Tag: Types of culture media-classification

Types of culture media-classification

Types of culture media-classification


Types of culture media

  • The food material or substances required for growing microorganisms in vitro (outside the body) is called culture medium.
  • It is important to grow microorganisms outside the body for the following purposes:

1. to identify the cause of infection from the clinical sample, so that proper treatment can be given.

2. to study the characteristics or properties of microorganisms.

3. to prepare biological products like vaccines, toxoides, antigens…etc.

Types of culture media

I. Classification based on physical state 

    a) solid medium b) semi solid medium c) liquid medium

II. Classification based on the ingredients 

    a) simple medium b) complex medium c) synthetic or defined medium d) Special media

III-Classification based on physical state

  • Solid medium agar is the most commonly used solidifying agent.
  • Semi-solid media Such media are soft and are useful in demonstrating bacterial motility and separating motile from non- motile strains .
  • Liquid media are sometimes referred as “ broth “. bacteria grow uniformly producing general turbidity eg. Nutrient broth

IV-Classification based on the ingredients 

  1. Simple media – eg: Nutrient broth, N. agar – NB consists of peptone, meat extract, NaCl, – NB + 2% agar = Nutrient agar
  2. Special media :-  Enriched media • Selective media • Differential media • Transport media • Anaerobic media

a) Enriched media • Substances like blood, serum, egg are added to the simple medium. • Used to grow bacteria that are exacting in their nutritional needs. • eg: Blood agar, Chocolate agar, Blood agar BAP contains mammalian blood(usually sheep or horse) typically at a concentration of 5-10%, used to isolate fastidious organisms and detect hemolysis. Chocolate agar contain red blood cells that have been lysed by slowly heating to 80 c .and it used for growing fastidious bacteria, such as Haemophilus influenzae.

b) Selective media • The inhibitory substance is added to a solid media to inhibit commensal or contaminating bacteria such as : • Antibiotics • Dyes • Chemicals • Alteration of pH

Examples 

i) Thayer Martin medium selective for Neisseria gonorrhoeae → It usually contains the following combination of antibiotics:

  1. Vancomycin: which is able to kill most Gram-positive organisms.
  2. Colistin,: which is added to kill most Gram-negative organisms except Neisseria.
  3. Nystatin,: which can kill most fungi
  4. Trimethoprim: which inhibits Gram-negative organisms, especially swarming Proteus.

ii)  Eosin methylene blue →   selective for gram negative bacteria

The dye methylene blue in the medium inhibit the growth of gram positive bacteria.

ii) Campylobacter agar →   Is used for isolation of Campylobacter jejuni from fecal or rectal swab. • Contain Bacteriological charcoal , Cefoperazone and Amphotericin B.

iii) Lowenstein –Jenson medium is solid medium used for Mycobacterium tuberculosis. • contain penicillin, nalidixic acid and malachite green to inhibit growth of gram positive and gram negative bacteria, in order to limit growth to Mycobacteria  species only.

c) Differential media  these are designed in such a way that different bacteria can be recognized on the basis of their colony color. • Dyes and metabolic substrates are incorporated so that those bacteria that utilize them appear as differently colored colonies. Examples: • MacConkey agar • CLED agar • TCBS agar • XLD agar

  1. MacConkey medium • Distinguish between lactose fermenters & non lactose fermenters. • Lactose fermenters – Pink colonies • Non lactose fermenters – colorless colonies

  2. Thiosulfate-citrate-bile salts-sucrose agar(TCBS) • highly selective for the isolation of V. cholerae and V. parahaemolyticus Yellow coloured (sucrose fermenting) colonies of Vibrio cholerae on TCBS agar.

  3. Cysteine Lactose Electrolyte Deficient Agar(CLED) • For cultivation of pathogen from urine specimen , inhibit swarming of proteus sp. CLED, serratia dfd

  4. Xylose Lysine Deoxycholate Agar(XLD) • Used for the recovery of Salmonella and Shigella species.

d) Transport media –> • Media used for transporting the samples. • Delicate organisms may not survive the time taken for transporting the specimen without a transport media. • Eg: – Stuart’s medium – Buffered glycerol saline

e) Anaerobic media • These media are used to grow anaerobic organisms. Eg: • Robertson’s cooked meat medium. • Thioglycolate broth medium.

Exam Important

  1. Simple media – eg: Nutrient broth, N. agar – NB consists of peptone, meat extract, NaCl, – NB + 2% agar = Nutrient agar
  2. Special media :-  Enriched media • Selective media • Differential media • Transport media • Anaerobic media
  3.  Thayer Martin medium selective for Neisseria gonorrhoeae
  4. Thiosulfate-citrate-bile salts-sucrose agar(TCBS) • highly selective for the isolation of V. cholerae and V. parahaemolyticus Yellow coloured (sucrose fermenting) colonies of Vibrio cholerae on TCBS agar.
  5. Xylose Lysine Deoxycholate Agar(XLD) • Used for the recovery of Salmonella and Shigella species.
Don’t Forget to Solve all the previous Year Question asked on Types of culture media-classification

Module Below Start Quiz

Types of culture media-classification

types of culture- classification

Q. 1 An outbreak of streptococcal pharyngitis has occured in a remote village. In order to carry out the epidemiological investigations of the outbreak it is necessary to perform the culture of the throat swab of the patients suffering from the disease. The transport media of choice would be –

 A

Salt mannitol media

 B

Pike’s media

 C

Stuart’s media

 D

Cary Blair media

Q. 1

An outbreak of streptococcal pharyngitis has occured in a remote village. In order to carry out the epidemiological investigations of the outbreak it is necessary to perform the culture of the throat swab of the patients suffering from the disease. The transport media of choice would be –

 A

Salt mannitol media

 B

Pike’s media

 C

Stuart’s media

 D

Cary Blair media

Ans. B

Explanation:

Ans. is ‘b’ i.e., Pike’s media
“For cultures, swabs should be collected under vision from the affected site and either plated immediately or sent to the laboratory in Pike’s medium (blood agar containing crystal violet and sodium azide)”.


Q. 2

Selective media for vibrio – 

 A

TCBS

 B

Stuart

 C

Skirrows

 D

MYPA

Q. 2

Selective media for vibrio – 

 A

TCBS

 B

Stuart

 C

Skirrows

 D

MYPA

Ans. A

Explanation:

Ans. is ‘a’ i.e., TCBS 


Q. 3

Selective media for N. gonorrhoeae –

 A

Thayer martin media

 B

Smith noguchi media

 C

Proskaur and Bech media

 D

Bordet gongue, media

Q. 3

Selective media for N. gonorrhoeae –

 A

Thayer martin media

 B

Smith noguchi media

 C

Proskaur and Bech media

 D

Bordet gongue, media

Ans. A

Explanation:

Ans. is ‘a’ i.e., Thayer martin media 


Q. 4

All selective media are correctly matched except ‑

 A

V cholerae – TCBS medium

 B

Pseudomonas – Cetrimide agar

 C

M tuberculosis – LJ medium

 D

Campylobacter – BCYE medium

Q. 4

All selective media are correctly matched except ‑

 A

V cholerae – TCBS medium

 B

Pseudomonas – Cetrimide agar

 C

M tuberculosis – LJ medium

 D

Campylobacter – BCYE medium

Ans. D

Explanation:

Ans. is ‘d’ i.e., Campylobacter – BCYE medium


Q. 5

Selective media for Pseudomonas ‑

 A

EMJH medium

 B

PALCAM agar

 C

PLET medium

 D

Cetrimide agar

Q. 5

Selective media for Pseudomonas ‑

 A

EMJH medium

 B

PALCAM agar

 C

PLET medium

 D

Cetrimide agar

Ans. D

Explanation:

Ans. is ‘d’ i.e., Cetrimide agar


Q. 6

Transport media for the bacteria shown in the photomicrograph below is ? 

 A

Alkaline peptone water.

 B

Cary – Blair medium.

 C

TC BS medium.


 D None of the above.

Q. 6

Transport media for the bacteria shown in the photomicrograph below is ? 

 A

Alkaline peptone water.

 B

Cary – Blair medium.

 C

TC BS medium.


 D None of the above.

Ans. B

Explanation:

Ans:B.)Cary-Blair medium.
The bacteria marked by a black arrow in the photomicrograph is Vibrio Cholera.
Transport media for vibrio cholerae is Cary-Blair medium.
Transport media for fecal specimens
Media appropriate for the transport of fecal specimens that are suspected to contain Shigella, Vibrio cholerae, or Salmonella (including serotype Typhi) specimens are:
1. Cary-Blair transport medium

  • High pH (8.4)
  • Medium of choice for transport and preservation of V. cholera
  • Cary-Blair transport medium can be used to transport many bacterial enteric pathogens, including Shigella, Salmonella, and Vibrio cholerae

2. Amies’and Staurt’s transport media

  • Acceptable for Shigella and Salmonella (including ser. Typhi), but they are inferior to Cary-Blair for transport of V. cholerae.

3. Alkaline peptone water

  • This medium may be used to transport V. cholerae, but this medium is inferior to Cary-Blair and should be used only when Cary-Blair medium is not available.
  • It should not be used if subculture will be delayed more than 6 hours from the time of collection, because other organisms will overgrow vibrios after 6 hours.

4. Buffered glycerol saline (BGS)

  • It’s a liquid medium which can be used for Shigella but this transport medium is unsuitable for transport of V. cholerae.



Q. 7

Selective media for TB bacilli is:

 A

NNN media

 B

Dorset media

 C

LJ media

 D

Nutrient agar

Q. 7

Selective media for TB bacilli is:

 A

NNN media

 B

Dorset media

 C

LJ media

 D

Nutrient agar

Ans. B:C

Explanation:

Ans. (b) and (c) Dorset media and LJ media

Solid

Liquid

Lowenstein Jensen media (most widely used) Dubos contain Tween 80
Dorset egg media Middle Brook’s
Loeffler’s media Proskauer and Beck’s
Pawlowsky media Sula’s and Sautan
  • Selective agent inhibiting other bacteria in LJ media is Malachite green.
  • Human tubercle bacilli do not grow in presence of para-nitrobenzoic acid.
  • Traces of fatty acid is toxic for tubercle bacilli in culture media.
  • Optimum pH for M. tuberculosis: 6.4-7.0.

Other Options:

NNN media → For Leishmania donovani

Nutrient agar → Simple media

MacConkey media → Differential as well as indicator media for lactose and non-lactose fermenters.


Q. 8

A patient with acute onset of diarrhea comes to emer­gency. After culture on enriched media, colonies as shown below were visualized. Identify the causative organism:

 A Vibrio cholera

 B

Salmonella typhi

 C

Compylolacter jejuni

 D

E. coli 

Q. 8

A patient with acute onset of diarrhea comes to emer­gency. After culture on enriched media, colonies as shown below were visualized. Identify the causative organism:

 A

Vibrio cholera

 B

Salmonella typhi

 C

Compylolacter jejuni

 D

E. coli 

Ans. A

Explanation:

Ans. is. ‘a’ i. e., Vibrio cholera



Malcare WordPress Security