What are selective culture media?

What are selective culture media?

Selective Medium : examples include Salt Mannitol Agar and SS Agar, used to select the species that will be isolated and prevent the growth of germs. Differential Medium : promotes a change in the color of bacterial colonies, enabling the distinction of various genera and species of microorganisms.

What are the characteristics of an ideal culture medium?


Culture media that contain solidifying agents are considered solid; Semi-solids have an intermediate consistency, as they are composed of an amount of agar and/or gelatin that varies from 0.075 to 0.5%; Those that do not contain solidifying agents and have a broth-like appearance are determined…

What are the main means of culture?

Main culture media used and their applications

  • Nutrient Agar.
  • CLED Agar – Cystine Lactose Electrolyte Deficient.
  • Agar Mueller Hinton.

What are the main components of a culture medium?

The main components of a culture medium are sources of carbon, energy (sugars), nitrogen, phosphorus and mineral salts.

What are the types of culture media?

What are the types of culture media ?

  • Liquids or broths: indiscriminate growth with turbidity of the medium ;
  • Solids: growth of isolated colonies, widely used for pure cultures ;
  • Semi-solid: addition of a smaller amount of agar, bacterial mobility;

What are the types of Agar?

Some culture media

  • Blood agar : non-selective medium, growth of gram – e + bacteria
  • Chocolate agar : nutrient medium for most bacteria.
  • Thayer-martin agar : selective medium used to isolate Neisseria, inhibits most other bacteria.
  • MacConkey Agar : Gram-selective, inhibits growth of Gram+ bacteria

How is the culture medium made?

culture medium can be synthetic, with chemically defined components, or complex, when substances from nature are added (meat extract, peptone, blood, among others). As for the physical state, it can be liquid (broth) or solid (broth with 1.5% to 2% agar).

What culture media are used to grow fungi?

The function of the Agar Sabouraud nutrient medium is the cultivation and qualitative growth of fungi , such as filamentous, yeast, candida species and fungi associated with artificial infections.

How to prepare sabouraud culture medium?

Preparation: Suspend 65g of powder in 1 liter of distilled or deionized water. Heat until it boils and dissolves completely. Sterilize in an autoclave at 121°C for 15 minutes. Dispense into final containers.

How to sow in culture medium?

Procedure – Seed the material or microbial culture with the aid of a nickel chromium loop, making sequences of streaks on the surface of the culture medium in the Petri dish, as shown in the figure to the side. Start by transferring the material to the medium (“Initial Exhaustion”).

What are the ways to sow?

Straight Streak: sow with a bacteriological needle, making a straight line, being careful not to injure the Agar, starting from the base to the end of the bevel (inclined surface in the middle). Objective: obtaining a small mass of microorganisms. Central Sting: sow with a bacteriological needle, in the center of the Agar.

What seeding methods in the clinical laboratory?

Among the most used sowing techniques in microbiology, we can mention depletion. In it, the bacterial suspension (which is the liquid with the microorganism) is spread randomly across the entire plate, until all the material is used.

How is colony counting on plates performed?

If the 0.3 ml aliquot plates show more than 300 colonies each, the colonies on the plate containing the 0.1 ml aliquot are counted and multiplied by 100 or 102. Example 120 colonies multiplied by 100 is equal at 12000UFC or 1.2 X 104 UFC of Staphylococcus aureus per gram or milliliter of sample.

How are Ufcs calculated in plate count?

Example: Plate area : 56 cm22 Highest dilution inoculated: 10-3 Square 1: 35 colonies Square 2: 40 colonies Square 3: 32 colonies Square 4: 37 colonies 35 + 40 + 32 + 37 = 144 / 4 = 36 CFU per cm2 36 x 56 x 1.

What does colony count greater than 100,000 cfu mL mean?

Samples with growth of microorganisms whose colony count was equal to or greater than 100.

How to count bacteria in plaque?

To perform the total count of bacteria in a given sample suspension, serial decimal dilutions of the specimen are made and inoculated, usually, in Depth or Incorporation (Pour-Plate) or by the spreading method on a plate with a Drigalsky loop, in media appropriate culture.

What is inoculate in microbiology?

What is inoculation of microorganisms and what is an inoculant? Microorganism inoculation is nothing more than adding beneficial microorganisms to plants . These microorganisms bring some advantages to crops such as: increased growth, better development and improved nutrient absorption.

What is Total Bacterial Count?

The total bacterial count (CBT) The Total Bacterial Count indicates the bacterial contamination of the milk and reflects the hygiene of obtaining and preserving it. It is expressed in colony forming units per milliliter (CFU/mL).

How to count microorganisms?

The method of total counting of food microorganisms using plates is based on plating aliquots of the homogenized food and its dilutions, where the Standard Counting Agar culture medium is used .

What are the main methods used to count microorganisms?

Counting microorganisms in petri dishes with culture media is one of the most used methods in laboratories, and helps to determine the true size of a bacterial population.

What are the direct methods for quantifying microbial growth?

Direct Methods Counting under a microscope; • Counts with culture; Electronic counting.

How to calculate most likely number?

The determination of the most probable number (MPN) of coliforms in a sample is carried out using the multiple tube technique. The method assumes that the bacteria present in a sample can be separated by shaking, resulting in a suspension of cells, evenly distributed.

What is NMP G?

The NMP method allows you to calculate the number of a specific microorganism in a water sample using probability tables. Decimal dilutions of the sample are inoculated into a series of tubes containing selective liquid medium. Tubes are positive when they have growth and/or production of fermentation gas.

What culture medium is used for the confirmatory total coliform test?

Two official methodologies were applied to detect total coliforms Escherichia coli. The Violet Bile Lactose Red Agar (VRBA) medium was used , followed by confirmatory tests and the Petrifilm EC system, manufactured respectively by the companies Oxoid and 3M.

What are thermotolerant coliforms?

What are thermotolerant (fecal) coliforms? These are bacteria that have the ability to use lactose as a nutrient, producing gas at a temperature of 44-45.5 ºC. 90% of Escherichia coli correspond to this group.

Why are fecal coliforms called thermotolerant?

Coliforms are groups of bacteria that indicate contamination and are formed by the genera Escherichia, Citrobacter, Enterobacter and Klebsiella. … There are also Fecal Coliforms , also called Thermotolerant Coliforms as they tolerate temperatures above 40ºC and reproduce at that temperature in less than 24 hours.

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