential media :
- BCP bromocresol purple differentiating lactose degradation .( lactose+ or lactose -)
-Agar Eosin Methylene Blue (EMB ) , which differs the lactose fermentation of sucrose
-MacConkey agar (MCK ) , differentiates the fermentation of lactose . Moreover, this is selective agar to the extent that it allows the growth of Gram -negative bacilli .
Selective and differential media are used to isolate or identify particular organisms. Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms. The selectivity is accomplished in several ways. For example, organisms that can utilize a given sugar are easily screened by making that sugar the only carbon source in the medium. On the other hand, selective inhibition of some types of microorganisms can be achieved by adding dyes, antibiotics, salts or specific inhibitors which affect the metabolism or enzyme systems of the organisms. For example, media containing potassium tellurite, sodium azide or thallium acetate (at concentrations of0.1 -0.5 g/l) will inhibit the growth of Gram-negative bacteria. Media supplemented with penicillin (5-50 units/ml) or crystal violet (2 mg/l) will inhibit the growth of Gram-positive bacteria. Tellurite agar, therefore, is used to select for Gram-positive organisms, and nutrient agar supplemented with penicillin can be used to select for Gram- negative organisms.
Differential media are used to differentiate closely related organisms or groups of organisms. Owing to the presence of certain dyes or chemicals in the media, the organisms will produce characteristic changes or growth patterns that are used for identification or differentiation. A variety of selective and differential media are used in medical, diagnostic and water pollution laboratories, and in food and dairy laboratories.
Selective media allows the selection of a group of organisms but not others. Examples are: McConkey Agar, Blood Agar, Mannitol Salt Agar, and EMB. While differential media is used in order to differentiate between closely related organisms. Examples are: McConkey, Blood, and EMB Agars.
Selective media inhibit the growth of certain bacteria and allow for the growth of others.This permits the isolation of desired bacteria in pure subcultures.An example of a selective media is Coulmbia CNA Agar which contains two antibiotics: Colistin and Nalidixic acid to inhibit Gram negative bacteria, leaving only the GRAM POSITIVES to grow. So it SELECTS the Gram positive bacteria. Differential media on the other hand, may allow many types of bacteria to grow, however, they permit desired types of bacteria to be DIFFERENTIATED after growth.An example is Mannitol salt agar(MSA).This media permits Staph.aureus species to show yellow colonies due to their fermentaion of7.5percent mannitol salt. This yellow colour differentiates the staph aureus from other colonies in the medium. A culture media can be both selective and differential. example: Maconkey selects the growth of Gram negative bacteria, and also differentiates the lactose-fermenting, from the non-lactose fermenting enterobacteria.
selective meium is the meium which grows only selective bacterias which are neeed and inhibits the others eg. MacConkey grows only gram negative bacterias and inhibits gram positive
Differential media are widely used for differentiating closely related organisms or groups of organisms. Because of the presence of certain dyes or chemicals in the media, the organisms will produce certain characteristic changes or growth patterns that are used for identification or differentiation of microorganism.
selective media used according to type of bacteria
Selective media favor the growth of some microorganisms while inhibiting others. Differential media help distinguish bacteria by the color of the colonies or the change in the medium
Media that inhibit the growth of other microorganisms and support the growth of the organism of interest are called selective media.selective medium contain particular ingredients that inhibit the growth of certain microbes .
example of selective media is Maconkey agar Tellurite blood agar selective medium for corynebacterium diptheriae .
Differential media contain compounds that allow groups of microorganisms to be visually distanguished the presence of certain dyes or chemicals in the media .
EMB agar is a differential medium used for the detection and isolation of gram negative intestinal pathogen XLD is also a differential medium .
MacConkey Agar. MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms.
