How do you make agar MSA?

Asked By: Hermelina Bakihanov | Last Updated: 26th March, 2020
Category: medical health infectious diseases
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Preparation of Mannitol Salt Agar (MSA)
  1. Suspend 111 grams of Mannitol Salt Agar in 1000 ml of distilled water.
  2. Boil to dissolve the medium completely.
  3. Sterilize by autoclaving at 15 lbs.
  4. If desired, sterile Egg Yolk Emulsion (E7899) can be added to a final concentration of 5% v/v after autoclaving.

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Similarly, it is asked, what does MSA agar test for?

Mannitol Salt Agar (MSA) is used as a selective and differential medium for the isolation and identification of Staphylococcus aureus from clinical and non-clinical specimens. It encourages the growth of a group of certain bacteria while inhibiting the growth of others.

Likewise, what Bacteria grows on MSA? Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol. Most non-pathogenic staphylococci will not ferment mannitol. The Staphylococcus aureus ferments mannitol and turns the medium yellow. The Serratia marcescens does not grow because of the high salt content.

Similarly, it is asked, which organisms did not grow on MSA plate?

Expected colony characteristics of organism in Mannitol Salt Agar

  • Escherichia coli: Does not grow.
  • Staphylococcus epidermidis: Colorless to pink colonies.
  • Staphylococcus aureus: Yellow colonies; may have yellow halo around colonies.

What chemical ingredient makes MSA selective?

Mannitol salt agar is selective due to the presence of 7.5% sodium chloride (NaCl).

36 Related Question Answers Found

Why is MacConkey Agar yellow?

All lactose fermenters on MacConkey agar also ferment sorbitol. The bacteria grew on mannitol salt agar fermenting mannitol, as shown by the change to yellow of the medium. The pH indicator in mannitol salt agar is phenol red, which turns to yellow when the medium is acidified by the products of fermentation.

Does E coli grow on MSA?

Tryptic soy agar (TSA) inoculated with (A) Staphylococcus aureus, (B) Staphylococcus epidermidis, and (C) Escherichia coli demonstrating growth of all three organisms. TSA is a general purpose medium that will allow for the growth of all three organisms. aureus, while the mannitol nonfermenting colony (pink) is S.

What would be the likely consequences of omitting the NaCl IN MSA agar?

It increases validity because it shows that gram - bacteria are viable (they CAN grow on regular media, but not in salt). What would be the likely consequences of omitting the NaCl in Mannitol Salt Agar? Non-staphylococcus bacteria would be able to grow on the media.

Can gram negative bacteria grow on MSA?

Psuedomonas aeruginosa (Gram negative) - no growth
Mannitol Salt Agar (MSA) is used to determine if the bacteria is halophilic (salt loving) and if the bacteria can ferment mannitol. If the bacteria is able to grow then it is a halophilic bacteria, due to it's ability to grow in a high salt environment.

What is the role of sodium chloride in MSA and how does it work?


Sodium chloride is used in MSA to provide the essential fermentation substrate. It limits the growth of most organisms apart from bacteria in mixed specimens. The salt causes the selectivity nature of the medium used in the specimen. Also, sodium chloride indicates fermentation after the color change.

Is MacConkey agar selective or differential?

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. Lactose provides a source of fermentable carbohydrate, allowing for differentiation.

Can Streptococcus grow on MSA?

Both streptococcal organisms are catalase negative and beta-hemolytic on sheep blood agar plates. Also, neither would grow on the mannitol salt agar. Streptococcus pyogenes is sensitive to growth inhibition by bacitracin, whereas Streptococcus agalactiae (group B streptococci) is not.

Does Staphylococcus aureus grow on EMB agar?

Some strains of Salmonella and Shigella may fail to grow on EMB Agar. Some gram-positive bacteria, such as enterococci, staphylococci, and yeast will grow on this medium and usually form pinpoint colonies. Non-pathogenic, non-lactose-fermenting organisms will also grow on this medium.

Does S epidermidis grow on MSA plate?

Staphylococcus epidermidis grows on MSA, but does not ferment mannitol (media remains light pink in color, colonies are colorless).

What does a red color symbolize in a MSA plate?


The change of its color to yellow due to the acidic pH attained by mannitol utilization by Staph aureus through phenol red indicator in the medium, the red color means pH is again resuming to alkaline with time and is because of the oxidative decarboxylation of the proteins present in the medium by the staph with time.

Why is MSA selective and differential?

MSA is a Selective Medium because of its high (7.5%) sodium chloride concentration that inhibits the growth of most organisms. MSA is a Differential Medium because of the presence of the sugar mannitol and the pH indicator Phenol Red.

What grows EMB Agar?

Eosin methylene blue agar (EMB) is a selective and differential medium used to isolate fecal coliforms. Eosin Y and methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH; they also serve to inhibit the growth of most Gram positive organisms.

Can E coli grow on MacConkey Agar?

Lac positive
By utilizing the lactose available in the medium, Lac+ bacteria such as Escherichia coli, Enterobacter and Klebsiella will produce acid, which lowers the pH of the agar below 6.8 and results in the appearance of pink colonies.

Does sample m contain Staphylococcus aureus?

Does sample M contain staphylococcus aureus? Why or why not? Yes, the sample results are completely identical.

What is DNase test?


DNA hydrolysis test or Deoxyribonuclease (DNase) test is used to determine the ability of an organism to hydrolyze DNA and utilize it as a source of carbon and energy for growth.

What media does Staphylococcus aureus grow on?

Staph. aureus will grow on general culture media such as Blood Agar and chocolated Blood Agar and therefore can be isolated from direct plating of clinical specimens. More specialised media, such as Staph/Strep Selective Medium contain antimicrobials.

What is the application of MSA quizlet?

What is Mannitol Salt Agar (MSA) used for? Isolation and differentiation of Staphylococcus aureus. What does the Mannitol contained in MSA do? Provides the substrate for fermentation and makes the medium differential.