Question

Using a pipette 30 μL of “3.3× strength isosensitised broth” was added to each well to ensure that the final volume was single strength of the nutrient broth， what mean about “3.3× strength isosensitised broth”，how to prepare it？？and what mean about single strength of the nutrient broth？？？？

Answer 1

NUTRIENT BROTH

A general-purpose liquid medium composed of nutrients (e.g. beef extract and peptone) which allows many types of microorganisms to grow for in vitro experiments such as antibiotic testings on bacteria etc.

Microorganisms are grown on culture media in vitro. These media may be solid media, semisolid media and liquid media. These are prepared according to the purpose of growing microorganism. The nutrient medium is prepared for growing bacteria in vitro i.e. in laboratories. It contains several ingredients as per the requirement including a nitrogen source, proteins source, water, and NaCl. Agar is used as a solidifying agent in media preparation. Nutrient liquid medium can be prepared without adding agar. If agar is added to the nutrient medium, the medium is called nutrient agar medium. If agar is not added to the nutrient medium, then it is known as a nutrient liquid medium or a nutrient broth ( Nutrient soup). so, the key difference between nutrient agar and nutrient broth is that nutrient agar contains agar where as nutrient broth does not contain agar.

In general, nutrient Broth contains peptone, yeast extract, beef extract, NaCl, and water. Nutrient Broth ( liquid medium) is prepared to grow a wide variety of bacteria.

Ingredients

Ingredient	1 L
Distilled water	1 L
beef extract	1 g
Yeast extract	2 g
Peptone	5 g
Sodium chloride (NaCl)	5 g

Iso sensitest medium:

These are prepared to minimize the variable amounts of nutrients and maximize the defined componants. E.g. the divalent cations such as Ca⁺⁺ and Mg⁺⁺ are well known antagonist of aminoglycosides. This type of antagonism is complex and cannot be calculated by the concentration of cations in the medium and also affected by the presence of other constituents such as sodium chloride and phosphates. Traditional medium has variable concentrations of these but in isosensitest medium their concentration is defined in the formulation. So the scientists are able to perform their experiments accordingly.

Strength of nutrient broth:

For marketing or storage purposes the broth is prepared in concentrated forms by using less amount of distilled water. Like 2x (Double strength), 10x (Deca Strength) etc. So here 3.3x strength is simply showing 3.3 times concentrated broth.