Would Omitting The NaCl Alter The Medium Specificity Or Sensitivity?

What is the application of he Agar?

Hektoen Enteric Agar (HE) is a selective and differential medium designed to isolate and differentiate members of the species Salmonella and Shigella from other Enterobacteriaceae.

Bile salts and the dyes bromthymol blue and acid fuchsin inihibit the growth of most Gram positive organisms..

What is the application of 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.

What is the role of sodium chloride in MSA?

Sodium chloride is used in MSA to provide the essential fermentation substrate. It limits the growth of most organisms apart from bacteria in mixed…

Would removal of the bile salts alter the medium’s specificity or sensitivity?

So if bile salts are removed, the medium will become less selective as gram positive and non-pathogenic coliform will also grow. This will DECREASE SPECIFICITY (specificity in this case is ability of HE agar to rule out non causative organism and removal of bile salt will allow growth of non causative organism).

Why is mannitol salt agar used in hospitals?

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.

Why does mannitol salt agar turn yellow?

Mannitol Salt Agar (MSA) is a selective and differential medium. … If an organism can ferment mannitol, an acidic byproduct is formed that will cause the phenol red in the agar to turn yellow. Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol.

Why does EMB inhibit gram positive?

Most bacteria that ferment lactose form colonies on EMB agar that are dark blue to black with a metallic sheen due to precipitation of the dyes by the acid by-products of fermentation. … The growth of Gram positive bacteria is generally inhibited on EMB agar because of the toxicity of methlyene blue dye.

What purpose does the nutrient agar plate serve?

Nutrient agar plates are used to grow colonies of bacteria so that their growth and development can be contained and observed in a laboratory.

What would be the effect of removing the mannitol from mannitol salt agar plates?

Many pathogenic strains of Staphylococcus are able to do this. Other strains that cannot ferment the mannitol do not turn the indicator yellow. Thus, if we remove the mannitol from the plates, we will still be able to select for the Staphylococcus genus, but we cannot differentiate between strains of this genus.

What is the role of phenol red in the mannitol salt medium?

If an organism can ferment mannitol, an acidic byproduct is formed that causes the phenol red in the agar to turn yellow. It is used for the selective isolation of presumptive pathogenic (pp) Staphylococcus species.

Is blood agar selective or differential?

In Blood Agar, blood is added to media after autoclaving (heat sterilization). This medium can be made selective by the addition of antibiotics. This medium is differential because: Blood Agar tests for the production of hemolysin which breaks down red blood cells.

Is MacConkey Agar complex or defined?

Nutrient broth, tryptic soy broth, and chocolate agar, are all examples of complex media. Selective media are used for the growth of only selected microorganisms. An example of a selective medium is MacConkey agar (Table 9.1 & Figure 9.26).

What is the carbon source in mannitol salt agar?

Enzymatic digest of casein, enzymatic digest of animal tissue, and beef extract provide the nitrogen, vitamins, and carbon in Mannitol Salt Agar. D-Mannitol is the carbohydrate source. In high concentrations, sodium chloride inhibits most bacteria other than staphylococci. Phenol red is the pH indicator.

What ingredient makes mannitol salt agar differential?

sugar mannitolThe differential ingredient in MSA is the sugar mannitol. Organisms capable of using mannitol as a food source will produce acidic byproducts of fermentation that will lower the pH of the media. The acidity of the media will cause the pH indicator, phenol red, to turn yellow.

Is E coli gram positive?

Escherichia coli (commonly abbreviated E. coli) is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms).

Would removal of sodium chloride from MSA alter the medium’s sensitivity or specificity explain your answer?

Answer and Explanation: Yes, the removal of sodium chloride from MSA will alter the medium’s sensitivity or specificity to a great extent.

What ingredients are in MSA carbon?

The ingredients in Mannitol Salt Agar (MSA) which supplies: (a) Carbon: Proteose peptone, beef extract, and d-mannitol.

What would be the likely consequences of omitting the salt NaCl in the mannitol salt 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.

What type of medium is blood agar?

Blood agar is an enriched, bacterial growth medium. Fastidious organisms, such as streptococci, do not grow well on ordinary growth media. Blood agar is a type of growth medium (trypticase soy agar enriched with 5% sheep blood) that encourages the growth of bacteria, such as streptococci, that otherwise wouldn’t grow.

What ingredient makes EMB selective?

Eosin Methylene Blue (or EMB) Agar is a Selective & Differential Medium. The selective and differential aspects are due to the dyes Eosin Y and Methylene Blue, and the sugars lactose and sucrose in the medium. It is Selective because it encourages some bacteria to grow while inhibiting others.

What is the purpose of mannitol salt agar quizlet?

What is the purpose of the Mannitol Salt Agar? to presumptively identify Staphylococcus aureus and select for the growth of salt tolerant bacteria. What is a selective medium? A type of media that inhibits the growth of certain bacteria while allowing the growth of another.