DIFFERENT TYPES OF MEDIA USED IN MICROBIOLOGY LAB - PharmaState Academy (2022)

Culture media contains nutrients and physical growth parameters necessary for microbial growth. All microorganisms cannot grow in a single culture medium and in fact many can’t grow in any known culture medium. Organisms that cannot grow in artificial culture medium are known as obligate parasites. Mycobacterium leprae, rickettsias, Chlamydias, and Treponema pallidumare obligate parasites.Bacterial culture media can be distinguished based on composition, consistency, and purpose.

CLASSIFICATION OF CULTURE MEDIA USED IN MICROBIOLOGY LABORATORY ON THE BASIS OF CONSISTENCY

  1. Solid medium: – Solid medium contains agarat a concentration of 1.5-2.0% or some other, mostly inert solidifying agent. Solid medium has physical structure and allows bacteria to grow in physically informative or useful ways (e.g. as colonies or in streaks).Solid medium is useful for isolating bacteria or for determining the colony characteristics of the isolate.
  2. Semisolid media: – They are prepared with agar at concentrations of 0.5% or less. They have soft custard like consistency and are useful for the cultivation of microaerophilic bacteria or for determination of bacterial motility.
  3. Liquid (Broth) medium: –
These media contain specific amounts of nutrients but don’t have trace of gelling agents such as gelatine or agar. Broth medium serves various purposes such as propagation of large number of organisms, fermentation studies, and various other tests. e.g. sugar fermentation tests, MR-VR broth.

CLASSIFICATION OF CULTURE MEDIA BASED ON THE BASIS OF COMPOSITION

  1. Synthetic or chemically defined medium: – A chemically defined medium is one prepared from purified ingredients and therefore whose exact position is known.
  2. Non-synthetic or chemically undefined medium: – Non-synthetic medium contains at least one component that is neither purified nor completely characterised nor even completely consistent from batch to batch. Often these are partially digested proteins from various organism sources. Nutrient broth, for example, is derived from cultures of yeasts.

CLASSIFICATION OF BACTERIAL CULTURE MEDIA BASED ON THE BASIS OF PURPOSE/ FUNCTIONAL USE/ APPLICATION

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Many special purpose media are needed to facilitate recognition, enumeration, and isolation of certain types of bacteria. To meet these needs, numerous media are available.

  1. General purpose media/ Basic media: – Basal media are basically simple media that supports most non-fastidious bacteria. Peptone water, nutrient broth and nutrient agar are considered as basal medium. These media are generally used for the primary isolation of microorganisms.
  2. Enriched medium (Added growth factors): – Addition of extra nutrients in the form of blood, serum, egg yolk etc, to basal medium makes them enriched media. Enriched media are used to grow nutritionally exacting (fastidious) bacteria. Blood agar, chocolate agar, Loeffler’s serum slope etc are few of the enriched media. Blood agar is prepared by adding 5-10% (by volume) blood to a blood agar base. Chocolate agar is also known as heated blood agar or lysed blood agar.
  3. Selective and enrichment media: – They are designed to inhibit unwanted commensal or contaminating bacteria and help to recover pathogen from a mixture of bacteria. While selective media are agar based, enrichment media are liquid in consistency. Both these media serve the same purpose. Any agar media can be made selective by addition of certain inhibitory agents that don’t affect the pathogen of interest. Various approaches to make a medium selective include addition of antibiotics, dyes, chemicals, alteration of pH or a combination of these. –Selective medium: – Differential growth suppression. Selective medium is designed to suppress the growth of some microorganisms while allowing the growth of others. Selective medium is agar based (solid) medium so that individual colonies may be isolated.

Examples of selective media include:

  • Thayer Martin Agar used to recover N. gonorrhoeae contains antibiotics; vancomycin, colistin and nystatin.
  • Mannitol Salt Agar and Salt Milk Agar used to recover S. aureus contains 10% NaCl.
  • Potassium tellurite medium used to recover C. diphtheriae contains 0.04% potassium tellurite.
  • MacConkey’s Agar used for Enterobacteriaceae members contains bile salt that inhibits most gram-positive bacteria.
  • Pseudogel Agar (Cetrimide Agar) used to recover P. aeruginosa contains cetrimide (antiseptic agent).
  • Crystal Violet Blood Agar used to recover S. pyogenes contains 0.0002% crystal violet.
  • Lowenstein Jensen Medium used to recover M. tuberculosis is made selective by incorporating malachite green.
  • Wilson and Blair’s Agar for recovering S. typhi is rendered selective by the addition of dye brilliant green.
  • Selective media such as TCBS Agar used for isolating V. cholerae from faecal specimens have elevated pH (8.5-8.6), which inhibits most other bacteria. –Enrichment culture medium: –Enrichment medium is used to increase the relative concentration of certain microorganisms in the culture prior to plating on solid selective medium. Unlike selective media, enrichment culture is typically used as broth medium. Enrichment media are liquid media that also serves to inhibit commensals in the clinical specimen. Selenite F broth, tetrathionate broth and alkaline peptone water (APW) are used to recover pathogens from faecal specimens.
  1. Differential/ indicator medium: – Certain media are designed in such a way that different bacteria can be recognised on the basis of their colony colour. Various approaches include incorporation of dyes, metabolic substrates etc, so that those bacteria that utilise them appear as differently coloured colonies. Such media are called differential media or indicator media. Differential media allow the growth of more than one microorganism of interest but with morphologically distinguishable colonies.

Examples of differential media include:

  • Mannitol salts agar (mannitol fermentation = yellow)
  • Blood agar (various kinds of haemolysis i.e. α, β and γ haemolysis)
  • Mac Conkey agar (lactose fermenters, pink colonies whereas non- lactose fermenter produces pale or colourless colonies.
  • TCBS (Vibrio cholerae produces yellow colonies due to fermentation of sucrose)
  1. Transport media: – Clinical specimens must be transported to the laboratory immediately after collection to prevent overgrowth of contaminating organisms or commensals. This can be achieved by using transport media. Such media prevent drying (desiccation) of specimen, maintain the pathogen to commensal ratio and inhibit overgrowth of unwanted bacteria. Some of these media (Stuart’s & Amie’s) are semi-solid in consistency. Addition of charcoal serves to neutralize inhibitory factors.

* Cary Blair transport medium and Venkatraman Ramakrishnan (VR) medium are used to transport faeces from suspected cholera patients.

* Sach’s buffered glycerol saline is used to transport faeces from patients suspected to be suffering from bacillary dysentery.

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* Pike’s medium is used to transport streptococci from throat specimens.

  1. Anaerobic media:Anaerobic bacteria need special media for growth because they need low oxygen content, reduced oxidation –reduction potential and extra nutrients.

Media for anaerobes may have to be supplemented with nutrients like hemin and vitamin K. Such media may also have to be reduced by physical or chemical means. Boiling the medium serves to expel any dissolved oxygen. Addition of 1% glucose, 0.1% thioglycollate, 0.1% ascorbic acid, 0.05% cysteine or red hot iron filings can render a medium reduced. Before use the medium must be boiled in water bath to expel any dissolved oxygen and then sealed with sterile liquid paraffin.

Robertson Cooked Meat (RCM) medium that is commonly used to grow Clostridium species contains a 2.5 cm column of bullock heart meat and 15 ml of nutrient broth. Thioglycollate broth contains sodium thioglycollate, glucose, cystine, yeast extract and casein hydrolysate.

Methylene blue or resazurin is an oxidation-reduction potential indicator that is incorporated in the medium. Under reduced condition, methylene blue is colourless.

  1. Assay media: – These media are used for the assay of vitamins, amino acids and antibiotics. E.g. antibiotic assay media are used for determining antibiotic potency by the microbiological assay technique.
Other types of medium include

* Media for enumeration of Bacteria,

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* Media for characterisation of Bacteria,

* Maintenance media etc.

FIND MORE AT…

Reference links

https://microbiologyinfo.com/list-of-culture-media-used-in-microbiology-with-their-uses/

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https://www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/culturing-microorganisms-6/culturing-bacteria-58/culture-media-364-5325/

https://www.google.co.in/amp/microbeonline.com/types-of-bacteriological-culture-medium/amp/

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FAQs

What are different types of media in microbiology? ›

These are classified into six types: (1) Basal media, (2) Enriched media, (3) Selective (4) Indicator media, (5) Transport media, and (6) Storage media.

What is basic media in microbiology? ›

The basic media contains a source of carbon & energy, nitrogen source, growth factors, and some trace elements. Some commonly used media components include peptone, agar, water, casein hydrolysate, malt extract, meat extract, and yeast extract. In addition, the pH of the medium should be set accordingly.

Why are different media needed in microbiology? ›

Differential media (or indicator media) in microbiology contain substances that lead colonies of certain organisms to take on a distinctive appearance. These media thus allow the microbiologist to differentiate various kinds of microorganisms on the same agar plate. An example of differential media is blood agar.

What is the different types of media? ›

The three types of media are commonly known as news media, social media, and web media, but you might also see them referred to as earned media, shared media, and owned media. Some other forms of modern media are print media, television, movies, and video games.

What are the 3 types of bacterial culture media? ›

Media can be classified as simple, complex and synthetic (or defined). Those bacteria that are able to grow with minimal requirements are said to non- fastidious and those that require extra nutrients are said to be fastidious. Simple media such as peptone water, nutrient agar can support most non-fastidious bacteria.

What are the three forms of laboratory media? ›

solid, semisolid, and liquid.

What is a medium in microbiology? ›

Slide 1 of 7. A microbial culture medium is a mixture of substances that promotes and supports the growth and differentiation of microorganisms. Culture media contain nutrients, energy sources, growth-promoting factors, minerals, metals, buffer salts, and gelling agents (for solid media).

How is media prepared in microbiology lab? ›

Media Prep - YouTube

Which media is used for bacterial growth? ›

An example of a selective medium is MacConkey agar. It contains bile salts and crystal violet, which interfere with the growth of many gram-positive bacteria and favor the growth of gram-negative bacteria, particularly the Enterobacteriaceae family.

Which agar is used for culture? ›

Fungal media

Sabouraud agar is used to culture fungi and has a low pH that inhibits the growth of most bacteria; it also contains the antibiotic gentamicin to specifically inhibit the growth of Gram-negative bacteria.

What type of media is MacConkey? ›

MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation.

Why is MacConkey Agar differential? ›

Based on the ability to ferment lactose, different species will yield colonies in varying appearance on a MacConkey medium. This gives McConkey agar its differentiating property.

Which media is used for isolation of bacteria? ›

Uses of Culture Media
Name of the MediaPrimary Purpose
Phenylethyl alcohol (PEA) agarSelective isolation of gram-positive and anaerobic gram-negative bacilli
Salmonella-Shigella AgarSelective for the isolation of Salmonella and Shigella spp.
Selenite brothUsed for the enrichment and isolation of Salmonella spp.
24 more rows
Jul 8, 2022

What are 10 types of media? ›

Here is the essential information about the main types of mass media and their political contents.
  • Newspapers. The core of the mass media of the departed twentieth century was the newspaper. ...
  • Magazines. ...
  • Television. ...
  • Public Broadcasting. ...
  • Commercial Radio. ...
  • Music. ...
  • Films. ...
  • Books.

What are the 8 types of media? ›

Modern media comes in many different formats, including print media (books, magazines, newspapers), television, movies, video games, music, cell phones, various kinds of software, and the Internet.

What are the different culture media and their uses? ›

List of culture media used in microbiology with their uses
MediaUses
· Mueller-Hinton AgarPerforming antimicrobial susceptibility for bacteria
· Nutrient Agar (1% to 2% Agar)Basal media in microbiology Supports the growth of all non-fastidious organisms
· Non-Nutrient AgarCultivation of parasites (e.g., Acanthamoeba)
57 more rows
Oct 26, 2018

What is the most commonly used agar? ›

Nutrient agar is a nutrient medium most effectively used for the cultivation of microorganisms supporting growth of a wide range of nonfastidious organisms, and blood agar is most appropriate for human-related organisms, in clinical practice.

What are 2 types of mediums for growing microbes? ›

The most common growth media for microorganisms are nutrient broths and agar plates; specialized media are sometimes required for microorganism and cell culture growth. Some organisms, termed fastidious organisms, require specialized environments due to complex nutritional requirements.

What are the three forms of laboratory media? ›

solid, semisolid, and liquid.

What are the types of cell culture media? ›

What are the different types of cell culture media?
  • Biological fluids: Examples include serum, plasma, lymph, and amniotic fluid.
  • Tissue extracts: Examples include embryo, bone marrow, tumour, and liver extracts.
  • Clots or coagulants: Examples include plasma clots and coagulants.
Mar 2, 2020

What are the different culture media and their uses? ›

List of culture media used in microbiology with their uses
MediaUses
· Mueller-Hinton AgarPerforming antimicrobial susceptibility for bacteria
· Nutrient Agar (1% to 2% Agar)Basal media in microbiology Supports the growth of all non-fastidious organisms
· Non-Nutrient AgarCultivation of parasites (e.g., Acanthamoeba)
57 more rows
Oct 26, 2018

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