Selective Media – Basic microbiology, parasitology, and immunology; nature, reproduction, growth, and transmission of common microorganisms and parasites in Bangladesh; prevention including universal precaution and immunization, control, sterilization, and disinfection; and specimen collections and examination. Students will have an understanding of common organisms and parasites caused human diseases and acquire knowledge about the prevention and control of those organisms.
Selective Media
The media which favour the growth of a particular desired bacterium by inhibiting the growth of undesired bacteria are known as selective media.
Example :
| Selective media | Desired bacteria | Selectivity maintainer |
| Mac Conkey’s agar media | Enterobacteriaceae. | Bile salt |
| Blood telluride agar medium | Corynebacterium diphtheria | K-tellurite |
| Lowenstein-Jensen media | Mycobacterium tuberculosis | Malachite green |
| TTGA (Tellurite Taurocholate Gelatine agar) or, Monsur’s media | Vibrio cholerae | Bile salt & K-tellurite |
| Deoxycholate citrate agar (DCA) | Shigella & Salmonella. | Na-deoxycholate Na- thiosulphate Ferric amino citrate. |
Definition of Enriched media
The media that are enriched usually by adding blood, serum or egg to support the growth of desired organism as they require, are known as enriched media.
Example :
| Enriched Media | Organism |
| Blood agar media |
|
| Chocolate agar media |
|
| Lowenstein-Jensen media |
|
Uses:
- To see the culture of specific organism.
Process of Formation of Enriched Media
When the special nutrients are added to basal media, the latter is converted to enriched media. The enriched substances are:
- Human blood.
- Sheep blood,
- Egg, and
- Serum.
Difference between Selective and Enriched Media
| Traits | Selective media | Enriched media |
| Definition | The media which favour the growth of a particular desired bacterium by inhibiting the growth of undesired bacteria are known as selective media | The media that are enriched usually by adding blood, serum or egg to support the growth of desired organism as they require, are known as enriched media. |
| Type | Selective media is always solid | Enriched media is always liquid |
| Example | Blood agar media Chocolate agar media | Mac Conkey’s agar media Blood tellurite agar medium |
Chocolate Agar Media is More Enriched than Blood Agar Media
Chocolate agar-media is more enriched than blood agar media, because, by applying heat to sheep blood, RBC is lysed and therefore extra nutrients within the RBC come out in the media and these nutrients are more readily available to bacteria.
Indicator/Differential Media
When an indicator is included in the medium for which a particular organism causes changes in the medium, is known as indicator media.
Example :
| Indicator media | Pathogen | Indicators |
| Mac Conkey’s agar media | Enterobacteriaceae | Neutral red & lactic acid; Lactose fermenting organisms produce pink colour, whereas nonlactose fermenting organisms produce pale colour. |
| Blood agar media | Streptococcus | RBC (lysis) |
| TTGA or Monsur’s media | Vibrio cholera | K-tellurite |
| Blood tellurite agar medium | Corynebacterium diphtheriae | lan K-tellurite |
| Deoxycholate citrate agar | Shigella & Salmonella | Neutral red & lactose |
Transport Media
They are used to transport specimen containing microorganisms from one place to distant ones.
Importance of transport media
These media are used when specimen can’t be cultured soon after collection.
Example :
- Cary-Blair medium for salmonella. Shigella, Vibrio.
- Amies medium -For gonococci & other pathogens.
- Monsur’s medium-For Vibrio cholerae
- Stuart’s transport media for gonococci.
- Alkaline peptone water – For Vibrio
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